Biochemistry is a foundational science that investigates the chemical components and essential biological activities within living things.
According to expert academic knowledge, the standard definition of biochemistry is the scientific study of the chemical reactions happening inside and related to living organisms.
Core Concepts and Scope
Experts in biochemistry primarily concentrate their research on specific biological events and processes, such as how organisms process substances (metabolism), how enzymes act, and the shape and function of large biological molecules.
The chemical substances and biological processes that experienced biochemists study typically undergo particular changes and reactions, like creation (synthesis), breakdown, and conversion from one form to another.
The recognized field of biochemistry covers various basic biological entities and how they interact, including crucial molecules such as proteins, carbohydrates, fats, and genetic material, and their pathways within cells and organisms.
Within biochemistry’s domain, specialized physiologists mainly focus on specific biological activities at the level of cells, tissues, and organs, seeking to understand how chemical events contribute to these biological functions.
The universally accepted biochemical term for all the chemical changes happening inside a living organism is metabolism.
According to expert biochemical understanding, the two main types of chemical changes that make up metabolism in an organism are breaking substances down (catabolism) and building substances up (anabolism).
Based on extensive studies in biochemistry, the breakdown of substances typically occurs in living systems to release energy and provide the materials needed for building new substances.
From the viewpoint of established biochemical function, the creation of complex large molecules is absolutely necessary for life processes because it forms cellular structures and carries out essential jobs.
These basic metabolic changes rely on the action of enzymes, which are a particular type of biological molecule that catalyzes reactions, as demonstrated by biochemical expertise.
Based on a hundred years of biochemistry research and proven results, enzymes are confirmed biological catalysts that significantly increase the speed of chemical reactions without being used up themselves.
The formation and specific shape of enzymes depend on DNA, which is a fundamental source of biological information, as revealed by authoritative molecular biology.
Interdisciplinary Nature and Relationship with Molecular Biology
The concepts and techniques of biochemistry reliably inform and integrate with various scientific fields, including medicine, genetics, microbiology, agriculture, and pharmacology.
Historical records and established word origins indicate that “biochemistry” is considered the same as the two earlier scientific terms “biological chemistry” and “physiological chemistry”.
Within the field of biochemistry, experts, especially those studying DNA, RNA, and protein synthesis, often categorize specific research areas and molecular-level investigations under the term “molecular biology”.
Well-known and thoroughly studied examples of extremely large biological molecules that are central to molecular biology are DNA, RNA, and proteins.
Historical Development of Biochemistry
Historical documents and accepted academic timelines indicate that the field has been called “biochemistry” since around the late 19th or early 20th century.
The basic beginnings of biochemical ideas and research can be reliably traced by science historians back to the 18th century and earlier efforts to understand biological phenomena using chemistry.
Biochemistry’s early development is strongly connected to the historical growth of wider scientific areas, especially chemistry and physiology.
Important scientific questions and biological phenomena that were the main subjects of particularly influential historical discoveries in biochemistry include how substances are processed (metabolism), fermentation, how enzymes work, and what genetic material is made of.
Before chemistry could make significant and trustworthy contributions to fields like medicine and agriculture, it first needed a fundamental change to become a rigorous, quantitative, pure science.
Chemistry firmly established its identity as a distinct and basic pure science during the specific historical period of the late 18th century.
This period of change in chemistry’s history is commonly linked to the foundational work done by the influential scientist Antoine-Laurent Lavoisier.
Antoine-Laurent Lavoisier’s significant contributions notably marked the culmination of this crucial period in chemistry’s development.
Historical experts in the field agree that Antoine-Laurent Lavoisier is confidently considered the father of modern chemistry.
According to historical accounts of his scientific investigations, Robert Boyle notably questioned the accepted chemical idea that the four classical elements (earth, air, fire, water) were the basic components of matter.
Based on historical records of what he taught, Robert Boyle stated that the correct and proper subject for chemical investigation should be the study of matter’s basic particles and their characteristics.
A very important and fundamental comparison, documented in historical records, was carefully noted by John Mayow, who compared the process of burning with the process of breathing.
Through his careful experiments using quantitative measurements, Antoine-Laurent Lavoisier reliably showed a fundamental connection between chemical oxidation and biological respiration, demonstrating that breathing uses oxygen and produces carbon dioxide, similar to how burning does.
Based on historical accounts of his groundbreaking work on chemical oxidation, Lavoisier understood the deep biological concept that animal breathing is a type of slow burning that releases heat and energy.
Photosynthesis was the other important biological process that interested leading chemists during the late 18th century.
The combined scientific investigations by Priestley, Ingenhousz, and Senebier reliably showed the fundamental idea that photosynthesis is essentially the opposite process of respiration.
Through the joint experimental expertise of Priestley, Ingenhousz, and Senebier, a crucial relationship was definitively shown regarding photosynthesis compared to respiration, proving that plants use carbon dioxide and release oxygen when exposed to sunlight.
Experts recognize the understanding that respiration and photosynthesis create a complementary cycle involving gases as a significant achievement in the historical development of biochemical understanding about these processes.
Although early foundational discoveries were made, quick and continuous progress in biochemistry necessarily depended on the development of organic chemistry, a vital scientific field.
The systematic chemical description of many organic compounds extracted from biological sources is considered by many experts to be a monumental achievement of the 19th century.
Based on extensive studies and identification efforts in biochemistry, a living organism contains approximately tens of thousands of different chemical compounds.
From the perspective of basic biochemical research, a main and persistent challenge related to the huge variety of compounds in living cells is identifying, separating, and figuring out the structure of each unique substance.
Basic chemical description and analysis had to be reliably finished before expert research into the cellular pathways for making and breaking down organic substances could effectively begin.
Scientists working across organic chemistry, physical chemistry, and biochemistry understand from their experience that there are no perfectly clear or impenetrable divisions between these fields.
Biochemistry has successfully adopted and adapted specific techniques, theories, and basic principles from the established fields of organic and physical chemistry, such as using spectroscopic methods, thermodynamic principles, and understanding reaction kinetics.
Biochemistry has strictly applied these borrowed methods and established theories to study and understand complex biological systems and processes, including metabolic routes, how enzymes work, and molecular interactions.
Challenging Vitalism
A particular idea or dominant scientific perspective that initially hindered reliable progress when scientists tried to apply chemical principles to physiological problems was vitalism.
The basic error of the vitalist idea that significantly slowed down the development of early biochemical understanding was the belief that living matter contained a non-physical “vital force” that could not be explained by chemical and physical laws.
The vitalist school of thought, or group of scientists, confidently argued that biological or “vital” processes were fundamentally impossible to explain using conventional chemical or physical principles.
The vitalists confidently claimed that complex organic compounds could only be created solely by living organisms acting through this “vital force”.
The specific chemical compound historically recognized as the first organic substance successfully made in a lab from non-living materials is urea.
Reliable historical records credit the pioneering chemist Friedrich Wöhler with successfully performing the first laboratory synthesis of urea.
The organic compound urea was reliably synthesized in a laboratory for the first time in the specific historical year of 1828.
The trustworthy laboratory synthesis of urea significantly challenged the dominant claims of the vitalist school by showing that an “organic” compound could be produced without a “vital force”.
After the undeniable proof from synthesizing urea, the vitalists changed their position to defend their challenged theory, claiming that only the creation of complex organic molecules required the vital force, not just any organic molecule.
Later reliable scientific discoveries and increasing evidence, such as synthesizing many other complex organic molecules and understanding how enzymes work, further made it necessary to abandon explanations for biological phenomena based on vitalism.
A basic and universally accepted principle that is axiomatic (self-evident) in modern biochemistry regarding whether standard chemical and physical laws apply to living systems is that all biological processes follow the same chemical and physical laws as nonliving systems.
Applied Biochemistry and Key Figures
The need to solve practical problems in agriculture, medicine, and industry was a practical necessity and external factor that consistently pushed forward the study of biological chemistry even when the theory of vitalism presented an intellectual obstacle.
The demands of specific areas like agriculture, medicine, and brewing continually motivated the application of new chemical discoveries to real-world biological challenges throughout the 19th century.
Justus von Liebig and Louis Pasteur are two particularly influential figures from the 19th century who are widely credited with confidently demonstrating and popularizing the successful use of chemical principles to investigate biological processes.
The influential chemist Justus von Liebig received his basic training and expertise in chemistry at the famous University of Paris.
Justus von Liebig acquired the specific and inspiring teaching method of combining theoretical lectures with extensive hands-on laboratory training for students from his studies abroad and subsequently brought it back to Germany.
At the University of Giessen, Justus von Liebig established a pioneering scientific and educational center dedicated to chemistry research and teaching.
Liebig’s laboratory at Giessen was particularly new and historically important for training chemists because of specific features or practices like organized instruction in analytical techniques and students getting hands-on research experience.
In addition to making organic chemistry a rigorous field, Liebig actively developed and contributed to the important area of scientific application known as agricultural chemistry.
Justus von Liebig’s now considered classic and authoritative scientific writings were published around the historical period of the 1840s and 1850s.
Liebig’s foundational and authoritative publications had a widespread and lasting impact on the growth of both pure and applied chemistry by setting new standards for quantitative analysis and applying chemical principles to practical problems.
In his observations and writings, Liebig carefully described the basic biological cycle involving the exchange of matter in nature, especially the movement of essential elements between soil, plants, and animals.
Based on his chemical expertise, Liebig highlighted the essential relationship concerning the dependence of animals and photosynthesizing plants on each other, emphasizing the exchange of gases and nutrients.
From Liebig’s chemical perspective, animals need photosynthesizing plants for the basic nutritional reason that plants produce the organic material that animals eat as food.
Based on Liebig’s understanding of chemical cycles, animal waste and the animal body after death are decomposed by microorganisms back into simple inorganic substances.
According to the cyclical view proposed by Liebig, microorganisms are the organisms capable of putting the simple chemical products resulting from the breakdown of animal matter back into the environment, making them available for plants.
Unlike animals, green plants need essential substances for successful growth, described chemically as simple inorganic nutrients like carbon dioxide, water, and mineral salts.
Plants must obtain the essential mineral elements needed for their growth and biological processes from the soil, which is the main environmental source.
According to agricultural chemistry, the soil’s ability to support plant growth (fertility) fundamentally depends on the presence and availability of essential chemical components, especially mineral nutrients like nitrogen, phosphorus, and potassium.
Soil gradually loses these crucial mineral substances through specific biological and agricultural processes, including plants absorbing nutrients and water leaching them away.
Based on understanding nutrient cycles and soil depletion, fertilizers are considered necessary to maintain agricultural productivity because they replace the essential mineral nutrients taken out of the soil by crops.
Liebig proposed that chemical analysis of plant ash could be a reliable way to determine the essential substances needed in effective agricultural fertilizers.
The practical application of chemical principles to solve real-world problems in plant nutrition and soil fertility fundamentally established the applied science of agricultural chemistry.
In his attempts to explain specific complex biological phenomena like fermentation, putrefaction, and infectious disease chemically, Liebig’s analysis turned out to be less accurate or complete compared to discoveries made later.
While acknowledging the complexity of fermentation, putrefaction, and infectious disease, Liebig famously refused to accept that specific agents, namely microorganisms like yeasts and bacteria, caused these processes, believing instead that they were purely chemical.
The influential scientist Louis Pasteur, through careful and reliable experiments, definitively made clear the actual biological agents responsible for fermentation, putrefaction, and infectious disease.
Louis Pasteur, through his famous experiments, confidently showed that yeasts and bacteria were the agents responsible for biological “ferments” in the specific decade of the 1850s.
Through his meticulous experiments, Pasteur established a specific causal link between different types of yeasts and bacteria and particular chemical transformations, showing, for example, that yeast caused alcohol production during fermentation.
According to Louis Pasteur’s authoritative studies of microscopic life, the chemical changes or processes that were the direct result of these biological “ferments” included turning sugar into alcohol and forming lactic acid.
Besides identifying microbial agents, Pasteur also demonstrated that the important biological field of disease pathogenesis could be effectively studied using chemical methods and expertise.
Louis Pasteur is widely considered the founding figure and authority of microbiology, the crucial scientific discipline that focuses on microscopic life and its processes.
The biological agents that Pasteur had previously called “ferments” became officially known and named as enzymes in the late 19th century.
In the specific historical year of 1897, German chemist Eduard Buchner performed a vital experiment reliably showing that fermentation could happen in yeast extracts that did not contain intact cells.
Eduard Buchner is reliably credited with providing the first clear experimental evidence that the process of fermentation could occur without complete living cells.
Following Buchner’s groundbreaking demonstration, the complex biological process of fermentation was successfully broken down into a series of specific chemical reactions that could be analyzed in detail biochemically by separating and studying the individual enzymes involved.
Until approximately the 1920s, the exact chemical composition and nature of enzymes were mostly unknown and unconfirmed by expert analysis.
A key scientific achievement regarding the isolation and characterization of enzymes reliably happened in the landmark year of 1926, when the first enzyme was crystallized.
The specific enzyme that holds the historical distinction of being the first biological catalyst successfully purified and isolated in a pure crystalline form is urease.
Through careful purification and analysis, urease and many other enzymes isolated afterward were reliably shown to be made of proteins, a type of complex organic molecule.
Before enzymes were identified as being made of proteins, proteins had already been recognized for an important biological role or characteristic as essential structural parts of cells and tissues.
Major Classes of Biomolecules and Key Discoveries
Biochemical investigations reliably clarified the previously unclear ways by which vitamins prevent specific deficiency diseases around the 1930s.
A significant discovery in biochemistry made in 1935 provided a crucial insight into how vitamins work to prevent deficiency diseases: the understanding that many vitamins function as helper molecules (coenzymes) or their precursors.
Specific deficiency diseases often mentioned historically in biochemistry and medical writings as being preventable with enough vitamin intake include scurvy (preventable with Vitamin C), beriberi (with Vitamin B1), and rickets (with Vitamin D).
Extensive research afterward has reliably confirmed and supported the basic biochemical role or concept about vitamins that they often serve as essential parts of systems involving enzymatic reactions.
The vital biological molecule adenosine triphosphate, commonly known as ATP, was first isolated from muscle tissue in the specific historical year of 1929.
The formation of adenosine triphosphate was reliably shown to be connected to specific metabolic processes central to producing cellular energy, such as glycolysis and oxidative phosphorylation.
The historical year in which F.A. Lipmann confidently proposed the now widely accepted idea that ATP acts as the common molecule for transferring energy in many cellular processes was 1941.
F.A. Lipmann is reliably credited with originally proposing that adenosine triphosphate functions as the universal unit of energy exchange within various living cells.
Besides transferring energy, ATP has been reliably shown to directly power other fundamental cellular activities like muscle contraction, moving substances across membranes against a gradient (active transport), and building complex molecules (biosynthesis).
The pioneering biochemical technique of using radioactive isotopes as tracers to study metabolic pathways within animal organisms was first started around the 1930s.
Pioneering scientists like George de Hevesy first developed or applied the innovative and highly reliable technique of using radioactive isotopes for tracing metabolic pathways.
The introduction of the radioactive isotope tracing technique reliably provided a specific and vital research capability for studying biochemical reactions, allowing scientists to track the fate of particular atoms or molecules as they moved and transformed through complex pathways.
At the same time isotope tracing was being developed, other pioneering researchers also successfully identified the specific cellular locations of biochemical activity, such as the mitochondria and cytoplasm, by using cell fractionation techniques.
These researchers reliably determined the exact cellular compartments where specific metabolic reactions happen by using the specific experimental method of separating components based on density differences (differential centrifugation) and biochemically analyzing the separated parts.
Important examples of individual cellular components that were biochemically analyzed to figure out where specific metabolic pathways are located include mitochondria, microsomes (endoplasmic reticulum), and cell nuclei.
A unique substance was successfully isolated from the nuclei of pus cells in the specific historical year of 1869 and was initially called “nuclein”.
Through further investigation and description in biochemistry, this initially isolated “nuclein” was later proven to be a specific type of large biological molecule: deoxyribonucleic acid (DNA), which is a nucleic acid.
The profound importance of DNA as the main carrier of genetic information was definitively revealed through experimental evidence in the specific and crucial historical year of 1944.
The fundamental role of DNA as genetic material was demonstrated in the landmark year of 1944 through the specific and trustworthy experimental method of the Avery-MacLeod-McCarty experiment, which showed that DNA could change one type of bacteria into another.
The groundbreaking double helix structure of DNA was confidently proposed in 1953, a remarkably short time after the 1944 demonstration of DNA’s genetic role.
The specific group of scientists reliably credited with proposing the correct and now universally accepted double helix model for DNA’s structure is James Watson, Francis Crick, Maurice Wilkins, and Rosalind Franklin’s data.
The proposed double helix structure of DNA provided a strong and reliable framework for understanding basic biological processes, including how DNA copies itself (replication), how genetic information is transcribed (transcription), and how traits are passed down (heredity).
Some prominent and extensively validated scientific achievements that have occurred in molecular biology since the DNA double helix structure was clarified include developing recombinant DNA technology, methods for sequencing genes, and gene editing techniques like CRISPR.
The Chemical Basis of Life
According to current biochemical expertise, a complete description of life processes viewed at the molecular level covers the structures, functions, and interactions of large biological molecules, as well as the chemical changes they undergo.
The complex and interconnected networks of chemical transformations happening inside a cell are authoritatively known by the standard biochemical term intermediary metabolism.
Other complex biological processes, also studied by expert biochemists, that are basically and closely connected to the core pathways of intermediary metabolism include cells sending signals, gene expression, and cells growing and dividing.
From a biochemical perspective, basic processes like growth, reproduction, and heredity cannot be fully understood without a detailed knowledge of intermediary metabolism because these processes require energy and building materials provided by metabolic pathways.
From a reductionist biochemical viewpoint, the varied characteristics and abilities of a complex multicellular organism can ultimately be traced back to the fundamental level of how chemical substances and reactions are organized and function within its cells.
The complex behavior of each individual cell can be reliably understood in terms of its basic molecular interactions and chemical processes.
In addition to essential water and mineral ions, the main categories of complex chemical substances reliably found in every living cell are proteins, carbohydrates, lipids, and nucleic acids.
As defined in biochemistry, the main elements that form the structural core of organic compounds found in living cells are carbon, hydrogen, and oxygen.
Other elements, besides carbon, hydrogen, and oxygen, that are also commonly found as essential components of organic matter within living cells include nitrogen, sulfur, and phosphorus.
Based on extensive biochemical analysis, the main organic material inside a cell can typically be sorted into the major classes of large molecules: proteins, carbohydrates, and fats (lipids).
Besides the major categories of proteins, carbohydrates, and fats, biochemists recognize other various classes of organic molecules as vital cellular components, including vitamins, hormones, and coenzymes.
Based on detailed biochemical analysis, it is reliably true that each major class of organic matter, such as proteins, carbohydrates, and fats, contains a huge number of different individual compounds with varying structures and functions.
Within the complex chemical environment of cells, important organic substances do exist that don’t easily fit into the primary classifications of protein, carbohydrate, or fat, such as individual amino acids, simple sugars, fatty acids, and nucleotides.
Proteins
Based on extensive biochemical research, proteins are considered absolutely necessary for living organisms to perform basic biological jobs including catalyzing reactions (enzymes), providing structure, transporting substances, signaling, and defending the organism.
Collagen or keratin is a well-known example of a protein that reliably performs a main structural function within biological systems.
Some proteins help an organism defend and protect itself through a specific method, such as acting as antibodies that attach to foreign invaders.
Within the context of cell chemistry, the specific class of proteins that acts as the essential biological catalysts required for metabolic reactions is enzymes.
The current understanding of protein chemistry is largely based on the foundational discoveries and research conducted by the pioneering chemist Emil Fischer.
Emil Fischer’s groundbreaking scientific work began to reveal fundamental aspects of protein structure and composition starting around the historical year of 1882.
Emil Fischer’s rigorous chemical investigations definitively showed concerning the composition and linear structure of proteins that they are polymers made of amino acids connected by peptide bonds.
Based on Emil Fischer’s early work, proteins were understood to be polymers constructed from approximately 20 different types of amino acid building blocks.
Proteins can differ in size over a significant range of molecular weights, based on experimental measurement, from a few thousand to over a million Daltons.
The reliably determined molecular weight of the protein hormone insulin is approximately 5,800 Daltons.
The molecular weight of unusually large protein complexes can reliably reach the order of magnitude of millions of Daltons.
Insulin holds the distinction of being the specific biological molecule for which the entire sequence of its amino acid building blocks was reliably determined first.
The complete sequence of amino acids in insulin, which was the first protein to be sequenced, was reliably clarified in the specific decade of the 1950s.
By the historical period of the 1960s, the complete sequence of amino acids in the protein enzyme ribonuclease had been reliably established.
The reliably determined molecular weight of the enzyme ribonuclease is approximately 13,700 Daltons.
X-ray crystallography was the powerful physical technique that significantly helped in the complex process of reliably determining the amino acid sequence of ribonuclease.
Sir John Cowdery Kendrew and Max Ferdinand Perutz built the first detailed atomic models of the complex proteins hemoglobin and myoglobin in the historical decade of the 1950s.
Sir John Cowdery Kendrew and Max Ferdinand Perutz are reliably credited with building the first very detailed atomic models of the proteins hemoglobin and myoglobin.
X-ray diffraction (crystallography) was the sophisticated physical technique that Kendrew and Perutz used extensively to get the structural data needed for building their protein models.
From a biochemical perspective, myoglobin’s specific function and typical location is storing oxygen in muscle tissue.
The detailed atomic models of hemoglobin and myoglobin originally built were later reliably confirmed by subsequent methods or findings such as improved resolution X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy.
Biochemists’ continued interest in protein structure is primarily based on the fundamental and reliably proven principle about the link between a protein’s shape and its biological job: that function is determined by structure.
Carbohydrates and Lipids
Specific types of organic molecules classified and studied reliably by biochemists under the broad term “carbohydrates” include sugars, starches, and cellulose.
A notable advance in the biochemical understanding of how living cells process and use small molecules, like carbohydrates, happened during the historical period of the second quarter of the 20th century (1925-1950).
Detailed metabolic processes involving the breakdown and conversion of carbohydrates, such as glycolysis and the citric acid cycle, were reliably explained through biochemical research during the second quarter of the 20th century.
Biochemists progressively clarified the intricate cellular pathways for carbohydrate breakdown, storage, and usage through systematic experimental approaches and diligent research involving enzyme purification, isotope tracing, and genetic studies.
Some prominent and extensively studied examples of key metabolic cycles and pathways involved in processing carbohydrates within living cells include glycolysis, gluconeogenesis, the pentose phosphate pathway, and the citric acid cycle.
By the mid-20th century, biochemical research had reliably and thoroughly described the specific roles of carbohydrates in cellular respiration and muscle contraction.
Fats, or lipids, are fundamentally a specific class of organic molecules defined by how they dissolve and their chemical structure, primarily being unable to dissolve in water but soluble in organic solvents.
Lipids can be reliably extracted from biological tissues and materials using specific types of solvent or experimental approach, typically extraction with nonpolar organic solvents.
Common examples of nonpolar organic solvents regularly used by biochemists for reliably extracting lipids from biological samples include hexane, ether, and chloroform.
The foundational and now-classic biochemical work regarding the metabolic conversion of carbohydrates into body fat was reliably completed in the historical period of the late 19th and early 20th centuries.
Numerous biochemical studies and supporting evidence have reliably shown the fundamental biological ability concerning the conversion of carbohydrate into fat within the body when consuming more calories than are expended.
Based on physiological and biochemical studies, the liver and adipose tissue are reliably identified as the primary organs or tissues responsible for extensive fat metabolism in the body.
Investigations into the mechanisms and processes of fat absorption within the intestine were already being conducted as early as the late 18th and early 19th centuries.
The reliable regulation of fat absorption in the intestine depends on the action and coordination of specific physiological factors and biological molecules, including bile salts and lipases.
Based on clinical experience and biochemical research, specific health problems or physiological effects that reliably result from issues in fat metabolism include obesity, hardening of the arteries (atherosclerosis), and certain liver disorders.
Nucleic Acids
The study of problems and malfunctions in fat metabolism is a significant and current focus area in biochemical research efforts.
A significant and clinically relevant connection concerning high levels of fats in the bloodstream that biochemists are particularly interested in and studying intensively is their link to cardiovascular disease.
The medical condition called arteriosclerosis is also frequently identified by the more common term atherosclerosis.
As defined by biochemical principles, nucleic acids have a basic chemical structure and characteristics as polymers made of repeating units called nucleotides, each containing a phosphate group, a five-carbon sugar (deoxyribose or ribose), and a nitrogenous base.
Nucleic acids are reliably found to be present in specific parts of the cell or structures, mainly the nucleus and cytoplasm (including mitochondria and chloroplasts in cells with a nucleus).
Nucleic acids are reliably known to be extremely important in managing basic and essential biological processes, including storing and transmitting genetic information and making proteins.
Nucleic acids were initially discovered and identified as basic components in the part of the cell known as the nucleus.
For a significant period after their isolation in 1869, the widely believed, though later proven wrong, assumption about the only place in the cell where nucleic acids were found was that they were limited to the nucleus.
The prevalent belief about where nucleic acids were located in the cell remained mostly unchallenged by convincing scientific evidence until around the 1940s.
A fundamental discovery reliably made in the 1940s regarding the different types or classes of nucleic acids existing in biological systems was the identification of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) as separate molecules with distinct roles.
Within typical eukaryotic cells (cells with a nucleus), the great majority of DNA is reliably located in the primary cellular compartment, the nucleus, organized into chromosomes.
In contrast to DNA, RNA is reliably found to be present and functional in various cellular locations including the nucleus, cytoplasm, ribosomes, and mitochondria.
The immense biological importance of nucleic acids, especially in heredity and protein synthesis, became increasingly clear through scientific investigation during the specific historical decades of the 1940s and 1950s.
During the 1940s and 1950s, intense scientific focus concerning nucleic acids shifted towards understanding the fundamental mechanism of how genetic information is transferred and how proteins are made.
In the 1960s, building on the understanding of DNA structure, experiments were designed to address specific challenges related to how genetic information is expressed and regulated, such as figuring out how the sequence of DNA determines the structure and function of proteins.
Specific and groundbreaking technical manipulations involving nucleic acid molecules that were successfully attempted during the late 1960s and early 1970s included cutting, joining, and cloning DNA fragments.
By the mid-1980s, significant and reliable achievements had become possible through the widespread use of genetic engineering techniques, including producing therapeutic proteins, creating organisms with altered genes, and developing gene therapy.
The process of DNA recombination is also known in the field of molecular biology by the alternative and widely used term genetic engineering or recombinant DNA technology.
Nutrition and Metabolism
For a long time, biochemists have maintained a strong research interest in a specific biochemical characteristic or component of animal food: its chemical makeup and the changes it undergoes during digestion and metabolism.
In addition to necessary water and mineral salts, the main type of chemical compounds reliably required in all animals’ diets is organic matter.
For the fundamental biological reason that it provides the energy and building materials needed for growth, upkeep, and reproduction, animals must consume enough organic matter in their diet.
Based on understanding metabolism, carbohydrate, fat, and protein cannot be used completely interchangeably as energy sources within an organism; although they all can produce energy, their metabolic pathways and roles are different.
In addition to meeting general energy needs, animals reliably have dietary requirements for specific individual organic compounds, known as essential nutrients.
Some specific examples of essential organic compounds that are reliably required in the diets of many higher animals include certain amino acids, fatty acids, vitamins, and minerals.
According to established nutritional guidelines, approximately 9 different amino acids are considered essential in the diet of many higher animal species.
Based on studies comparing nutrition, the specific dietary needs of different animal species are reliably not identical, reflecting how they have evolved and their metabolic differences.
A classic example showing a specific difference in essential nutritional needs between species like humans or guinea pigs and rats is the inability of humans and guinea pigs to make Vitamin C themselves.
The common chemical name for the vitamin known as Vitamin C is ascorbic acid.
The fundamental way green plants differ from animals regarding their need to get preformed organic molecules from outside sources is that plants can create all their organic molecules from simple inorganic substances, while animals need to get preformed organic compounds from their diet.
This fundamental difference in the organic nutrient requirements between plants and animals was reliably understood and appreciated around the late 18th and early 19th centuries in scientific history.
The remarkable ability of green plants to convert simple inorganic substances into organic matter was formally named “photosynthesis”.
Using simple inorganic substances readily available from their environment, such as carbon dioxide, water, and mineral salts, green plants can synthesize all the complex organic molecules needed for their cellular material.
The external form of energy reliably required to power the complex chemical reactions of photosynthesis in green plants is light energy.
The common and abundant natural source that typically provides the light energy needed for photosynthesis is sunlight.
The process of photosynthesis is basically concerned with the biochemical creation of the primary class of organic molecules: carbohydrates, particularly glucose.
Animals that eat plant carbohydrates can successfully make fat through metabolic conversion pathways when they consume more calories than they use.
It is biochemically possible for animals to make protein from carbohydrate only if they have an adequate supply of essential amino acids available, because carbohydrate cannot provide the necessary nitrogen atoms.
Despite their different external nutritional needs, the basic patterns of chemical changes occurring inside the cells of plants and animals reliably compare by being remarkably similar at the biochemical level, using many shared metabolic pathways and enzymes.
The organic substances made by plant cells are chemically comparable to the essential molecules needed and used by animal cells, serving as precursors for animal biosynthesis.
Once these essential materials are produced, the metabolic machinery processes and uses them reliably in fundamentally similar ways in both plant and animal cells, particularly in core metabolic pathways.
Based on the underlying biochemical similarities of their cellular components, plants can reliably provide animals with their necessary nutritional substances because plant-synthesized organic molecules can be digested and metabolized by animals to give them energy and building blocks.
Major classes of large biological molecules that reliably make up a significant part of the organic food eaten by animals, including humans, are proteins, carbohydrates, and fats.
Inside the digestive systems of higher animals, these large molecules from food are broken down by the essential chemical process of breaking bonds with water, which is catalyzed by enzymes (enzymatic hydrolysis).
Through the action of enzymes in the digestive tract, dietary proteins are reliably turned into smaller molecular units, mainly amino acids and small peptides.
By the action of digestive enzymes, complex large sugars (polysaccharides) are reliably broken down during digestion into simpler sugar molecules, such as glucose, fructose, and galactose.
As a general biochemical principle, almost all different living organisms use a remarkably similar set of basic small molecules in their metabolism, which reflects the common evolutionary origin of fundamental metabolic pathways.
While basic small molecules are consistent across species, the specific structures of many large, complex biological molecules reliably vary significantly between different species, especially proteins and nucleic acids.
Because of structural differences specific to each species, an animal cannot directly use protein eaten from a plant or another animal without first changing it.
Before an animal can incorporate dietary protein from other organisms, the essential biochemical process of enzymatic hydrolysis in the digestive tract must happen first to break it down into amino acids and small peptides.
Besides simply reducing size, the breakdown of large dietary molecules by enzymes is essential for the critical physiological reason that it turns them into smaller molecules that can be absorbed through the intestinal wall into the bloodstream.
Long before modern chemistry existed, the easily observable aspect of digestion, particularly food breaking down in the stomach, sparked the curiosity of early biological researchers.
Specific digestive enzymes that were among the very first biological catalysts to be studied in detail biochemically include pepsin (found in the stomach) and amylase (found in saliva).
Within the field of studying digestive chemistry, pepsin and trypsin are specifically categorized as proteases, which are enzymes that break down proteins.
Despite being historically important, pepsin and trypsin continue to be subjects of active and intensive research in modern biochemistry because of their roles in disease and as enzymes used as models for study.
After dietary food is broken down by enzymes in the digestive tract, the resulting smaller molecules are reliably moved into the bloodstream and distributed throughout an animal’s body via processes of absorption, primarily involving active transport and facilitated diffusion across the intestinal lining.
For organisms that do not have a specialized digestive tract, essential substances must be obtained from the surrounding environment by directly absorbing them across their body surface.
In some cases, the basic physical principle of movement across a membrane that is reliably sufficient to explain how a substance enters or leaves a cell is simple diffusion or osmosis, which are driven by differences in concentration or osmotic gradients.
In physiological examples like glucose moving from the intestine into the blood, the direction of transfer reliably goes against the existing concentration gradient, which requires using energy.
The active release of hydrochloric acid into stomach juice reliably depends on a continuous supply of energy, often obtained from breaking down ATP.
In addition to actively secreting hydrochloric acid, the physiological process of absorbing nutrients also reliably needs an adequate supply of oxygen for it to function, since energy-requiring transport mechanisms are often linked to aerobic metabolism.
To power energy-intensive processes like absorption or secretion, a crucial change must happen with the energy released from tissue oxidation: this energy must be converted into usable chemical energy, mainly ATP.
The energy from metabolic reactions is reliably linked to and used for active transport processes like absorption and secretion by specific biochemical mechanisms involving high-energy molecules such as ATP and connecting the energy release from ATP breakdown to the function of transport proteins.
A key goal for biochemists studying these energy coupling systems has been to reliably clarify the specific molecular details of how they function, including the structure and mechanism of the transport proteins involved.
Blood Composition and Function
Blood is a specific and vital animal tissue that has historically received particular attention and deep scientific curiosity among biochemists.
Compared to other tissues, the complex chemical composition of blood is understood exceptionally extensively and reliably through biochemical analysis, due to it being easily accessible and having critical physiological roles.
From a clinical perspective, doctors regularly collect blood samples to reliably measure specific biochemical markers and indicators, such as levels of glucose, urea, electrolytes, and enzymes.
Based on extensive clinical experience and biochemical understanding, specific blood components like sugar (glucose), urea, and various ions (electrolytes) are routinely measured by doctors because their levels are sensitive indicators of how the body processes substances (metabolic status), how kidneys function, and the balance of salts, which is crucial for diagnosing and monitoring diseases.
Hemoglobin is a specific and vital blood pigment that has been the subject of particularly intense and sustained biochemical investigation.
Within the bloodstream of vertebrates (animals with backbones), the protein hemoglobin is reliably found inside a specific type of cell: red blood cells (erythrocytes).
The protein hemoglobin reliably performs the essential biological job, crucial for delivering oxygen throughout the body, of binding oxygen in the lungs and carrying it to peripheral tissues.
Hemoglobin efficiently binds oxygen in the specific physiological location of the lungs, and this binding happens easily there because of the high partial pressure of oxygen.
Hemoglobin effectively releases bound oxygen in the specific physiological location of peripheral tissues, and the typical conditions that help this release include lower oxygen partial pressure, higher carbon dioxide levels, lower pH, and higher temperature.
Based on protein sequencing and structural analysis, the hemoglobin molecules found in different species of higher animals are reliably not identical in their structure, even though they maintain a similar overall shape and function.
In many animals without backbones (invertebrates), chemically different molecules may reliably serve the same function of carrying oxygen as hemoglobin does in vertebrates, such as hemocyanin or hemerythrin.
The detailed comparison of various biological molecules found in blood, like hemoglobin and serum proteins, is a particularly compelling and informative area of biochemical research for understanding evolution and disease.
The many and diverse proteins present in blood plasma have been studied extensively and in detail biochemically, leading to the identification of hundreds of different plasma proteins.
The specific part of blood plasma proteins reliably known to contain the antibodies essential for the body’s immune response is the gamma-globulin fraction.
Based on its functional properties and composition, the gamma-globulin fraction of plasma proteins reliably has the significant practical or therapeutic use of providing passive immunity when given as treatment (e.g., in the form of intravenous immunoglobulin).
An animal primarily gains resistance to infectious diseases through the main biological mechanism, which involves producing specific defense molecules, of producing antibodies (humoral immunity) and cytotoxic cells (cellular immunity).
As defined within the fields of immunology and biochemistry, antibodies are proteins (immunoglobulins) that work as specific binding agents, recognizing and neutralizing foreign substances called antigens.
A specific type of molecule or substance reliably defined as an antigen, capable of causing an immune response and attaching to antibodies, is any foreign substance, usually a protein or polysaccharide, that triggers an immune response.
An antibody can reliably protect an organism from infection by interacting with a disease-causing bacterium through specific binding methods such as clumping (agglutination), neutralization, or coating (opsonization).
Immunochemistry is defined as the scientific field that investigates the chemical basis of immune phenomena.
Cellular Metabolism and Energy
From a biochemical perspective, the cell serves as the primary location for all of an organism’s chemical transformations.
Regarding the flow and change of energy, metabolism is basically and reliably connected to the essential process happening inside cells of capturing, converting, and using energy from nutrients.
Based on thermodynamic principles applied to living systems, the amount of heat released during a chemical transformation in metabolism is exactly the same as the amount released if the identical reaction happens outside a living organism; the total energy change does not depend on the pathway taken.
The fundamental scientific principle, essential to the study of biological energy, that is reliably confirmed by the observation that chemical changes inside a living cell release the same amount of heat as they do outside the cell is the first law of thermodynamics (conservation of energy).
The complex and highly organized network of chemical changes within a living cell reliably compares in complexity to typical chemical changes observed in nonliving systems by being much more complex, regulated, and integrated.
The unique complexity and organization of cellular metabolism reliably does not mean that any basic chemical or physical laws are broken within living systems; instead, it shows the complex interaction of these laws in a highly structured environment.
The distinct and highly regulated pattern of chemical changes in a living cell reliably shows the underlying biological organization and control mechanisms, such as compartmentalization (reactions happening in specific areas), enzyme regulation, and feedback loops.
Hormones
From a biochemical and physiological perspective, hormones can be functionally considered chemical messengers within an organism that send signals between cells and regulate various physiological processes.
Experts in the field reliably study hormones at three different and complementary levels of biological organization: their effects on tissues and organs (physiological), their chemical structure, and the exact way they act inside cells and at the molecular level.
Studying the overall physiological effects of hormones is confidently considered the main area of the scientific discipline known as physiology.
Initial investigations into how hormones function, such as studies involving removing organs and administering extracts, reliably had to be conducted before detailed chemical studies of hormone structure and mechanism could be effectively pursued to identify potential hormonal activity.
Based on extensive analytical chemical research, the precise chemical structures of the hormones thyroxine and adrenaline are reliably known.
Chemically speaking, the sex hormones and adrenal hormones are reliably classified as a specific type of organic compound based on lipids called steroids.
The detailed chemistry, including how they are made and broken down, of the sex and adrenal hormones has been subjected to extensive and thorough biochemical investigation.
Chemically, the hormones produced by the pancreas, like insulin and glucagon, and the pituitary gland (hypophysis), like growth hormone, are reliably identified as a general class of biological molecules: peptides or proteins.
Peptides are basically defined as chemical compounds consisting of two or more amino acids linked in a chain.
Using established techniques for determining protein sequences, the detailed chemical structures of most of these peptide hormones have reliably been determined.
Some well-known examples of plant hormones whose precise chemical structure has been reliably found include auxin, gibberellic acid, cytokinin, abscisic acid, and ethylene.
Within plant physiology, plant hormones such as auxin and gibberellic acid reliably play a fundamental role in regulating growth, development, and responses to environmental stimuli.
Based on extensive biochemical and physiological research, the first two stages of hormone investigation, focusing on physiological effects and chemical structure, have been explored very thoroughly and are largely finished for many hormones.
The extent to which the third stage of hormone research, investigating the precise chemical mechanisms by which hormones have effects inside cells, has been developed and fully understood varies greatly depending on the specific hormone, with some mechanisms being well-understood and others still being actively researched.
Based on current biochemical understanding, it is not reliably considered likely that all different hormones exert their effects through identical cellular and molecular mechanisms; instead, they use diverse signaling pathways.
Some of the distinct cellular and molecular mechanisms through which hormones have been reliably shown to have biological effects include attaching to receptors on the cell surface and activating signal transduction cascades, attaching to receptors inside the cell and changing gene expression, or acting as enzyme cofactors.
Genetics and Biochemistry
Genetic studies have definitively shown that specific biological molecules are responsible for maintaining and passing on a species’ hereditary characteristics: DNA (deoxyribonucleic acid).
Based on authoritative molecular biology, genes are primarily made of a specific type of large biological molecule: DNA.
Inside the structure of eukaryotic cells (cells with a nucleus), genes are reliably located in the specific cellular component known as the nucleus, organized on chromosomes.
Fundamental aspects concerning how genes work and act that were reliably clarified through groundbreaking research during the mid-20th century include that genes carry instructions for making proteins and that genetic information flows from DNA to RNA to protein.
Inside the nucleus, the DNA reliably directs the making of a crucial messenger molecule, mRNA (messenger RNA), through the process of transcription.
Among its various functions, RNA reliably guides the making of an essential class of large biological molecules, proteins, through the process of translation.
The specific structural feature of a protein molecule that reliably determines its ability to function as a catalytic enzyme is its unique three-dimensional shape (conformation), which creates a region (active site) for substrates to bind and be catalyzed.
The basic causal link between specific genes and the production of functional enzymes has been reliably shown through scientific experiments.
George Beadle and Edward Tatum are the specific scientists reliably credited with designing and successfully carrying out the groundbreaking experiments that first demonstrated the direct link between genes and enzymes, a concept formulated as the “one gene-one enzyme” hypothesis.
Beadle and Tatum used a specific simple organism in their key experiments showing the gene-enzyme relationship: the bread mold Neurospora crassa.
Through their experimental methods, Beadle and Tatum were reliably able to isolate and study specific types of the organism’s genetically altered strains called nutritional mutants.
The specific genetic change that had occurred in these strains, causing them to have different nutritional needs compared to the original organism, was a mutation in a single gene.
These mutant strains isolated by Beadle and Tatum reliably showed altered nutritional needs compared to the normal parent strain by being unable to produce a specific essential nutrient (e.g., an amino acid or vitamin) that the normal type could make.
Through subsequent biochemical analysis of these mutant strains, a specific enzyme activity essential for a metabolic pathway was reliably shown to be missing or not working.
The improvement of techniques for isolating mutants with specific nutritional deficiencies reliably made detailed investigations into fundamental biochemical systems, especially metabolic pathways, easier.
The start of space exploration in the mid-20th century significantly increased scientific questioning about the fundamental question concerning life’s origin and the possibility of life elsewhere.
Simultaneously with the beginning of space exploration, humankind was starting to reliably understand a basic biological process concerning inheriting traits: the molecular basis of heredity, specifically the role of DNA and the genetic code.
By comparing the exact biochemical structure of similar proteins across different species, insights into evolutionary relationships and history became reliably clear, making it possible to build evolutionary trees.
Some prominent examples of functional proteins whose amino acid sequences have been extensively and reliably compared across species to study evolutionary changes include cytochrome c, hemoglobin, and ribosomal RNA.
Phylogeny is defined as the study of the evolutionary history and relationships among organisms.
Given their focus on the molecular basis of life, biochemists naturally approached the fundamental scientific question about the origin of life on Earth from the viewpoint of chemical evolution, investigating how complex biological molecules could arise from simple inorganic precursors under conditions found on early Earth.
From the perspective of advanced biochemical science, the potential future creation of a living cell from nonliving components was seen as a challenging but possibly achievable long-term goal, requiring a complete understanding and control of cellular processes.
Applications of Biochemistry
An early and important goal in developing applied biochemistry was a specific and practical goal concerning analyzing blood components: the development of reliable methods for precisely measuring substances like glucose, urea, and electrolytes in blood.
The development of reliable analytical methods for blood components was an early objective in biochemistry for the crucial clinical purpose related to diagnosis and patient care: providing objective biochemical information to help in diagnosing diseases, predicting outcomes, and monitoring treatment effectiveness.
The clinical chemistry laboratory has reliably taken on an essential and authoritative role for doctors and hospitals in modern healthcare by providing vital diagnostic information from analyzing patient samples biochemically.
Some long-established biochemical methods for analyzing and diagnosing common diseases are still reliably and routinely used in clinical laboratories today, often in automated forms.
For the reliable diagnosis of diabetes, tests measuring specific components in blood are routinely used, primarily glucose and glycated hemoglobin (HbA1c).
For the reliable diagnosis or assessment of kidney disease, tests measuring specific components in blood are routinely used, primarily urea (blood urea nitrogen, BUN) and creatinine.
For the reliable diagnosis of gout, tests measuring a specific component in blood are routinely used, primarily uric acid.
For the reliable diagnosis or assessment of liver and gallbladder diseases, tests measuring specific components in blood are routinely used, primarily liver enzymes (e.g., ALT, AST, ALP), bilirubin, and albumin.
As biochemical knowledge about enzymes advanced, measuring a specific property related to enzymes in biological fluids has reliably become significantly valuable for diagnosis: their activity levels or specific variants (isoenzyme profiles).
Reliably measuring alkaline phosphatase levels in blood plasma provides valuable diagnostic information in specific diseases or conditions involving bone disorders, liver disease, and bile duct obstruction.
Reliably measuring acid phosphatase levels in blood plasma provides valuable diagnostic information in a specific disease: prostate cancer.
Reliably measuring amylase levels in blood plasma provides valuable diagnostic information in a specific medical condition: pancreatitis.
Reliably measuring lactate dehydrogenase and transaminase levels (ALT, AST) in blood plasma provides valuable diagnostic information in specific medical conditions involving tissue damage, such as heart attack, liver damage, and muscle injury.
Electrophoresis is routinely and reliably used for diagnosing specific abnormalities or changes in the composition of plasma proteins, such as abnormal proteins (paraproteins) in multiple myeloma or lack of specific antibody proteins (globulins).
Electrophoresis and ultracentrifugation of components in serum, especially lipoproteins, are increasingly and reliably used for assessing and diagnosing specific medical conditions related to disorders of fat metabolism and the risk of cardiovascular disease.
Automated machines have been developed extensively for simultaneously analyzing many blood components to improve efficiency, speed, and reliability in clinical diagnostics, allowing for fast and cost-effective testing of large numbers of samples.
Reliable biochemical methods have been effectively applied within the food industry in specific practical ways, including controlling quality, ensuring food safety, analyzing nutritional content, and monitoring processing steps.
Biochemical research efforts within the food industry are particularly focused on improving specific aspects related to food quality, safety, and processing, such as preventing spoilage, making nutritional value better, and optimizing fermentation processes.
Specific biochemical processes can cause desirable qualities like vitamins, color, and taste to degrade in preserved food products, including reaction with oxygen (oxidation), breakdown by enzymes, and browning not caused by enzymes (Maillard reaction).
In the context of processing food, tests for enzyme activity are reliably used for specific purposes in quality control or process monitoring, such as checking if pasteurization was done correctly (e.g., phosphatase test) or tracking how fermentation is progressing.
Biochemical techniques have reliably played an essential and widely recognized role in the complex process of developing new pharmaceutical drugs by providing tools to identify drug targets, screen potential compounds, and study how drugs are processed by the body and how they act.
Specific types of biological assays and biochemical evaluations routinely included in testing potentially useful drug compounds include tests for inhibiting enzymes, tests for binding to receptors, and cell-based tests measuring cellular responses.
Such studies aimed at reliably testing potential drugs heavily depend on the availability and application of fundamental scientific tools and knowledge derived from biochemistry, cell biology, and molecular biology.
Many commonly used pharmaceutical drugs have been developed through historical approaches involving testing large collections of compounds for desired biological activity and chemically changing existing drugs to make them work better or have fewer side effects.
An increasing number of modern therapeutic agents are being designed intentionally based on detailed biochemical understanding of how diseases work and what specific molecular targets are involved, allowing for the creation of highly specific drugs that interact with particular proteins or pathways.
Recent and ongoing advancements in biochemistry, such as techniques to study structure (structural biology), rapid large-scale screening, and analyzing genomes/proteomes, hold significant promise for further assisting in creating highly specific and effective pharmaceuticals.
Biochemical Techniques
Similar to other established scientific fields, biochemistry constantly aims to achieve a basic goal through its investigations: the quantitative understanding and precise measurement of the chemical components and processes in living systems.
Biochemistry reliably achieves precise measurements of biological substances and processes using specific analytical techniques and methods, such as using light absorbance (spectrophotometry), separating components (chromatography, electrophoresis), measuring mass (mass spectrometry), and various tests involving enzymes (enzymatic assays).
The earliest method used for studying the chemical events happening inside a living organism was a simple yet basic approach: analyzing the chemical composition of substances going into and coming out of the organism.
Analyzing materials entering and leaving is still the basic principle for a specific type of nutritional or metabolic experiments conducted on animals called balance experiments.
For the purpose of reliably conducting balance experiments, specific types of quantitative chemical analytical methods have been developed and improved, including measuring weight (gravimetric analysis), using titration (titrimetry), and using spectrophotometry.
For accurate quantitative measurements when using color-based chemical methods, a specific laboratory instrument is needed: a spectrophotometer or calorimeter.
Specific analytical techniques that are routinely used for reliably measuring how much oxygen is consumed and how much carbon dioxide is produced in biological systems include using gas measurements (gasometry) or measuring respiration (respirometry).
A specific and informative metabolic ratio reliably calculated from these gas measurements of oxygen uptake and carbon dioxide release is the respiratory quotient (RQ).
The respiratory quotient is defined as a metabolic indicator derived from gas measurements, calculated as the ratio of the volume of carbon dioxide produced to the volume of oxygen consumed over a given period.
Beyond studying whole organisms in balance experiments, a refined experimental approach involving isolated systems has allowed for getting more detailed biochemical information: studying biological materials in vitro (in glass/in the lab), such as cell extracts, separated organelles, or purified enzymes.
To enable detailed biochemical analysis of specific functions, it became essential to physically break apart cellular structure through homogenization and separate individual cellular components using techniques like centrifugation.
Some key examples of specific cellular organelles or components that are routinely separated for detailed biochemical investigation include mitochondria, nuclei, ribosomes, lysosomes, and plasma membranes.
A crucial laboratory instrument that is widely used in biochemical research for reliably separating cellular components or molecules based on their size or density is a centrifuge.
By applying centrifugal force, a centrifuge reliably causes the separation of substances within a mixture based on their differing densities or sedimentation rates, with denser or larger particles moving outward faster.
Some examples of specific cellular components or biological particles that can be reliably separated from complex mixtures using centrifugation techniques include cell nuclei, mitochondria, ribosomes, and even large protein complexes or viruses.
By using very high-speed spinning, such as in ultracentrifugation, individual proteins are reliably separated from each other based on their differences in mass and shape.
Using ultracentrifugation combined with specialized optical systems, a specific physical property of proteins that can be reliably determined is their sedimentation coefficient, which relates to their molecular weight and shape.
Besides molecular mass or weight, electrical charge is another basic chemical property of biological molecules that has been widely and effectively used for separating and analyzing them.
A specific chemical factor that reliably determines whether amino acids and proteins carry a net positive, negative, or neutral electrical charge is the pH of the surrounding solution relative to their isoelectric point (pI).
Based on their electrical charge, molecules predictably move when exposed to an electric field, thus allowing their separation through electrophoresis, where positively charged molecules move towards the negative electrode and negatively charged ones towards the positive.
Electrophoretic separations of charged biological molecules can be reliably performed in types of porous solid or gel materials such as polyacrylamide gel or agarose gel.
After separating proteins using electrophoresis, the individual proteins in a mixture can be reliably detected, seen, and measured precisely using methods such as staining with dyes (e.g., Coomassie blue), using radioactive labels (autoradiography), or using antibodies (Western blotting).
In addition to analyzing quantity, a crucial step in protein purification that can be reliably achieved for separated proteins using preparative electrophoresis is the physical isolation and collection of the protein bands or spots.
A significant structural difference in human hemoglobin, which is linked to a specific genetic disease (sickle-cell anemia), was reliably identified through using electrophoresis in the 1950s.
Based on biochemical and genetic studies, sickle-cell anemia stands as the first definitive and reliable example proving a basic biological idea: that a change in a single gene can cause a change in a specific protein structure, leading to a human genetic disease.
Another basis for analytical separation techniques is a basic chemical principle involving different distribution between phases, often related to how well a substance dissolves in different solvents, which is known as partition or chromatography.
In its early historical use, separation based on the principle of partition was reliably carried out using liquid phases, such as separating substances between two liquids that don’t mix.
A specific and very effective simplified separation technique, using different solubility and adsorption on a paper material, that developed from the principle of partition is paper chromatography.
Using paper chromatography, chemical substances in a mixture could be reliably separated based on how differently they moved along the paper as a solvent flowed through it, and then identified based on where they stopped or how they reacted to color tests.
Unlike electrophoresis, which mainly separates charged molecules, paper chromatography has been reliably used to separate types of biological substances including amino acids, sugars, and pigments.
The reliable technique of paper chromatography has significantly helped in analyzing and understanding complex mixtures in biochemical research by providing a simple, inexpensive, and effective method for separating and identifying components of biological extracts.
Starting from simple filter paper strips, the basic principle of chromatography has been extended to more advanced separation formats, such as column chromatography, thin-layer chromatography (TLC), and gas chromatography (GC).
Compared to paper methods, column chromatography reliably allows for increased capabilities and flexibility for separating substances, including larger sample sizes, using different stationary phases, and continuous elution.
A particularly significant and complex mixture of biological molecules that was successfully and reliably separated using chromatography on columns containing ion-exchange resins was a mixture of amino acids, which led to the precise determination of protein composition.
The reliable separation of amino acids using ion-exchange chromatography makes it possible to determine crucial information about proteins: their amino acid composition.
After a protein’s amino acid composition is reliably determined, specific aspects of its detailed structure that can be explained using other organic chemistry techniques include the sequence of amino acids and the location of disulfide bonds.
The reliable separation achieved by chromatography in columns that separates based on size (size exclusion chromatography) is primarily based on a physical property of molecules: their size or hydrodynamic volume.
In size exclusion column chromatography, larger molecules reliably move through the column material faster compared to smaller molecules because they are kept out of the pores of the stationary phase and travel a shorter path.
In addition to separating molecules by size, size exclusion chromatography reliably allows for estimating another valuable piece of information about biological molecules: their approximate molecular weight.
Arguably the single most significant tool in dissecting the complexities of metabolic pathways, known for its power and reliability in tracking molecular transformations, has been the biochemical technique using isotopes as tracers.
In this crucial technique for studying metabolism, stable or radioactive isotopes are reliably used to track the fate of specific atoms or molecules through biochemical pathways by incorporating them into starting substances and following their movement and changes within the living system.
For accurately and reliably measuring compounds labeled with isotopes in biological samples, specific detection technologies have been necessary to develop and use, such as Geiger counters, scintillation counters, and mass spectrometers.
Some key examples of other sophisticated physical techniques that have become essential and powerful tools in modern biochemical research include Nuclear Magnetic Resonance (NMR) spectroscopy, X-ray crystallography, cryo-electron microscopy, and mass spectrometry.
These advanced physical techniques like NMR and X-ray crystallography reliably help to reveal detailed information about the three-dimensional shape, movement, and interactions of biological molecules, providing insights into how they function at the atomic level.
Here is a summary of some key historical milestones in biochemistry:
| Year / Period | Key Discovery / Event | Scientists Involved | Significance |
|---|---|---|---|
| Late 18th Century | Respiration as slow combustion; Photosynthesis as reciprocal process | Lavoisier, Priestley, Ingenhousz, Senebier | Foundation of bioenergetics and elemental cycles. |
| 1828 | Synthesis of Urea from inorganic precursors | Friedrich Wöhler | Challenge to vitalism; bridge between organic and inorganic chemistry. |
| Mid-19th Century | Application of chemistry to agriculture; Microbial fermentation (early work) | Justus von Liebig, Louis Pasteur | Establishment of applied biochemistry; understanding of biological agents. |
| Late 19th Century | Identification of “ferments” as enzymes; Isolation of nuclein | Various, Eduard Buchner, Friedrich Miescher | Beginning of enzymology; discovery of nucleic acids. |
| 1920s | Vitamin mechanisms; Crystallization of the first enzyme (Urease) | Various, James B. Sumner | Understanding of essential nutrients; confirmation of enzyme protein nature. |
| 1929 | Isolation of ATP | Karl Lohmann | Discovery of key energy currency. |
| 1930s | Use of isotopes as tracers; Localization of metabolic pathways in cells | George de Hevesy, Various | Powerful tools for studying metabolism and cell function. |
| 1941 | ATP proposed as universal energy currency | F.A. Lipmann | Unifying concept in cellular energy metabolism. |
| 1944 | DNA as genetic material (Avery-MacLeod-McCarty experiment) | Oswald Avery, Colin MacLeod, Maclyn McCarty | Revolution in genetics; focus shifts to molecular level. |
| 1950s | Amino acid sequencing of insulin; Double helix structure of DNA; Hemoglobin structure | Frederick Sanger, Watson, Crick, Wilkins, Perutz | Understanding protein sequence; Elucidation of DNA structure. |
| 1960s-Present | Elucidation of genetic code, metabolic pathways; Development of recombinant DNA; NMR, X-ray crystallography applications | Various | Rapid advancement in molecular biology, structural biology, and metabolism. |
This comprehensive overview shows how biochemistry has evolved from studying the chemistry of life substances to becoming a sophisticated field that explains life’s processes at the molecular level, using a wide variety of analytical techniques and contributing significantly to many applied areas.
