Biomolecules or biological molecules are all molecules inherent to living beings, either as a product of their biological functions or as constituents of their bodies. Think of them as the essential ingredients and tiny machines that keep life going. Biomolecules are essential in the formation and functioning of living beings, from the simplest microorganisms to humans. Indeed, biomolecules are essential for the birth, development, and functioning of all cells that make up living organisms.
Where do they come from? Well, many are made right inside us! Organic biomolecules are the product of the body’s own chemical reactions. And biomolecules are those that are produced within the organism or cells. This is why biomolecules can be endogenous or exogenous. Endogenous means that the biomolecule is produced within a living organism. Others, we get from our food. The processes involved in nutrition allow living beings to obtain biomolecules in order to synthesize their own.
These aren’t just simple particles; they come in an enormous and varied range of sizes, shapes, and functions. Most often, most biomolecules can be considered to derive from the simplest class of organic molecules, hydrocarbons. And what are these hydrocarbons made of? Primarily, the four elements are oxygen, hydrogen, carbon, and nitrogen. It’s how these elements arrange themselves that gives biomolecules their special powers. The chemical properties of the molecules constructed in this way are determined by certain specific sets of atoms, called functional groups. These molecules are more water-soluble than long carbon chains, but more hydrophobic than an alcohol.
There’s a beautiful organizing principle here: biomolecules share a fundamental relationship between structure and function, which also involves the environment in which they are found. This idea is so central that, as D. Green & R. Goldberger noted, “The fundamental concept of biochemical universals (properties, systems, and principles that are applicable to all life forms) provides the framework for a logical and predictive science of life, based on the cell principle.” It’s not just about listing parts; in fact, Biochemistry not only studies biomolecules but also the relationships established between their components, their transformations in living beings, and the regulation of these processes. It’s a dynamic, interconnected world. And these aren’t just abstract chemicals; they form tangible things too. For instance, biological materials: are those generated by nature itself, such as wood or human bones.
So, What are the Main Types of Biomolecules?
You might hear slightly different lists, but generally, scientists focus on a core group. The four main biomolecules are carbohydrates, lipids, proteins, and nucleic acids. Sometimes, you’ll see a slightly expanded list: The five main biomolecules are: carbohydrates, proteins, lipids, nucleic acids, and vitamins. And to be even more comprehensive: The main biomolecules are carbohydrates, proteins, lipids, amino acids, vitamins, and nucleic acids (though amino acids are the building blocks of proteins).
No matter how you categorize them, biomolecules such as carbohydrates, lipids, proteins, and nucleic acids shape all living organisms. Each of these molecules plays a very important role in the structure and metabolism of animals and plants. For this reason, it is essential to understand their general characteristics. Let’s take a closer look at each of these superstars.
1. Carbohydrates: More Than Just Sugar Rush!
When you think carbs, you probably think bread, pasta, or sugary treats, right? And you’re not wrong! Carbohydrates are compounds containing carbon, hydrogen, and oxygen in the ratios 6:12:6 – a classic example being glucose. More generally, the name carbohydrate literally means carbohydrates and comes from their chemical composition, which for many of them is (C·H2O)n, where n ≥3.
- Energy Powerhouses: Their primary role? Energy! Glucose, or blood sugar, is the main source of energy for the body’s cells, tissues, and organs. And it’s not just humans; for many organisms, carbohydrates generally make up the largest portion of their diet, as much as 80 percent in some cases. Our bodies are smart about storing this energy too. Carbohydrates are a source of energy in the form of glycogen, which is quickly mobilized to generate glucose when needed.
- Types of Carbs: They aren’t all the same. There are four types, depending on their chemical structure: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Let’s break that down:
Monosaccharides are the simplest sugars and constitute the basic structural unit of carbohydrates. Yes, the simplest carbohydrates are monosaccharides or simple sugars. Examples include glucose, fructose, and galactose.
Link two monosaccharides, and you get disaccharides like sucrose (your table sugar!), lactose, and maltose.
Traditionally, the combination of 3 to 10 monosaccharide units is called oligosaccharides.
And when many link up? Polysaccharides are complex carbohydrates made up of a large number of simple sugars, which are linked together by glycosidic bonds. Think starch, glycogen (often called animal starch), and cellulose.
Interestingly, some complex carbs aren’t for energy, at least not for us. Cellulose, hemicellulose, lignin, pectin, and gums are sometimes referred to as unavailable carbohydrates because humans cannot digest them – they’re what we call fiber!
So, broadly, carbohydrates can be divided into three groups: monosaccharides, e.g., glucose, fructose, galactose; disaccharides, e.g., sucrose (table sugar), lactose, maltose; and polysaccharides, e.g., starch, glycogen (animal starch), and cellulose.
- Building Blocks: Carbohydrates (sugars) -> Monosaccharides -> C, H, O.
2. Lipids: Fats, Oils, and So Much More
Lipids often get a bad rap (hello, “fat-free” craze!), but they are absolutely vital. What are they? Lipids are hydrophobic molecules (insoluble in water), but they are soluble in nonpolar organic solvents, such as benzene, benzine, and chloroform. This “water-fearing” nature is key to their function. Interestingly, as mentioned, lipids are molecules of an amphipathic nature. Water is a very polar molecule that easily forms bonds. This means many lipids have a part that dislikes water and a part that’s okay with it. In fact, they exhibit amphipathic behavior, with one polar and one nonpolar region; this property allows them to form membranes. Unlike other biomolecules, lipids are neither monomers nor polymers.
Key Functions:
- Energy Storage: The main function of lipids is as an energy store. And it’s a very efficient one!
- Cell Structure: In cells, lipids have three basic functions: as structural components of biological membranes, as energy stores, and as signaling molecules, that is, as carriers of information.
- Nutrient Absorption & More: Like carbohydrates, fats provide energy and help absorb certain nutrients. Lipids are neither monomers nor polymers. So, it’s not just about storage; these molecules have diverse functions, such as energy storage, chemical messengers, and they form parts of cell membranes.
- The Amazing Cell Membrane: One of the coolest roles of lipids is forming cell membranes. The lipid bilayer is a fundamental structure of cell membranes, formed by two layers of lipid molecules. This bilayer is primarily made of specific lipids: The lipid bilayer is composed primarily of phospholipids, which have a hydrophilic region (polar head) and a hydrophobic region (nonpolar tails). It’s this structure that makes membranes work. The chemical composition of membranes gives them essential properties for the functions they perform in the cell. And it’s not just lipids; note that many integral proteins and lipid molecules are covalently linked to carbohydrates (forming glycolipids and glycoproteins) within these membranes.
Examples of Lipids:
The most common dietary fats are fats or oils (also called triglycerides or triacylglycerides).
You find them everywhere! They are present in vegetable oils (olive, corn, sunflower, peanut, etc.), which are rich in unsaturated fatty acids, and in animal fats (bacon, butter, lard, etc.), which are rich in saturated fatty acids.
Other examples include:
- Vegetable oils
- Animal fats
- Fruit waxes
- Beeswax
- Found in Vegetables
Building Blocks: Lipids (fats, oils, and waxes) -> Fatty acids, glycerol -> C, H, O.
3. Proteins: The Cellular Workhorses
If cells were a bustling city, proteins would be the workers doing almost everything! They perform most of the work in cells and are necessary for the structure, function, and regulation of the body’s tissues and organs. It’s hard to overstate their importance; they perform vital functions of support, regulation of processes, and transport of substances in each of the cells that make up tissues, organs, and organ systems.
What are Proteins Made Of?
Proteins are formed by the polymerization of L-α-amino acids, linked by peptide bonds. Think of amino acids as beads on a string. There are 20 different amino acids. A protein has two or more chains of amino acids (called polypeptides) whose sequence is encoded in a gene. Even the union of a small number of amino acids gives rise to a peptide. What do these amino acids look like? Common amino acids have a similar general structure, consisting of a central carbon atom or alpha carbon atom (α), covalently bonded to an acid or carboxylic group (-COOH), a basic or amino group (-NH2), and a hydrogen atom. The “R” group is what makes each of the 20 amino acids unique.
Structure is Everything: The order of these amino acids is crucial. Primary structure, which corresponds to the sequence of amino acids linked in a row, is just the beginning. The amino acid sequence determines each protein’s unique three-dimensional structure and its specific function. This 3D shape is what allows proteins to do their specific jobs.
A Few Protein Roles (among many!):
- Transport: These proteins bind and transport atoms and small molecules within cells and throughout the body. Hemoglobin carrying oxygen is a classic example.
- Movement: You wouldn’t be able to move without muscle contractile proteins. For instance, tropomyosin is a vitally important protein in the human body, playing a key role in muscle function.
- Enzymes: Catalyzing biochemical reactions.
- Structural support: Like collagen in your skin.
How Much Protein Are We Talking?
Quite a bit! In an adult’s body, 18 to 19% of its weight is made up of proteins, which in a person weighing about 70 kg is approximately 13 kg.
Building Blocks: Proteins -> Amino acids -> C, H, O, N, S. (Note the addition of Nitrogen and sometimes Sulfur!)
4. Nucleic Acids: The Information Keepers
Last, but certainly not least, we have the molecules that hold the blueprint of life: nucleic acids. Nucleic acids are large biomolecules that perform essential functions in all cells and viruses. Indeed, nucleic acids are present in all cells and are responsible for storing, transmitting, and expressing genetic information. Their primary job? An important function of nucleic acids involves the storage and expression of genomic information.
The Dynamic Duo: DNA and RNA
The main types of nucleic acids are deoxyribonucleic acid (better known as DNA) and ribonucleic acid (RNA). You’ve definitely heard of them! Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the nucleic acids that function in the cell, store information, and form the basis of our genome.
DNA: The Master Blueprint
DNA has the function of “storing information.” That is, it contains the instructions that determine the shape and characteristics of an organism and its functions.
What does it look like? A DNA molecule is composed of two complementary strands that coil around each other and resemble a spiral staircase shaped like a helix. This iconic shape is key. The structure of the double helix is somewhat similar to a ladder: the base pairs form the rungs of the ladder, and the sugar and phosphate molecules are its handrails.
The building blocks of this ladder are called nucleotides. In DNA, each nucleotide is composed of three parts: a 5-carbon sugar called deoxyribose, a phosphate group, and a nitrogenous base.
DNA contains four nucleotides or bases: adenine (A), cytosine (C), guanine (G), and thymine (T).
These bases pair up in a specific way: Nucleotides are joined together (A to T and G to C) by chemical bonds and form base pairs that connect the two DNA strands.
Nucleotides: The Monomers
The monomeric units of nucleic acids are nucleotides, which are distinguished by the nitrogenous base they comprise.
More generally, a nucleotide consists of a sugar molecule (either ribose in RNA or deoxyribose in DNA) attached to a phosphate group and a nitrogenous base.
To be very specific: A nucleotide is made up of a nitrogenous base (adenine, guanine, thymine, or cytosine in DNA; adenine, guanine, uracil, or cytosine in RNA), a phosphate group, and a sugar molecule (deoxyribose in DNA; ribose in RNA). DNA and RNA are polymers composed of many nucleotides.
You might have noticed a new base: Uracil. Uracil is a nucleotide, like adenine, guanine, thymine, and cytosine, which are the building blocks of DNA, except that uracil replaces thymine in RNA.
So, in short, nucleic acids are composed of nucleotides abbreviated as A, C, G, T, and U.
From Code to Protein: How does this information get used? The genetic code refers to the instructions contained in a gene that tell a cell how to produce a specific protein. This complex process, turning DNA information into a functional protein, it consists of two main steps: transcription and translation.
Packing It All In: DNA molecules are incredibly long! For example, if all the DNA molecules in a single human cell were unwound from their histones and stretched end to end, they would measure 1.8 meters (6 feet). How does that fit? In order to fit their genomes into a cell, eukaryotes must pack their DNA firmly within the nucleus. The structure of the double helix is somewhat similar to a ladder: the base pairs form the rungs of the ladder, and the sugar and phosphate molecules are its handrails. It’s an amazing feat of engineering that all this DNA (along with a large amount of proteins) is contained in a small nucleus that measures 5 micrometers in diameter on average. The ladder analogy is popular for a reason: the structure of the double helix is somewhat similar to a ladder; the base pairs form the rungs of the ladder, and the sugar and phosphate molecules are its handrails.
Decoding the Code: Scientists can read this genetic information. DNA sequencing is the process of determining the sequence of nucleotide bases (As, Ts, Cs, and Gs) in a DNA fragment.
Building Blocks: Nucleic acids -> Nucleotides -> C, H, O, N, P. (Phosphorus is a key player here!)
A World of Organic Molecules
These four (or five, if you include vitamins separately!) are the headliners, but they represent a vast category of examples of organic molecules that are vital for life. Each plays an indispensable role, often working together in intricate ways.
Summary: The Essentials of Life
So, there you have it – a whirlwind tour of the major biomolecules!
- Carbohydrates: Our primary energy source, also involved in structure.
- Lipids: Fantastic for long-term energy storage, crucial for cell membranes and signaling.
- Proteins: The versatile workhorses, involved in almost every cellular process, from structure and transport to catalyzing reactions.
- Nucleic Acids (DNA & RNA): The keepers and interpreters of our genetic information, directing the synthesis of proteins.
These amazing molecules are truly the essence of what makes us, and all life, tick. They are the foundation upon which the complex structures and functions of living organisms are built. Next time you eat a meal or just marvel at the world around you, remember the incredible biomolecules at work!
