15 julio, 2024

Biomolecules: what they are, definition, types, functions

What are biomolecules?

The biomolecules or biological molecules They are the chemical compounds with which living beings are formed, that is: human beings, animals, plants, fungi, bacteria, parasites, etc.

Like all chemical compounds, biomolecules are made up of atoms of different elements, but mainly from the group consisting of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P ) and sulfur (S). Many times these are known as bioelements.

Biomolecules are fundamental for the existence of living beings, since they are considered the small blocks with which cells are built, which are the basic units of life.

All cells, in addition to being made up of biomolecules, need them to feed and nourish themselves, to reproduce and move, and to interact with the environment that surrounds them.

In nature there are many different types of biomolecules, but among all of them there are four that are particularly important: nucleic acids, proteins, carbohydrates and lipids, which are also known as macromolecules; we will see immediately why its importance is due.

Functions of biomolecules

Biomolecules are so important for living beings that it is sometimes difficult to summarize what are the specific functions they fulfill, however, we can highlight the following:

They store, multiply and transmit the information that contains the instructions necessary to manufacture other biomolecules, as well as for a cell to reproduce, feed itself and regulate its internal processes.
They are the structural components that give support, shape and movement to all the types of cells that exist in nature and that form the living beings that we know.
They function as sources of energy that cells use to carry out their tasks and even represent energy reserves that can only be used when needed.
They participate in intracellular and intercellular communication, either as messages, as receiving sites, or as message multipliers.

Classification of biomolecules (types)

According to their chemical characteristics, different authors make the distinction between two main types of biomolecules:

organic biomolecules.
inorganic biomolecules.

Although organic biomolecules are among the most abundant and important, living beings need both types of biomolecules to be what they are and to survive.

organic biomolecules

Organic biomolecules are those that are composed mainly of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), and sulfur (S), which are combined with much smaller amounts of other elements. such as calcium (Ca), sodium (Na), potassium (K), magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), among others.

Most of these biomolecules are known as macromolecules, since they are made up of hundreds of thousands of atoms of these bioelements.

Their functions are highly diverse, but in general they have an important role from the structural, energetic, and storage and transmission of information between a cell and its offspring.

The following four groups of organic biomolecules are recognized:

Lipids are the main molecules that exist in the membrane that surrounds cells, and in eukaryotic cells, intracellular organelles. These are molecules that «flee» from water -they are hydrophobic- and that, in an aqueous environment, associate with each other so that only their less hydrophobic parts are exposed to the water.

Lipids are mainly made up of carbon, hydrogen and oxygen atoms, and these are also important sources of energy for cells, which are capable of obtaining it through oxidation.

The main types of lipids are phospholipids -those that form cell membranes-, but there are also others: fats, waxes, sterols and triglycerides, to name a few. In other words, the oil we use for cooking is made up of lipids, just like the membranes of each of our cells.

Carbohydrates or carbohydrates

Carbohydrates, also known as carbohydrates, saccharides or sugars, are another group of organic biomolecules essential for cell life; They are among the most abundant macromolecules on our planet.

Like lipids, these biomolecules are essentially made up of carbon, hydrogen, and oxygen.

Not only do we consume them every day and are used by our cells for energy and communication, but they are also the structural components of the tissues of many different organisms.

Plants, for example, use cellulose, a glucose polymer, to build their cell walls and thus their entire bodies. Fungi do the same, but with another sugar polymer known as chitin, which is also used by insects to coat their bodies.

The carbohydrates with which we are most familiar are those that we eat daily: table sugar and starch, lactose from milk, cheese and yogurt, etc.

Depending on the number of sugars they are composed of, carbohydrates can be: monosaccharides (1 sugar), disaccharides (2 sugars), oligosaccharides (more than 3 sugars) and polysaccharides (a large number of sugars, all the same or different).

Amino acids and proteins

Proteins represent another important group of organic biomolecules. They are actually amino acid polymers, which means they are made up of hundreds of amino acids linked together.

Proteins, and therefore amino acids, are mainly made up of carbon, hydrogen, oxygen and nitrogen atoms, but they can also be associated with other atoms such as phosphorus, sulfur, iron, magnesium, nickel, zinc and others. .

Our cells can produce a large number of amino acids on their own, but there are others that we must obtain from the food we eat daily, whether of animal or vegetable origin.

Proteins represent about 50% of the dry weight of cells and are the little «machines» that carry out all cellular functions and, as if that were not enough, they also have structural functions.

Those proteins that function as «machines» are known as enzymes; these and proteins with structural functions are produced from the information contained in nucleic acids.

Nucleotides and nucleic acids

Nucleic acids (deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)) are informational biomolecules found in the nucleus of eukaryotic cells or in the cytoplasm of prokaryotic cells. They are polymers of other smaller molecules known as nucleotides.

Nucleic acids are made up of carbon, nitrogen, hydrogen, phosphorus, and oxygen atoms. The sequence or the order in which the nucleotides of each nucleic acid are arranged with respect to the others contains very important information for cells.

Proteins are formed thanks to the reading of the nucleotide sequence in the DNA and its transcription into RNA, which is then translated in the form of amino acids ordered very specially in the protein sequence.

When a cell divides, it duplicates all this information and passes a copy to the daughter cell, allowing the latter to produce proteins and thus carry out all the normal processes of any cell.

inorganic biomolecules

Inorganic biomolecules are not formed by combinations between carbon, hydrogen and oxygen, as organic ones are. Instead, it is often about smaller molecules, individual atoms, even that perform very specific functions in living beings.

Water is, par excellence, the universal solvent. The body of a human being is made up of more than 50% of this liquid and this is necessary for the cells to carry out all the tasks that characterize them.

A water molecule is made up of three atoms: two hydrogen and one oxygen. The physical and chemical properties of these molecules mean that the liquid they make up fulfills multiple purposes in nature.

Oxygen, carbon dioxide, and nitrogen are good examples of inorganic biomolecules essential to living things. These gases tend to enter and leave cells constantly and many are used as substrates to carry out different metabolic functions.

Ions: anions and cations

Other inorganic biomolecules are very small or are atoms of negatively or positively charged elements such as chlorides, phosphates, carbonates, sodium, potassium, ammonium, calcium, magnesium, and others.

Despite their small size, these biomolecules are essential for many chemical reactions that occur inside cells.

Its transport from one side of cell membranes to the other is important for the establishment of certain internal cellular conditions, since its concentrations inside and outside cells can be highly variable.

References

Alberts, B., Bray, D., Hopkin, K., Johnson, AD, Lewis, J., Raff, M., … & Walter, P. (2015). Essential cell biology. Garland science.
Chang, R. (2008). General chemistry: the essential concepts. Boston: McGraw-Hill.
Macarulla, JM, & Goñi, FM (1993). Biomolecules: lessons in structural biochemistry. I reversed.
Nelson, DL, Lehninger, AL, & Cox, MM (2008). Lehninger principles of biochemistry. macmillan.
Solomon, E.P., Berg, L.R., & Martin, D.W. (2011). Biology (9th edn). Brooks/Cole, Cengage Learning: USA.

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