What are Proteins, their Types & Structures?

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What are Proteins, their Types & Structures?

What are Proteins

What are Proteins, their Types & Structures?

Proteins are a macronutrients that are vital to building muscle mass. They are generally found in animal products. However, they are also present in other sources, such as nuts and legumes.

There are three macronutrients: protein, fats and carbohydrates. Macronutrients provide calories, or energy. The body necessitates large amounts of macronutrients to sustain life, hence the term “macro,” according to the University of Illinois McKinley Health Center. One gram of protein contains 4 calories. Protein makes up about 15 percent of a person’s body weight.

Chemically, protein is composed of amino acids, which are organic compounds composed of carbon, hydrogen, nitrogen, oxygen or sulfur. Amino acids are the building blocks of proteins, and proteins are the building blocks of muscle mass.

Read Also: Vitamins – Types, Sources & Functions

Important Types

Proteins can play a vital role in a cell or organism. Here, we’ll share some important types of proteins.


Enzymes act as catalysts in biochemical reactions they speed the reactions up. Each enzyme distinguishes one or more substrates, the molecules that serve as starting material for the reaction it catalyzes.

Read More: What are Enzymes, their Types & Functions?


Hormones are long-distance chemical signals released by endocrine cells. They control specific physiological processes, such as growth, improvement, metabolism, and reproduction. While some hormones are steroid, others are proteins. These protein-based hormones are generally called peptide hormones.

Amino Acids

Protein consists of amino acids, and amino acids are the building blocks of protein. There are around 20 amino acids.

These 20 amino acids can be arranged in millions of different ways to create millions of different proteins, each with a particular function in the body. The structures differ according to the order in which the amino acids combine.

The 20 different amino acids that the body practices to synthesize proteins are: Alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.

Structures of Proteins

Primary structure

Analytical and synthetic procedures disclose only the primary structure of the proteins—that is, the amino acid sequence of the peptide chains. They do not reveal information about the conformation of the peptide chain. That is, whether the peptide chain is existing as a long straight thread or is irregularly coiled and folded into a globule.

Secondary structure

The nitrogen and carbon atoms of a peptide chain cannot lie on a conventional line, because of the magnitude of the bond angles between nearby atoms of the chain; the bond angle is about 110°. Each of the nitrogen and carbon atoms can rotate to a specific extent, however, so that the chain has a limited flexibility. Because all of the amino acids, except glycine, are asymmetric L-amino acids, the peptide chain tends to adopt an asymmetric helical shape. Some of the fibrous proteins consist of elongated helices around a straight screw axis.

Tertiary structure

The tertiary structure is the product of the collaboration between the side chains (R) of the amino acids composing the protein. Some of them contain positively or negatively charged groups, others are polar, and still others are nonpolar. The number of carbon atoms in the side chain fluctuates from zero in glycine to nine in tryptophan. Positively and negatively charged side chains have the tendency to fascinate each other; side chains with identical charges repel each other.

Quaternary structure

The nature of the quaternary structure is established by the structure of hemoglobin. Each molecule of human hemoglobin contains four peptide chains, two α-chains and two β-chains; i.e., it is a tetramer. The four subparts are linked to each other by hydrogen bonds and hydrophobic interaction. Because the four subparts are so closely linked, the hemoglobin tetramer is called a molecule. Even though no covalent bonds ensue between the peptide chains of the four subunits.

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