Applications of Proteins in Daily Life

Proteins are large complex molecules that are made up of hundreds or thousands of smaller units of amino acids which are attached forming long chains. The sequence of these amino acids determines each protein’s unique 3-dimensional structure and its specific function. Amino acids are coded by combinations of three DNA building blocks which are nucleotides.

They are large biomolecules and macromolecules that perform a vast array of functions within organisms, including catalyzing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another.

Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity.

Most microorganisms and plants can biosynthesize all 20 standard amino acids, while animals (including humans) must obtain some of the amino acids from the diet. The amino acids that an organism cannot synthesize on its own are referred to as essential amino acids.

Key enzymes that synthesize certain amino acids are not present in animals—such as aspartokinase, which catalyzes the first step in the synthesis of lysine, methionine, and threonine from aspartate. If amino acids are present in the environment, microorganisms can conserve energy by taking up the amino acids from their surroundings and down-regulating their biosynthetic pathways.

In animals, proteins are obtained through the consumption of foods containing protein. Ingested proteins are then broken down into amino acids through digestion which typically denatures the proteins through exposure to acid and hydrolysis by enzymes called proteases.

Some ingested amino acids are used for protein biosynthesis, while others are converted to glucose through gluconeogenesis, or fed into the citric acid cycle. This use of protein as a fuel is particularly important under starvation conditions as it allows the body’s proteins to be used to support life, particularly those found in muscle.

You can also look at what is the importance of proteins in body.

Formation And Synthesis of Proteins

The process of synthesizing a protein from an mRNA template is known as translation. The mRNA is loaded onto the ribosome and is read three nucleotides at a time by matching each codon to its base pairing anti-codon located on a transfer RNA molecule, which carries the amino acid corresponding to the codon it recognizes.

The enzyme aminoacyl tRNA synthetase “charges” the tRNA molecules with the correct amino acids. The growing polypeptide is often termed the nascent chain. Proteins are always biosynthesized from N-terminus to C-terminus. The size of a synthesized protein can be measured by the number of amino acids it contains and by its total molecular mass, which is normally reported in units of daltons.

Short proteins can also be synthesized chemically by a family of methods known as peptide synthesis, which rely on organic synthesis techniques such as chemical ligation to produce peptides in high yield. Chemical synthesis allows for the introduction of non-natural amino acids into polypeptide chains, such as the attachment of fluorescent probes to amino acid side chains.

These methods are useful in laboratory biochemistry and cell biology, though generally not for commercial applications. Chemical synthesis is inefficient for polypeptides longer than about 300 amino acids, and the synthesized proteins may not readily assume their native tertiary structure. Most chemical synthesis methods proceed from C-terminus to N-terminus, opposite the biological reaction.

Types of Protein and Structure of Protein

Depending upon the external combination, proteins can be globular or fibrous. Globular proteins are generally compact, soluble, and spherical in shape. Fibrous proteins are typically elongated and insoluble. Globular and fibrous proteins may exhibit one or more types of protein structures. 

At structural levels, proteins can be of four types, primary, secondary, tertiary, and quaternary. These levels determine the shape and function of a protein and are distinguished from one another by the degree of complexity in a polypeptide chain. The primary level is the most basic and rudimentary while the quaternary level describes sophisticated bonding.

Based on the chemical makeup and composition, proteins can be of seven types. These include antibodies, contractile proteins, enzymes, hormonal proteins, structural proteins, storage proteins, and transport proteins.

1. Antibodies

Antibodies are specialized proteins that defend the body against antigens or foreign invaders. Their ability to travel through the bloodstream enables them to be utilized by the immune system to identify and defend against bacteria, viruses, and other foreign intruders in blood. One way antibodies counteract antigens is by immobilizing them so that they can be destroyed by white blood cells.

2. Contractile Proteins

Contractile proteins are responsible for muscle contraction and movement. Examples of these proteins include actin and myosin. Eukaryotes tend to possess copious amounts of actin, which controls muscle contraction as well as cellular movement and division processes. Myosin powers the tasks carried out by actin by supplying it with energy.

3. Enzymes

Enzymes are proteins that facilitate and speed up biochemical reactions, which is why they are often referred to as catalysts. Notable enzymes include lactase and pepsin, proteins that are familiar for their roles in digestive medical conditions and specialty diets.

Lactose intolerance is caused by a lactase deficiency, an enzyme that breaks down the sugar lactose found in milk. Pepsin is a digestive enzyme that works in the stomach to break down proteins in food—a shortage of this enzyme leads to indigestion.

Other examples of digestive enzymes are those present in saliva: salivary amylase, salivary kallikrein, and lingual lipase all perform important biological functions. Salivary amylase is the primary enzyme found in saliva and it breaks down starch into sugar.

4. Hormonal Proteins

Hormonal proteins are messenger proteins that help coordinate certain bodily functions. Examples include insulin, oxytocin, and somatotropin. Insulin regulates glucose metabolism by controlling blood-sugar concentrations in the body. Oxytocin stimulates contractions during childbirth. Somatotropin is a growth hormone that incites protein production in muscle cells.

5. Structural Proteins

Structural proteins are fibrous and stringy, this formation making them ideal for supporting various other proteins such as keratin, collagen, and elastin. Keratins strengthen protective coverings such as skin, hair, quills, feathers, horns, and beaks. Collagen and elastin provide support to connective tissues like tendons and ligaments.

6. Storage Proteins

Storage proteins reserve amino acids for the body until ready for use. Examples of storage proteins include ovalbumin, which is found in egg whites, and casein, a milk-based protein. Ferritin is another protein that stores iron in the transport protein, hemoglobin.

7. Transport Proteins

Transport proteins are carrier proteins that move molecules from one place to another in the body. Hemoglobin is one of these and is responsible for transporting oxygen through the blood via red blood cells. Cytochromes, another type of transport protein, operate in the electron transport chain as electron carrier proteins.

Function and Uses of Proteins

Protein, the name itself is derived from a Greek word meaning primary. Hence proteins are indeed the most efficient primary molecule the body requires.

Proteins play an important role in the growth and maintenance of the human body. It breaks down the amino acid constituent and uses it efficiently when one falls ill or during the time of breastfeeding etc. Enzymes may also function outside the cell, such as digestive enzymes like lactase and sucrase, which help digest sugar.

Bodily functions that depend on enzymes include digestion, energy production, blood clotting, and muscle contraction. Some proteins are hormones which are chemical messengers that aid communication between the body cells, tissues, and organs.

They’re made and secreted by endocrine tissues or glands and then transported in the blood to their target tissues or organs where they bind to protein receptors on the cell surface. The fibrous proteins provide cells with shape, structure, and rigidity.

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