Table of Contents
About Protein
Protein comes from the Greek word proteas. It means first or primary. Some proteins speed up chemical reactions. They are protection, storage, transport, cellular communication, movement, or structural support. They are all built from the same 20 amino acids, held together by unbranched polymers.
What Is The Protein Structure ?
A peptide bond is a bond formed by two amino acids. So a polymer of amino acids is called a polypeptide. A protein is a biologically active molecule of one or more polypeptides. Each is folded and rolled into a specific three dimensional shape. Amino acid monomers are amino acids that all share. An amino acid is an organic molecule containing amino and carboxyl groups.
When two amino acids are placed, the carboxyl group of one is adjacent to the amino group of the other. This bond is also called a peptide bond. Most likely, it comes from a polypeptide. A polymer of several amino acids linked by peptide bonds.
Four Levels Of Protein Structure:
Proteins have three superimposed levels of a structure known as primary, secondary, and tertiary structure. The fourth level of quaternary structure arises when a protein consists of two or more polypeptide chains. The primary structure of a protein is its amino sequence.
Most proteins have multiple subunits in their polypeptide chains. The overall structure of the protein is folded. These coils and folds indicate that it is a secondary structure. The polypeptide backbone (not the amino acid side chains) results from hydrogen bonds between repeating units. One such secondary structure is the alpha helix; the other major type of secondary structure is the beta fold sheet.
The shape of the tertiary structure results from the interactions between the side chains (R groups) of the various amino acids resulting in a polypeptide. Quaternary structure is the protein structure resulting from the assembly of these polypeptide subunits.
Most proteins are almost spherical (globular proteins), while others are shaped like long fibers (fibrous proteins).
Functions Of Protein
Proteins That Catalyze Enzymes
Function: Chemical reactions can be accelerated selectively.
Examples: Digestive enzymes catalyze bond hydrolysis in food molecules.
Storage Proteins
Function: Storage of amino acids
Examples: Casein, the protein in milk, is the main amino acid. Plant seeds contain storage proteins.
Ovalbumin is a protein of egg white, which contains an amino acid source.
Hormonal Proteins
Function: Coordinating the activities of an organism
Example: Insulin, a hormone secreted by the pancreas, causes other causes
The tissue absorbs glucose, thereby regulating blood sugar concentration.
Contractile And Motor Proteins
Function: Movement
Examples: Motor proteins are responsible for the movement of cilia and flagella. Actin and myosin proteins are responsible for muscle contraction.
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Defense Proteins
Function: Provides protection against disease.
Example: Antibodies are released and are useful in killing viruses and bacteria.
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Transport Proteins
Function: Transport of materials
Examples: Hemoglobin is an iron-containing protein
The circulatory system transports oxygen from the lungs to the rest of the body. Other proteins transport molecules across membranes.
Receptor Proteins
Function: Cell’s response to chemical stimuli
Example: Gravity is a potential built into the membrane of a nerve cell. Other nerve cells release signaling molecules.
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Structural proteins
Function: Support
Examples: Keratin is the protein of hair, horns, feathers, and other skin. Insects and spiders use silk fibers to make their cocoons and webs, respectively. The fibrous framework in animal connective tissues is provided by collagen and elastin proteins.