Structure and function of specific biological molecules

Enzymes are biological catalysts that speed up biochemical reactions in the body without being used up in the process.
Each enzyme is made up of a long chain of amino acids which is folded into a unique shape. This shapes includes an active site that fits particular molecules.
The molecule that fits into the enzyme is known as the substrate. The substrate binds to the enzyme’s active site forming an enzyme-substrate complex.
After the reaction, the products, now different to the substrate, leave the active site. The enzyme can then take part in the same reaction again.

DNA, or deoxyribonucleic acid, is a molecule that carries most of the genetic instructions within the cell.
Its structure is a double helix, which resembles a twisted ladder. The sides of the ladder are composed of alternating sugar (deoxyribose) and phosphate groups.
The rungs of the ladder are made from pairing bases: adenine pairs with thymine, and cytosine pairs with guanine, held together by hydrogen bonds.
The order of these base pairs form the code for the production of proteins, which perform a vast array of functions within the body.

Hemoglobin is a protein molecule found in red blood cells responsible for transporting oxygen from the lungs to the body’s tissues.
Each hemoglobin molecule is made up of four polypeptide chains (two alpha and two beta chains) and contains an iron containing part called heme group.
Oxygen binds to the iron atom in the heme group in the lungs to form oxyhemoglobin. This process is reversible, so oxygen is released from oxyhemoglobin in tissues where it is needed.

Antibodies are proteins that are produced by the body’s immune system in response to foreign substances like bacteria and viruses.
Each antibody molecule is comprised of four polypeptides – two light chains and two heavy chains, arranged in a ‘Y’ shape.
The variable region of the antibody can bind to a specific antigen on the foreign substance, marking it for destruction. The base of the ‘Y’ interacts with immune cells.
They also act as a messenger, calling upon the immune system to destroy the pathogens.

Collagen is the most abundant protein in the animal kingdom and forms the primary structural element in skin, bones, tendons, and teeth.
The collagen molecule is a long, stiff, triple-stranded helical structure in which three collagen polypeptides are wound around one another in a rope-like arrangement.
The high tensile strength of collagen helps to withstand stretching forces, providing firmness to our skin and strength to our bones.