Keywords

Activation energy: The energy required to enable a reaction to take place.

Active site: The area on an enzyme molecule to which the substrate binds.

Buffer: A substance that resists a change in pH when acid or alkali is added.

Catalyst: A substance that increases the rate of a reaction but does not take part in the reaction, and so is reusable.

Coenzyme: An organic, non-protein molecule that binds temporarily with the substrate to an enzyme active site. It is essential for enzyme activity.

Cofactor: A molecule or ion that helps an enzyme to work. It may be an inorganic ion or a coenzyme.

Competitive inhibitor: A substance that reduces the rate of an enzyme-controlled reaction by binding to the enzyme’s active site.

Denaturation: An irreversible change in the tertiary structure of a protein molecule. It leads to loss of function in most proteins.

End-product inhibition: The regulation of metabolic pathways where the last product in a sequence of enzyme-controlled reactions becomes an inhibitor of one of the enzymes earlier in the sequence.

Enzyme: Biological catalyst that speeds up metabolic reactions inside cells.

Enzyme-substrate complex: The intermediate structure formed when a substrate molecule binds to an enzyme active site.

Globular protein: Proteins with relatively spherical molecules, soluble in water, often having metabolic roles in organisms.

Induced fit hypothesis: The theory of enzyme action in which the enzyme molecule changes shape to fit the substrate molecule more closely as it binds to it.

Inhibition: The slowing of an enzyme-controlled reaction by a substance that slows or prevents the formation of enzyme-substrate complexes.

Lock and key hypothesis: The theory of enzyme action where the enzyme active site is complementary to the substrate molecule.

Metabolism: All the chemical reactions that take place inside the cells of an organism.

Non-competitive inhibitor: An inhibitor of an enzyme-controlled reaction that binds to the enzyme at an allosteric site.

Peptide bond: The covalent bond formed when amino acids are joined together in condensation reactions.

Polypeptide: A polymer consisting of many amino acid monomers covalently bonded together by peptide bonds.

Prosthetic group: A non-protein group covalently attached to a polypeptide.

Substrate: The substance that is used up in an enzyme-controlled reaction, leading to the formation of a product. It binds to the active site of the enzyme at the start of the reaction.

Turnover: Rate at which an enzyme converts substrate into product.