Biology AS - Enzymes



Biological catalyst which speeds up chemical reaction Intracellular: work inside cells – e.g. Hydrogen Peroxide = water + oxygen

•Extracellular: work outside cells – e.g. Amylase = starch – maltose

Lock & Key: 1 substrate binds to enzyme

•Induced fit: Substrate changes shape of Active Site

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Cofactors and Coenzymes

Cofactors and Coenzymes:

•Inorganic Cofactors: ions or inorganic molecules help enzyme bind to substrate – not used up or changed

Cofactors: are changed and carry chemical groups between enzymes – recycled in this process

•Prosthetic group: a cofactor is tightly bound to the enzyme

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Enzyme Limiting Factors

Temperature: rate of reaction increasing till optimum temperature – causes denature

Temperature Coefficient: Q10 – change in rate of reaction with 10 degrees of change

pH: above or below optimum = H+  & OH- breaks hydrogen – causes denaturing

Enzyme Concentration: more likely to bind to substrate – but if limited then it has no effect

Substrate Concentration: more likely to bind to enzyme – but if limited then it has no effect

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Enzyme Inhibition

Competitive Inhibitor: inhibitor fits into active site and blocks substrate

Non-competitive Inhibitor: binds to allosteric site which denatures the Active Site

Reversible: weak hydrogen bonds or ionic bonds

•Non-reversible: strong covalent bonds

Drug Inhibitor: antiviral drugs which blocks replication of DNA to stop spreading

•Metabolic poisons: e.g. – Cyanide (non-competitive, non-reversible) stops cell respiration

Product Inhibition: regulates product production = the last substrate in the metabolic chain blocks the first enzyme

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