Enzymes

Structure

• tertiary globular proteins
• protein chain folded back on itself into spherical or globular shape
• own sequence of amino acids
• held in tertiary form by hydrogen bonds, disulphide bridges and ionic bonds
• complex 3D shape
• large molecule but only active site is functional

How they work

• biological catalysts that speed up metabolic reactions
• large molecules broken down into smaller molecules
• smaller molecules built up into larger, more complex molecules
• react with a substrate

Enzyme + substrate ----> enzymes-substrate complex ----> enzyme + product

Properties

• specific - each enzyme will catalase only one particular reaction, e.g. sucrase acts on sucrose
• very efficient and have high turnover number - can convert many molecules of substrate per unit time, e.g. catalase which breaks down the waste product hydrogen peroxide in the body has a turnover of several million
• chemical reactions need energy to start them (activation energy). Needed to break existing chemical bonds inside molecules. Enzymes lower activation energy of a reaction reducing the input energy needed and allowing reactions to occur at lower temperatures

Factors

• made inside living cells but may act inside (intracellular) or outside (extracellular) a cell
• environmental conditions, e.g. temperature and pH change 3D structure of enzyme molecules. Bonds are broken and the configuration of the active site is altered

Temperature

• increase in temp increase kinetic energy so they move around…