March 12th 2010

2.1.18 Enzymes are Globular Proteins

Catalyst Molecule/element that speeds up a chemical reaction but is not used up in the reaction and remains unchanged after the reaction
Globular proteins have specific tertiary structures. The shape comes from the protein’s primary structure (Sequence of amino acids) and it’s secondary structure. In globular proteins the tertiary structure usually has hydrophobic R groups in the centre and hydrophilic R groups around the outside of the ball.
Enzymes are:
Globular proteins and soluble in water
Able to break molecules down or build them up!
Biological catalysts
Specific- because they catalyse a reaction with only one type of substrate
Their globular structure has a pocket called an active site
Activity affected by temperature and pH (Rate of reaction)
Enzymes are large molecules with hundreds of amino acids. A lot of these amino acids work to keep the specific tertiary structure of the enzyme. The function of the enzyme depends on the shape, and for the enzyme to work correctly the tertiary structure must be maintained specifically.
All of the structures (primary, secondary, tertiary) of the enzyme is involved in the specific active site shape. (Where the catalytic activity of the enzyme happens)
Enzymes are faster than catalysts and because they are specific to one reaction they do not produce unwanted by products.
An individual cell could contain over one thousand enzymes to catalyse every process, like digestion, respiration, photosynthesis.
Enzyme Maltase
Enzyme Maltase

Substrate Product E.g. Matlose glucose + glucose

Enzyme | Reaction Catalysed | Lactase | Breaking down lactose into glucose and galactose monomers. Lactose intolerant people don’t have this enzyme so suffer bloating, stomach cramps when they ingest lactose. | Catalase | Breaking down hydrogen peroxide to water and oxygen gas. Most organisms produce catalase because hydrogen peroxide is a toxic by product of some metabolic reactions | Ribulose Biphosphate Carboxylase | Catalyses the binding of CO2 into ribulose biphosphate for photosynthesizing plants. | ATP-ase | Breaking down ATP for ADP and a phosphate group to realease energy to drive energy requiring processes like active transport | Glycogen Synthetase | Building glycogen by catalyzing/joining glucose molecules |