Enzymes

• Enzymes increase ROR by lowering activation energy. Active site is the area where the substrate binds to the enzyme, enzymes are specific to only one substrates. When the enzymes and substrate form a complex the structure of the enzyme is altered so that the active site fits around the enzymes, this is called the induced fit model.
• Factors affecting the rate of enzyme controlled reactions: enzyme concentration (more active sites for substates to bind to, until substrate concentration becomes the limiting factor), substrate concentration (more enzyme-substrate complexes can form), temperature (rate of reaction increases to optimum temperature, it decreases over optimum- 37)
• Inhibitors: a substance that slows down the reaction by affecting the binding site of substrates, irreversible inhibitors include heavy metal ions which cause disulphide bonds to break in the protein structure, causing the active site to change which affects protein activity. Reversible inhibitors bind to the active site through hydrogen bonds and weak ionic interactions, they can be competitive or non-competitive.
• Competitive inhibitors are similar to the substrate molecule so they bind to the active site of the enzyme, non-competitive inhibitors bind to the enzyme at an alternative site which alters the shape of the active site and prevent the substrate from binding to it. For competitive inhibitors increasing the substrate concentration can increase ROR, this cannot happen for non-competitive inhibitors, so enzyme-substrate complexes are unable to form.
• Cofactor is non-protein compound required for enzyme activity, there are three types (coenzymes, activators and prosthetic groups).
• coenzymes: organic cofactors which do not bind permanently, they facilitate the binding of the substrate to enzyme, many coenzymes are vitamin derived.
• activators: inorganic metal ions which temporarily bind to the enzyme and alter the active site, making the reaction more feasible.
• Prosthetic groups are permanently attached to the enzyme, e.g haemoglobin contains a prosthetic haem group which contains ion.