Enzymes

Enzymes break down substances by: 

• Lowering the activation energy, a substance with a complementary shape to the enzyme entries the active site, forming an enzyme substrate complex, the active site changes shape to mould around the substrate (induced fit), this weakens the bonds in the substrate (lowering the activation energy) by stretching and distorting them, the bonds are broken, the products then leave the active site, leaving the enzyme unchanged. 

The effect of pH on the rate of enzyme activity: 

• Changes in pH affect the charges on the R groups of the amino acids at the active site. Therefore the interactions between the enzyme and the substrate are disrupted, reducing the frequency of enzyme substrate complexes forming, 
• Mote extreme pH conditions can cause the bonds (hydrogen, ionic, disulphide) holding the tertiary structure, to break. 
• If the enzyme denatures then the active site is no longer complementary to the substrate, therefore no enzyme substrate complexes can form. 

How the shape of the enzyme/protein molecules is suited to its function:

• Enzyme has a specific primary structure (amino acid sequence), this sequence determines where the hydrogen bonds will form during development of the secondary structure.Proteins have a unique tertiary structure held together by ionic, hydrogen and disulphide bonds. Globular proteins have an active site with unique structure. 
• The shoe of the active site is complementary to the substrate, so it'll only fit that substrate, so that enzyme substrate complexes can form.

The effect of temperature on the rate of enzyme activity: 

• As temperature increases dodoes the rate of the reaction, as the substrates gan kinetic energy and therefore collide more frequently, therefore there are more enzyme substrate complexes forming.
• A further increase of temperature can cause bonds (ionic, disulphide and hydrogen) which are holding the tertiary structure of the enzyme inlace to begin to break, this means the enzyme denature. 
• The active site no longer complements the substrate, therefore no enzyme substrate complexes can form.

How does an enzyme catalyse a condensation reaction: 

• The enzyme has a complementary shape to the substrate, meaning an enzyme substrate complex can be formed, the reactive groups are brought close together, the change in the active site (induced fit) lowers activation energy, water is removed and a bond is formed (glycosidic, peptide or ester bond) The products leave the active site, the enzyme remains unchanged

How do inhibitors affect enzyme activity:

• There are two types of inhibitors, competitive and non-competitive:  

• Competitive inhibitors -  have a similar shape to the substrate they can enter and bind with the active site, preventing enzyme substrate complexes forming, this problem can be  overcome by increasing the substrate concentration, 

• Non-competitive inhibitors -  have a different shape and bind to the enzyme at any point other than the active site, causing a change in the shape of the active site meaning the enzyme is no longer complementary to the substrate, preventing the formation of enzyme substrate complexes.