factors affecting enzyme reaction rates

Question 1

what are the factors affecting enzyme reaction rates?

Answer 1

temperature, pH, coenzymes, substrate concentration, enzyme concentration and inhibitors

Question 2

how does temperature affect enzyme reaction rates?

Answer 2

1. increasing temperature
   - increases random movement of molecules
   - increases molecular interactions
   - increases rate of reactions
2. optimal temperature
   - the temperature at which catalytic activity is greatest.
   - each enzyme has its own specific optimal temperature e.g. mammalian enzymes optimal at 37 degrees celsius
3. critical temperature
   - the temperature that denatures the enzyme
   - e.g. mammalian enzymes ~ 40 degrees celsius

Question 3

how does pH affect enzyme reaction rates?

Answer 3

1. optimal pH is when the enzyme and substrate fit together best
2. small changes in pH above or below the optimum do not cause a permanent change to the enzyme, since the bonds can be reformed. extreme changes in pH can cause enzymes to denature and permanently lose their function
   e.g. amylase (digestive enzyme in saliva) -> pH 7
   pepsin (digestive enzyme in stomach) -> pH 1-2
   trypsin (digestive enzyme in small intestine) -> pH 8

Question 4

what are coenzymes and how do they affect enzyme reaction rates?

Answer 4

1. coenzymes are molecules that are required by certain enzymes to carry out the reaction. they bind to the active site of the enzyme and participate in the reaction but are not considered substrates of the reaction
2. they are essential for enzyme activity
3. e.g. vitamins, NAD, NADH, FAD

Question 5

how does substrate concentration affect enzyme reaction rates?

Answer 5

1. as substrate concentration increases, reaction rate increases
2. a maximal reaction rate is reached
3. amount of enzyme or other factor may become limiting

Question 6

how does enzyme concentration affect enzyme reaction rates?

Answer 6

1. as enzyme concentration increases, reaction rate increases
2. a maximal rate is reached
3. amount of substrate or other factor may become limiting

Question 7

what are enzyme inhibitors and how do they affect enzyme reaction rates?

Answer 7

1. competitive inhibitors
   - bind to active site
   - prevent substrate binding
   - effects can be reduced by increasing substrate concentration
2. non-competitive inhibitors
   - bind outside active site
   -> changes in protein shape
   -> changes shape of active site
   - substrate cant bind to the active site
   - effects can not be reduced by increasing substrate concentration