enzymes

Question 1

what is an enzyme

Answer 1

a biological catalyst that speeds up the rate of reaction without being used up itself

Question 2

lock & key enzyme method:

Answer 2

1. the substrate collides with the active site and forms enzyme substrate complex
2. the enzyme catalyses the substrate
3. products are released from the active site
4. enzyme remains unchanged so can be reused

Question 3

four factors that affect the activity rate of enzymes:

Answer 3

1. temperature
2. pH
3. substrate concentration
4. enzyme concentration

Question 4

what happens as enzymes and substrates are heated?

Answer 4

• rate of reaction increases
• molecules have more kinetic energy, so move faster
• more collisions

Question 5

what happens when enzymes are heated past their optimum temp?

Answer 5

they denature
- heat causes the amino acids in the enzyme to unfold so it changes its structure
- the substrate molecules can no longer fit in the active site

Question 6

optimum pH in the stomach

Answer 6

pH2

Question 7

optimum pH in the small intestine

Answer 7

pH7

Question 8

what happens if the enzyme/substrate concentration becomes too high

Answer 8

will become saturated so ROR will plateau

Question 9

how does the pH affect the enzyme either side of the optimum

Answer 9

it changes the shape of the active site, so it denatures

Question 10

method to investigate effect of pH on the activity on enzymes

Answer 10

1) add 2cm^3 of different pH buffers (7, 8, 9, or 10) to different test tubes
2) add 2cm^3 of protease enzyme to each test tube
3) staple 1cm x 1cm square of photographic film onto wooden splints
4) place one splint into each of the test tubes and start a stopwatch (it should take 10 - 15 mins)
5) move the film
6) measure how long it takes for the film to become transparent

Question 11

results of the effect of pH on enzymes practical

Answer 11

• the pH of buffer and protease solution increases, the time taken for photographic film to appear clear increases