The importance of enzymes

Question 1

amylase

Answer 1

breaks down starch

Question 2

catalyse

Answer 2

breaks down hydrogen peroxide

Question 3

starch synthase

Answer 3

makes starch from glucose

Question 4

synthesis

Answer 4

when two substances chemically join

Question 5

DNA polymerase

Answer 5

synthesis of DNA from it’s monomers

Question 6

Protein

Answer 6

breaks down into amino acids

Question 7

Starch/carbohydrates

Answer 7

breaks down into glucose/sugars

Question 8

Lipids

Answer 8

breaks down into fatty acids and glycerol

Question 9

Polymers

Answer 9

monomers joined together

Question 10

Monomers

Answer 10

small molecules

Question 11

calculation for rate of reaction

Answer 11

1/time

Question 12

What type of reactions do enzymes catalyse?

Answer 12

they synthesise large molecules from smaller ones

they break down large molecules into smaller ones

Question 13

Are enzymes used up in reactions?

Answer 13

no

Question 14

Name one example of an enzyme and the reaction it catalyses.

Answer 14

amylase
breaks down starch into glucose

starch synthase
synthesises starch from glucose

Question 15

People with cystic fibrosis have thick mucus lining their gut. They have to take capsules containing enzymes before meals. Explain why.

Answer 15

The thick mucus prevents enyzmes being secreted into the gut.
If they didn’t take enzyme capsules before meals, their food would not be digested into smaller, soluble molecules.
As a result, they would not absorb enough nutrients.

Question 16

The enzymes that digest lipids will not digest proteins. Explain why.

Answer 16

The enzyme that digests lipids/lipase has a specific active site
only lipids will fit in/proteins will not fit in

Question 17

Where in a cell would you expect to find enzymes that synthesise amino acids into proteins?

Answer 17

ribosomes

Question 18

How do you calculate relative rate of reaction for a particular pH?

Answer 18

1/time

Question 19

Describe a practical used to investigate the effects of pH on amylase activity

Answer 19

1) add amylase to buffered starch solution in a test tube
2) place the tube in a water bath for a constant temperature
3) take samples of the mixture at regular intervals (e.g. every 10s) and mix them with a drop of iodine solution on a dimple tile
4) repeat the test until the iodine solution stops changing colour when the starch/amylase mixture is added - record the time taken for this to happen
5) repeat the procedure at different pH values

Question 20

Explain how you would determine the optimum pH from a graph showing the results of a practical used to investigate the effects of pH on amylase activity [2]

Answer 20

it will take the least time for the mixture of amylase/starch to stop reacting with the iodine solution

Question 21

A student repeated a practical used to investigate the effects of pH on amylase activity using solutions of pH 5.2, 5.6, 6.0, 6.4, and 6.8

Explain why the results of this experiment could produce a better answer for the optimum pH of the experiment than using solutions of pH 4, 4.5, 5.5, 6.0, 6.5, 7, 7.5, 8, 8.5, 9 [2]

Answer 21

the values of pH used are much closer together, so the results should produce a more accurate value for the optimum pH