Enzymes

Question 0

What is the function of an enzyme?

Answer 0

To control all the reactions in the cell

Question 1

What’s makes an active site in the enzyme

Answer 1

The shape of the protein molecule

Question 2

What can denature an enzyme?

Answer 2

Heat or pH levels

Question 3

What is the active site?

Answer 3

The small area on its surface.

Question 4

How do enzymes work?

Answer 4

The substrate enters the enzymes active site, and attaches to it. This lowers the energy needed for the reaction to start, allowing products to down more easily. The reaction takes place and products are formed.

Question 5

What is an enzyme?

Answer 5

A biological catalyst: they speed up the reaction without being used themselves. Afterwards they are unchanged and free to catalyse more reactions.

Question 6

How would you investigate the effect of temperature on enzyme activityby measuring how fast a substrate disappears?

Answer 6

Amylase breaks starch down into maltose. Measure the speed at which the starch disappears using iodine solution (turns from blue to browny/orange)

1. Spots of iodine solution are placed on a sporting tile.
2. 10 cm3 starch solution and amylase enzyme in a water bath at a constant temperature (10degrees)
3. Immediately take a small sample and add it to the first drop of iodine solution on the tile.
4. Time how long it takes for the starch to disappear by regularly sampling the starch solution, and use the times to compare rates between different tests
5. Repeat the experiment at 20, 30, 40 and 50 degrees and compare the results
   Control variables: volume and concentration of starch and amylase solution, volume of iodine solution

Question 7

Where do enzymes catalyse reactions?

Answer 7

In the cytoplasm

Question 8

How does the cell control the activities?

Answer 8

The nucleus contains the genes, which control the production of enzymes, which catalyse reactions in the cytoplasm.

Question 9

Why are enzymes needed?

Answer 9

Body temperatures are low (about 37°C) and most of the reactions that happen in cells would be far too slow to allow life to go on without catalysts.

Question 10

What is a substrate?

Answer 10

The molecule that an enzyme acts on.

Question 11

Why is it called a ‘lock and key’ model?

Answer 11

The substrate fits into the active site rather like a key fitting into a lock.

Question 12

What temperature do enzymes work best at?

Answer 12

Enzymes in the body have evolved to work best at 37°, this is the optimum temperature.

Question 13

At what temperature roughly are enzymes in the body denatured?

Answer 13

40°C

Question 14

What is the pH inside cells?

Answer 14

Around 7, neutral. Enzymes have adapted to work at this temperature.

Question 15

Why are reactions faster at higher temperatures?

Answer 15

The molecules of enzyme and substrate have more kinetic energy so they collide more often. More collisions mean the reaction will take place more frequently.

Question 16

What is special about pepsin?

Answer 16

It works in the stomach which produces hydrochloric acid. Although enzymes usually stop working at this low a pH pepsin is adapted to work at a pH of about 2.

Question 18

What is special about pepsin?

Answer 18

It works in the stomach which produces hydrochloric acid. Although enzymes usually stop working at this low a pH pepsin is adapted to work at a pH of about 2.

Question 19

How would you measure the effect of temperature on enzyme activity by measuring how fast a product appear?

Answer 19

The enzyme catalase catalyses the breakdown of hydrogen peroxide into water and oxygen
1) put a test tube of hydrogen peroxide solution with a source of catalase in it e.g. potato into a water bath at 10 degrees
2) put a bung on the top of the test tube and connect it to a delivery tube
3) put the other end of the delivery tube into an upside down measuring cylinder in a bowl of water
4) measure how much oxygen is given off in one minute
5) repeat with the water bath at 20, 30, 40 and 50 degrees
Control variables: enzyme concentration, volume of hydrogen peroxide solution, pH