Enzymes and Investigating Enzyme Activity

Question 1

What is an enzyme?

Answer 1

An enzyme is a biological catalyst and almost always a protein. It speeds up the rate of chemical reactions in the cell, and they are able to be used multiple times.

Question 2

How can you make a reaction happen more quickly?

Answer 2

Raising the temperature

However, this would speed up the useful reactions as well as the unwanted ones. There is also a limit to how far you can raise the temperature inside a living creature before its cells start getting damaged.

Question 3

What is a biological catalyst?

Answer 3

A catalyst is a substance which increases the speed of a reaction, without being changed or used up in the reaction.

Question 4

What are the useful chemical reactions in the body caused by enzymes called?

Answer 4

Metabolic Reactions

Question 5

What are proteins made up of?

Answer 5

They are made up of chains of amino acids. These chains are folded into specific shapes, which enzymes need to do their jobs.

Question 6

What is a substrate?

Answer 6

A molecule that is changed in a reaction.

Question 7

Every enzyme molecule has an active site. What happens here?

Answer 7

This is the part where a substance joins on to the enzyme.

Question 8

Why do enzymes usually only speed up one reaction?

Answer 8

For an enzyme to work, a substrate has to be the correct shape to fit into the active site.

Question 9

How do enzymes react to a higher, optimum temperature?

Answer 9

A higher temperature increases the rate of an enzyme-catalysed reaction. The enzymes and substrate have more energy, so they move about more and are more likely to collide and form enzyme-substrate complexes. All enzymes have an optimum temperature that they work best at.

Question 10

How do enzymes react when the temperature gets too high?

Answer 10

If it gets too hot, some of the bonds holding the enzyme together break. This changes the shape of the enzyme’s active site, so the substrate won’t fit anymore. The enzyme is said to be denatured.

Question 11

How does the pH being too high or too low affect an enzyme?

Answer 11

If the pH is too high or too low, it interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme.

Question 12

What is usually an enzyme’s optimum pH?

Answer 12

Neutral pH 7

Question 13

You can investigate how temperature affects enzyme activity. How can you measure how fast a product appears?

Answer 13

1. The enzyme catalase catalyses the breakdown of hydrogen peroxide into water and oxygen.
2. You can collect the oxygen and measure how much is produced in a set time.
3. Use a pipette to add a set amount of hydrogen peroxide into a boiling tube. Put the tube in a water bath at 10°C.
4. Set up the rest of the apparatus. Add a source of catalase (e.g. 1 cm³ of potato) to the hydrogen peroxide and quickly attach the bung.
5. Record how much oxygen is produced in first minute. Repeat three times and calculate the mean.
6. Repeat at 20°C, 30°C and 40°C.
7. Control any variables (e.g. pH, the potato used, the size of the potato pieces, etc.) to make it a fair test.

Question 14

You can investigate how temperature affects enzyme activity. How can you measure how fast a product disappears?

Answer 14

1. The enzyme amylase catalyse the breakdown of starch to maltose.
2. It’s easy to detect starch using iodine solution - if starch is present, the iodine solution will change from browny-orange to blue-black.
3. Set up the apparatus. Put a drop of iodine solution into each well on the spotting tile.
4. Every ten seconds, drop a sample of the mixture into a well using a pipette. When the iodine solution remains browny-orange (i.e. starch is no longer present), record the total time taken.
5. Repeat with the water bath at different temperatures to see how it affects the time taken for the starch to be broken down. Remember to control all of the variables each time.

Question 15

How can you investigate how pH affects enzyme activity?

Answer 15

1. You can adapt the experiments mentioned in the other flashcards to investigate the effect of pH on enzyme activity.
2. Follow the same methods mentioned previously, but add a buffer solution with a different pH level to a series of different tubes containing the enzyme-substrate mixture.
3. As before, control any variables - use the water bath to keep the temperature of the reaction mixture the same for each pH, and make sure volumes and concentrations are kept the same.