Enzymes

Question 1

What is a catalyst

Answer 1

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

Question 2

What is an enzyme

Answer 2

Catalysts produced by living things

Question 3

What do enzymes in our body do?

Answer 3

Reduce the need for high temperatures in the body, as they only speed up useful chemical reactions (called metabolic reactions)

Question 4

What are all enzymes?

Answer 4

Proteins, made up of chains of amino acids. These chains are folded into unique shapes so enzymes can do their job properly

Question 5

What do chemical reactions involve

Answer 5

Things being split up or joined together

Question 6

What is a substrate

Answer 6

A molecule changed in a reaction

Question 7

What do all enzyme molecules have?

Answer 7

An active site

Question 8

What is an active site?

Answer 8

The part where a substrate joins on to the enzyme

Question 9

Why do enzymes only speed up one reaction?

Answer 9

For an enzyme to work, a substrate has to be the correct shape to fit into the active site. This is called a “lock and key” model.

Question 10

What does changing the temperature change?

Answer 10

The rate of an enzyme-catalysed reaction. A higher temperature increases the rate, and a lower temperature decreases the rate

Question 11

Why does a higher temperature increase the rate of an enzyme-catalysed reaction

Answer 11

More heat means the enzymes and the substrate particles have more energy, and move about more, so they are more likely to meet up and react - they have a higher collision rate.

Question 12

What happens to an enzyme if the temperature is too hot?

Answer 12

Some of the bonds holding the enzyme together will break and the enzyme will lose its shape. It’s active site won’t fit the shape of the substrate any more, and it can’t catalyse the reaction so the reaction stops. The enzyme cannot function. It is said to be denatured, and it’s change in shape is irreversible.

Question 13

What is the optimum temperature

Answer 13

The temperature the reaction goes fastest. It is the temperature before it gets too hot and starts to denature.

Question 14

What is the optimum temperature for the most Important human enzymes?

Answer 14

37 degrees Celsius

Question 15

What does the enzyme catalase do?

Answer 15

Catalysed the breakdown of hydrogen peroxide into water and oxygen

Question 16

How can you measure how fast a product appears?

Answer 16

Use catalase to break down hydrogen peroxide solution into water and oxygen. The oxygen will then travel through a delivery tube from a test tube placed in a water bath into a measuring cylinder. The amount of oxygen produced per minute is measured

Question 17

In measuring how fast a product appears, what variable might you want to control?

Answer 17

Enzyme concentration, pH, volume of solution

Question 18

How to measure how fast a substrate disappears

Answer 18

Amylase converts starch to maltose. It is easy to detect starch (the substrate) using iodine solution; if starch is present, it will turn from browny-orange to blue-black. You can time how long it takes for the starch to disappear by regularly sampling the starch solution, and use the times to compare rates. By adjusting the water bath temperature you can see how temperature affects the activity of amylase.

Question 19

How does pH affect enzymes?

Answer 19

If it’s too high or low, the pH interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme. All enzymes have an optimum pH. It is often pH7 but not always

Question 20

What pH does pepsin work best at?

Answer 20

Pepsin is used to break down proteins in the stomach so it works best at pH2 to suit the acidic conditions.