B2 Enzymes (page 25)

Question 1

Finish the sentence;

Chemical reactions are what make you work, and enzymes are………

Answer 1

what make them work.

Question 2

What are Enzymes?

Answer 2

they are catalysts produced by Living Things.

Question 3

Living things have what going on inside them all the time?

Answer 3

they have thousands of different chemical reactions going on inside them all the time.

Question 4

Why do chemical reactions inside living things need to be carfully controlled?

Answer 4

to get the right amounts of substances.

Question 5

How can you usually make a reaction happen more quickly?

Answer 5

by raising the temperature. This would speed up the useful reactions but also the unwanted ones too…(not good).

Question 6

Is there a limit to how far you can rise the temperature inside a living creature and why?

Answer 6

yes there is a limit to how far you can raise the temperature inside a living creature as the cells start getting damaged.

Question 7

Living things produce enzymes that act as biological catalysts. explain what this is?

Answer 7

Ezymes reduce the need for high temperatures and we only have enzymes to speed up the useful chemical reactions in the body.

Question 8

Explain what a Catalyst is?

Answer 8

it is a substance which INCREASES the speed of a reaction, without being CHANGED or USED UP in the reaction.

Question 9

Enzymes are all large proteins, what do this mean?

Answer 9

all proteins are made up of chains of amino acids. These chains are folded into unique shapes, which enzymes need to do their jobs (see below).

Question 10

Why do Enzymes have special shapes?

Answer 10

so they can catalyse Reactions.

Question 11

Chemical reactions usually involve what?

Answer 11

things either being split aprt of joined together.

Question 12

Every enzyme has an active site, explain what this is?

Answer 12

they have an active site, with a unique shape that fits onto the substance involved in a reaction.

Question 13

Why are Enzymes really picky?

Answer 13

they usually only catalyse one specific reaction. This is because, for the enzyme to work, the substrate has to fit into its active site. If the substrate doesn’t match the enzyme’s active site, then the reaction won’t be catalysed.

(substrate means the surface on which an organism (e.g. plant, fungus or animal) lives or the substance on which an enzyme can act).

Question 14

On page 25, 5), look at the diagram, it shows the ‘lock and key’ model of enzyme action. Explain how it works?

Answer 14

This is simpler than how enzymes actually work. In reality, the acive site changes shape a little as the substrate binds to it to get a tighter fit. This is called the ‘INDUCED FIT’ model of enzyme action.

Question 15

What is the substance called that an enzyme acts on?

Answer 15

the substrate.

Question 16

Do Enzymes need the right Temperature and pH?

Answer 16

Yes.

Question 17

Changing the temperature changes the rate of what?

Answer 17

changes the rate of an enzyme-catalysed reaction.

Question 18

Like with any reaction, a higher temperature increases the rate at first, but what happens if the enzyme gets too hot?

Answer 18

some of the bonds holding the enzyme toegether break.

Question 19

What happens if the bonds holding the enzyme together break?

Answer 19

This changes the shape of the enzyme’s active site, so the substrate won’t fit any more. The enzyme is said to be denatured. (denatured basically means the key will no longer fit the lock)

Question 20

All enzymes have an optimum temperature, what do this mean?

Answer 20

that they work best at.

(optimum means the most fabourable situation/temperture)

Question 21

How do a pH affects enzymes?

Answer 21

if its too high or too low the pH interfered with the bonds holding the enzyme togeher. This changes the shape of the active site and denatures te enzyme.

(denature means the enzyme key will no longer fit the lock).

Question 22

All enzymes have an optimum pH that they work best at, what is the optimum pH?

Answer 22

it’s often neutral pH 7, but not always - e.g. pepsin is an enzyme used to break down proteins in the stomach. It works best a pH 2, which means it’s well-suited to the acidic conditions there.

look at diagrams on pg 25 of the optimum temperture and optimum pH where the enzyme is most active.

Question 23

Explain why enzymes have an optimum pH? (2 marks)

Answer 23

If the pH is too high or too low, it can interfere with the bonds holding the enzyme together. This changes the shape of the active site (1 mark) and denatures the enzyme (1 mark)

(make sure you use the special terms like ‘active site’ and ‘denatured’ - examiners will love it.