Enzymes

Question 1

Define ‘enzymes’

Answer 1

Catalysts produced by living things

Question 2

Living organisms have thousands of different ____ ____ going on inside them all the time

Answer 2

Living organisms have thousands of different chemical reactions going on inside them all the time

Question 3

What needs to be done to the chemical reactions going on in your body, and why?

Answer 3

They need to be carefully controlled

To get the right amounts of substances

Question 4

What usually causes a reaction to speed up?

Answer 4

Raising the temperature

Question 5

Name 2 disadvantages of raising the temperature to speed up a reaction in your body

Answer 5

1. As well as speeding up the useful reaction it will likely speed up the unwanted ones too…
2. Raising the temperature too far damages cells

Question 6

What do enzymes act as?

Answer 6

Biological catalysts

Question 7

Name 2 advantages of enzymes

Answer 7

1. They reduce the need for high temperatures
2. We only have enzymes that speed up the useful chemical reactions in the body

Question 8

Define a catalyst

Answer 8

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

Question 9

What are enzymes, and what is this substance made out of?

Answer 9

Enzymes are proteins, which are made up of chains of amino acids

Question 10

Explain the importance of the shape of the chains of amino acids the make up enzymes

Answer 10

These chains are folded into unique shapes, which enzymes need to do their jobs

Question 11

Name the 3 things that proteins act as (other than catalysts)

Answer 11

1. Structural components of tissue (e.g. muscle)
2. Hormones
3. Antibodies

Question 12

Why do enzymes have ‘special shapes’?

Answer 12

So they can CATALYSE REACTIONS

Question 13

What 2 things do chemical reactions usually involve happening to things (2)?

Answer 13

1. Splitting things apart
2. Joining things together

Question 14

Every enzyme has a unique shape that ____ onto the ____ involved in the ____

Answer 14

Every enzyme has a unique shape that fits onto the substances involved in the reaction

Question 15

How many reactions do enzymes usually catalyse?

Answer 15

Only one

Question 16

Why are enzymes like keys?

Answer 16

Because they need to be the right shape to catalyse a reaction, like keys have to be the right shape to open a lock (and stereotypically, only one shaped key will fit a lock)

Question 17

What 2 conditions affect the rate of an enzyme-catalysed reaction?

Answer 17

1. Temperature
2. pH

Question 18

Describe how a graph with rate of enzyme-catalysed reaction on the y axis and temperture on the x axis would look

Answer 18

1. Rate of reaction would increase slowly then rapidly at first as temp increased
2. Then the rate slightly plateaus as it reaaches optimum temp (37^oC)
3. Then the rate of reaction rapidly decreses until it reaches 0

Question 19

Explain why the rate of an enzyme-catalysed reaction decreases when it gets hotter than 37^oC

Answer 19

If it gets too hot, some of the bonds holding the enzyme together will break. This destroys the enzymes special shape, so it doesn’t work any more.

Question 20

What is it called when the shape of an enzyme is changed so it doesn’t work any more?

Answer 20

It’s said to be denatured

Question 21

What happens to enzymes if the pH of the conditions they’re in is too high or too low?

Answer 21

It interferes with the bonds holding the enzymes together, changing its shape and denaturing it

Question 22

What is often the optimum pH for enzymes?

Answer 22

pH7

Question 23

Name an enzyme that has a different optimum pH to the usual pH 7

Give detail

Answer 23

Pepsin

Breaks down proteins in the stomach and works best in acidic conditions - pH 2

Question 24

What pH do enzymes in the small intestine prefer?

Answer 24

High pHs

(alkaline conditions)