3.1 What are Enzymes?

Question 1

What are enzymes?

Answer 1

A type of catalyst made by living organisms

Question 2

Explain how speeding up a reaction by raising the temperature can also have a negative effect.

Answer 2

It would speed up the useful reactions but also the unwanted ones too

Question 3

What do enzymes do?

Answer 3

Enzymes reduce the need for high temperatures; they act as biological catalysts

Question 4

What type of chemical reactions do we use enzymes for?

Answer 4

We only have enzymes to speed up the useful chemical reactions in the body

Question 5

What is an example of something that enzymes are used to speed up in plants?

Answer 5

Photosynthesis

Question 6

What are 3 disadvantages of raising temperatures in order to speed up reactions?

Answer 6

• Requires a lot of energy
• High temperatures can damage cells
• Also speed up non-useful reactions

Question 7

What is a catalyst?

Answer 7

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

Question 8

What is another name for enzymes?

Answer 8

Biological catalysts

Question 9

What are enzymes made up of?

Answer 9

Long chains of amino acids

Question 10

How are different enzymes unique?

Answer 10

The long chains of amino acids fold up into different shapes, making different enzymes and therefore catalyse particular chemical reactions

Question 11

What is the substrate?

Answer 11

The molecule changed in the reaction

Question 12

What is the active site?

Answer 12

The part where it joins on to its substrate to catalyse the reaction - it has a unique shape complementary to the substrates

Question 13

Do enzymes change or stay the same after reactions?

Answer 13

Stay unchanged

Question 14

Describe the lock and key model

Answer 14

Scientists thought that the substrate had to fit perfectly into the active site

Question 15

Describe the induced fit model

Answer 15

The enzyme actually changes shape slightly as it binds to the substrate

Question 16

Describe how increased temperature increases the rate of enzyme-catalysed reactions

Answer 16

Like with any reaction, a higher temperature increases the rate at first, the enzymes and substrate have more energy, so they move about more and are more likely to collide and form enzyme-substrate complexes. But 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 wont fit any more. The enzyme is said to be denatured. All enzymes have an optimum temperature that they work best at

Question 17

Describe how different pH affects the rate of enzyme-catalysed reactions

Answer 17

If it’s too high or too low, the pH interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzymes. All enzymes have an optimum pH that they work best at. It’s often neutral pH 7, but not always

Question 18

Describe how substrate concentration affects the rate of enzyme-catalysed reactions

Answer 18

Substrate concentration also affects the rate of reaction - the higher the substrate concentration, the faster the reaction. This is because it’s more likely that the enzyme will meet up and react with a substrate molecule. This is only true up to a point though. After that, there are so many substrate molecules that the enzymes have about as much as they can cope with (all the active sites are full), and adding more makes no difference

Question 19

What is the name of the special region of an enzyme that binds to the substrate?

Answer 19

Active site