Key Area 4 - Proteins

Question 1

What is an enzyme?

Answer 1

A biological catalyst that is made by all living cells

Question 2

What do enzymes do?

Answer 2

They speed up chemical reactions and are unchanged in the process.

Question 3

How would life be affected without the help of enzymes?

Answer 3

Chemical reactions would occur so slowly that life would be impossible.

Question 4

What are the key characteristics of enzymes?

Answer 4

• They are made in all living cells
• They speed up cellular reactions
• They are unchanged in the process so can be reused
• They are protein molecules

Question 5

What are enzymes?

Answer 5

Biological catalyst produced by all living cells: they speed up chemical reactions without taking part themselves
(e.g. Amylase breaks down starch to maltose - SAM)

Question 6

What are hormones?

Answer 6

Chemical messengers transported in the blood from endocrine glands to target tissues.
(e.g. Insulin controls blood glucose level.)

Question 7

What are antibodies?

Answer 7

Provides defence against specific bacteria and viruses. They bind to bacteria and viruses to allow white blood cells to recognise and destroy them.
(e.g. Immunoglobulins (IgA) IgA is found in breast milk and helps protect the new born baby from infections)

Question 8

What is a structural protein?

Answer 8

They provide strength and support for cell structures.

e.g. Structural proteins within the cell membrane & Keratin in nails and hair.

Question 9

What are receptors?

Answer 9

Allow cells to recognise specific chemical signals.

e.g. Liver cells have receptors for insulin.

Question 10

Each enzyme has its own unique protein structure and overall shape which is designed to match and complement what?

Answer 10

The substance (substrate) on which it works

Question 11

What is the special region on the surface of enzyme molecules called and what does it do?

Answer 11

The active site, where they bind to their substrate.

Question 12

What is the active site unique to?

Answer 12

It is unique and complementary to specific substrates and don’t act on other types.

Question 13

What is a summary of enzyme reactions?

Answer 13

Substrate(s) —>Enzyme —>Products

Question 14

What is a substrate?

Answer 14

A particular chemical substance(s) on which a specific enzyme works.

Question 15

What is a product?

Answer 15

Substance(s) formed by the action of an enzyme in its substrate(s).

Question 16

Why is an enzyme said to be specific?

Answer 16

Because it can on,y work on one type of substrate.

Question 17

What is the active site of an enzyme?

Answer 17

The place on its surface that is complementary in shape to its substrate

Question 18

What are the two main types of enzyme catalysed reactions?

Answer 18

Degradation reactions and synthesis reactions

Question 19

What is a degradation reaction?

Answer 19

When one substrate is broken down to form more than one product.

Question 20

What is a synthesis reaction?

Answer 20

Several substrate molecules are bound together to form one product.

Question 21

Give two examples of degradation reactions?

Answer 21

Hydrogen peroxide —> Catalase —> Oxygen + water
(HPCOW)

Starch —> Amylase —> maltose
(SAM)

Question 22

Give an example of a synthesis reaction:

Answer 22

Glucose-1-phosphate —> phosphorylase —> starch

Lots of them). (G1PPS

Question 23

What happens to enzymes when they are too cold?

Answer 23

They move slowly so the reaction takes longer to complete

Question 24

What happens when an enzyme is too hot?

Answer 24

It’s shape changes and the rate of reaction decreases.

Question 25

When do enzymes work at their fastest rate?

Answer 25

Around 40 degrees for mammalian enzymes, they facilitate the breakdown/build-up of the substrate(s) into product(s) in the shortest time.

Question 26

What is the temperature at which an enzyme works fastest called?

Answer 26

Their optimum temperature

Question 27

What happens when the bonds in a protein are heated?

Answer 27

The proteins shape begins to break and it starts to unravel.

Question 28

What happens for the enzyme to become denatured?

Answer 28

The protein loses the shape of its active site and can no longer bind to its substrate

Question 29

What happens once the proteins structure has been changed by heating?

Answer 29

The effect is permanent and irreversible, the enzyme can no longer bind to its substrate as they are no longer complementary in shape, so it can no longer catalyse the reaction.

Question 30

What is the optimum pH for an enzyme?

Answer 30

One where it works the fastest.

Question 31

Most enzymes function within what?

Answer 31

A working range of pH values.

Question 32

What happens outside the working range?

Answer 32

The extremes of pH may break the hydrogen bonds between the amino acids of the enzyme, permanently altering the shape of the active site. The enzyme becomes denatured.

Question 33

What is the optimum?

Answer 33

A condition of a factor at which an enzyme works best