74 WJEC Biology AS Level - Marianne Izen - 2nd Edition (1.4 Enzymes And Biological Reactions)

Question 1

What does the term metabolism refer to?

Answer 1

The term metabolism refers to all the reactions of the body.

Question 2

What are metabolic pathways?

Answer 2

Reactions occur in sequences called metabolic pathways.

Question 3

What are the type of reactions that occur in metabolic pathways?

Answer 3

1. Anabolic reactions
2. Catabolic reactions

Question 4

What are anabolic reactions?

Answer 4

Anabolic reactions means building up molecules, e.g. protein synthesis

Question 5

What are catabolic reactions?

Answer 5

Catabolic reactions means breaking molecules down, e.g. digestion.

Question 6

What controls metabolic pathways?

Answer 6

Metabolic pathways are controlled by enzymes.

Question 7

In metabolic pathways, what happens to the products of one reaction?

Answer 7

The products of one enzyme-controlled reaction become reactants in the next.

Question 8

What are enzymes?

Answer 8

Enzymes are globular proteins that are catalysts.

Question 9

Why are enzymes called biological catalysts?

Answer 9

They are called ‘biological’ catalysts because they are made by living cells.

Question 10

Do enzymes and chemical catalysts share properties?
Explain.

Answer 10

Yes, enzymes and chemical catalysts share properties in the reactions they catalyse. These are:

They speed up reactions.
They are not used up.
They are not changed.
They have a high turn-over number

Question 11

What do you mean when you say that enzymes have a high turnover number?

Answer 11

It means they catalyse many reactions per second.

Question 12

What type of reactions do enzymes catalyse?

Answer 12

Enzymes only catalyse reactions that:

1. are energetically favourable
2. would happen anyway.

Question 13

If enzymes only catalyse reactions that would happen anyway, why do you need them?

Answer 13

Without enzymes, reactions in cells would be too slow to be compatible with life.

Question 14

What level of structure do enzymes have?

Answer 14

Enzymes are proteins with tertiary structure

Question 15

What is the tertiary structure of enzymes?

Answer 15

The protein chain folds into a spherical or globular shape.

The hydrophilic R groups are on the outside of the molecule, making enzymes soluble.

Question 16

What is the primary structure of an enzyme.

Answer 16

Each enzyme has a particular sequence of amino acids

Question 17

What determines the bonds the amino acids make with each other in an enzyme?

Answer 17

The elements in the R groups determine the bonds the amino acids make with each other.

Question 18

What are type of bonds seen in enzymes?

Answer 18

1. hydrogen bonds
2. disulphide bridges
3. ionic bonds

Question 19

What is the function of the bonds seen in enzymes?

Answer 19

They hold the enzyme molecule in its tertiary form.

Question 20

What is the active site of an enzyme?

Answer 20

A small area with a specific 3D shape is the active site.

Question 21

What is the importance of the active site?

Answer 21

It gives the enzyme many of its properties.

Question 22

Draw the structure of an enzyme

Answer 22

Question 23

Metabolism (Key-Term)

Answer 23

All the organism’s chemical processes, comprising anabolic and catabolic pathways.

Question 24

Metabolic pathway (Key-Term)

Answer 24

A sequence of enzyme-controlled reactions in which a product of one reaction is a reactant in the next.

Question 25

Enzyme (Key-Term)

Answer 25

A biological catalyst; a protein made by cells that alters the rate of a chemical reaction without being used up by the reaction.

Question 26

Catalyst (Key-Term)

Answer 26

An atom or molecule that alters the rate of a chemical reaction without taking part in the reaction or being changed by it.

Question 27

Active site (Key-Term)

Answer 27

The specific three- dimensional site on an enzyme molecule to which the substrate binds by weak chemical bonds.

Question 28

Do all chemical bonds have the same strength?
Explain.

Answer 28

No, chemical bonds vary in strength, depending on the atoms that they join and on their chemical environment.

Hydrogen bonds are weak but if there are many of them, they have a significant binding effect.

Ionic and covalent bonds, such as the disulphide bond, are stronger than hydrogen bonds.