U1: 6- Metabolic Pathways

Question 1

What name is given to the thousands of biochemical reactions that occur in living cells?

Answer 1

Metabolism

Question 2

The quantity of energy consumed by an organism per unit time is a measure of what rate?

Answer 2

Metabolic rate

Question 3

Name two types of metabolic pathway.

Answer 3

Anabolic pathway and catabolic pathway

Question 4

Which type of metabolic pathway involves the breakdown of complex molecules into simpler ones?

Answer 4

Catabolic

Question 5

Which type of metabolic pathway involves the build-up of complex molecules from simpler ones?

Answer 5

Anabolic

Question 6

Which type of metabolic pathway releases energy as it is breaking complex molecules down?

Answer 6

Catabolic

Question 7

Which type of metabolic pathway requires energy as it builds up small molecules to complex molecules?

Answer 7

Anabolic

Question 8

In a metabolic pathway what do the two opposing arrows mean?

Answer 8

The reaction is reversible

Question 9

Metabolic reactions sometimes have places where steps can be bypassed, what are these pathways known as?

Answer 9

Alternative routes

Question 10

Give three properties of a catalyst.

Answer 10

• lowers the activation energy
• remains unchanged at the end
• increases the rate of reaction

Question 11

What name is given to biological catalysts?

Answer 11

Enzymes

Question 12

What state is reached when two reactants have bonds broken and they are in a position that is unstable and ready to form a product?

Answer 12

Transition state

Question 13

What substance are enzymes made from?

Answer 13

Protein

Question 14

What name is given to the area on an enzyme that meets with the substrate?

Answer 14

Active site

Question 15

What determines the shape of the active site?

Answer 15

The sequence of amino acids in the polypeptide that makes up the enzyme molecule

Question 16

Give the word that is used to describe the fact that one enzyme fits one substrate.

Answer 16

Specific

Question 17

Give the term that is used to describe the fact that the active site has a strong attraction for the substrate.

Answer 17

High affinity

Question 18

Once the enzyme has broken the substrate down/built it up and formed the product, how is the attraction for the active site described?

Answer 18

Low affinity

Question 19

In order for the enzyme’s active site to fit the substrate more closely, the shape of the active site and enzyme change slightly. What is this called?

Answer 19

Induced fit

Question 20

Fill in the missing gap: The shape of the active site determines the … of reactants.

Answer 20

Orientation

Question 21

In an enzyme controlled reaction the reaction rate will increase as the substrate concentration increases up until a certain point. After that the rate of reaction does not increase, why is this?

Answer 21

Because all of the active sites on the enzyme are occupied

Question 22

What can be done to increase the rate of an enzyme controlled reaction once all of the active sites on the enzyme are occupied and substrate has already been increased?

Answer 22

Add more of the enzyme to the reaction

Question 23

What name is given to a substance that decreases the rate of an enzyme controlled reaction?

Answer 23

An inhibitor

Question 24

Name two types of inhibitor.

Answer 24

Competitive inhibitor and non-competitive inhibitor

Question 25

Which inhibitor binds to the active site and competes with the substrate in an enzyme controlled reaction?

Answer 25

Competitive inhibitor

Question 26

Why is the competitive inhibitor able to join to the active site of an enzyme?

Answer 26

Because it has a similar shape to the substrate

Question 27

What happens to the rate of reaction in an enzyme controlled reaction that is affected by a competitive inhibitor?

Answer 27

Decreases the rate of reaction but doesn’t stop it altogether because the substrate can still bind sometimes

Question 28

How could the effects of a competitive inhibitor be reversed?

Answer 28

Increase the substrate concentration

Question 29

Where does a non-competitive inhibitor bind to?

Answer 29

An allosteric site (site away from the active site)

Question 30

What does a non-competitive inhibitor do to the shape of an enzyme active site?

Answer 30

Changes the shape of the active site

Question 31

Why does a reaction affected by a non-competitive inhibitor stop altogether?

Answer 31

Because the shape of the active site has changed permanently and it no longer recognises the substrate

Question 32

When an end product is made in a metabolic pathway some of the product goes back and inhibits an enzyme at the start of the pathway, what is this called?

Answer 32

End product inhibition