Unit 1.6 Metabolic Pathways

Question 1

What is cell metabolism

Answer 1

The product of all the biochemical reactions that take place in a living cell

Question 2

What are metabolic pathways

Answer 2

Integrated & controlled pathways of enzyme-catalysed reactions within a cell

Question 3

The 2 types of metabolic pathways

Answer 3

Catabolic reactions & Anabolic reactions

Question 4

What do catabolic reactions do

Answer 4

Break down large molecules into smaller molecules and release energy

Question 5

What do anabolic reactions do

Answer 5

Build up large molecules from small molecules and requires energy

Question 6

2 examples of catabolic reactions

Answer 6

1- Aerobic respiration
2- Breakdown of starch by amylase: starch —> maltose

Question 7

2 examples of anabolic reactions

Answer 7

1- protein synthesis
2- Synthesis of starch by phosphorylase: glucose-1-phosphate —> starch

Question 8

What are the 2 types of steps a metabolic pathway could have

Answer 8

Reversible & irreversible

Question 9

What type of pathway can bypass steps

Answer 9

Alternative pathways

Question 10

What happens in reversible reaction

Answer 10

The substrate is converted into the product as long as the concentration of the reactant (substrate) is relatively higher than the product

Question 11

What happens if the concentration of the reactant decreases in a reversible reaction

Answer 11

The reaction will proceed in the opposite direction

Question 12

What do enzymes work to keep in a reversible reaction

Answer 12

An equilibrium- to maintain a balance of the starting reactants & products

Question 13

What happens in the irreversible steps of a metabolic pathway

Answer 13

Once the substrate has turned into a product it cannot change back to a substrate

Question 14

What do alternative routes in metabolic pathways allow

Answer 14

Certain steps in a pathway to be bypassed

Question 15

What is metabolic rate

Answer 15

The quantity of energy consumed by an organism per unit of time

Question 16

What can metabolic rate be measured by

Answer 16

Oxygen consumption, CO2 production & energy production in the form of heat

Question 17

What are metabolic pathways controlled by

Answer 17

The presence or absence of particular enzymes
& the regulation of the rate of reaction of key enzymes

Question 18

What are enzymes

Answer 18

Biological catalysts that speed up the rate of a reaction but remain unchanged after the reaction has taken place

Question 19

What is activation energy

Answer 19

The energy needed to either make or break chemical bonds in the reactant chemicals (enzyme substrates)

Question 20

What are reactant chemicals

Answer 20

Enzymes / substrates

Question 21

How does an enzyme speed up a reaction

Answer 21

By lowering the activation energy

Question 22

What is an active site

Answer 22

A region on the surface of an enzyme where the substrate binds

Question 23

What is enzyme specificity

Answer 23

The shape of the active site means only a substrate with a complementary shape can bind to the active site

Question 24

What does it mean if a substrate has a higher affinity for an enzyme

Answer 24

The substrate is specific/complementary to the enzyme

Question 25

What is induced fit

Answer 25

When the active site on the enzyme changes shape to better fit the substrate after the substrate binds

Question 26

What does induced fit increase the chance of

Answer 26

A reaction taking place

Question 27

How does induced fit increase the chance of a reaction

Answer 27

By ensuring the active site comes into very close contact with the molecules of the substrate

Question 28

What does induced fit cause to happen after the reaction takes place

Answer 28

The subsequent products now have a low affinity for the active site allowing them to leave the active site

Question 29

What happens once enzymes have absorbed sufficient energy

Answer 29

Chemical bonds break & the reactants reach an unstable transition state

Question 30

What happens as you increase substrate concentration

Answer 30

More enzyme/substrate complexes can form- this speeds up the rate of reaction

Question 31

What happens once the enzyme is no longer in excess

Answer 31

The number of complexes is at a maximum, the rate of reaction levels off & remains constant no matter how much more substrate is added

Question 32

How can you increase the rate of reaction once substrate concentration is at its maximum

Answer 32

Increase enzyme concentration

Question 33

What are enzyme inhibitors

Answer 33

Chemicals that slow down or stop an enzyme-controlled reaction

Question 34

2 types of inhibitors

Answer 34

Competitive & Non-competitive

Question 35

What do competitive inhibitors do

Answer 35

Bind at the active site, so are competing with the substrate. This prevents substrate from binding

Question 36

Can competitive inhibition be reversed- if so, how?

Answer 36

Yes, by increasing substrate concentration

Question 37

What do non-competitive inhibitors do

Answer 37

Bind at the enzyme- not at the active site.
This causes the shape of active site to be altered & substrate molecules can no longer bind to the active site

Question 38

Can non-competitive inhibition be reversed

Answer 38

No

Question 39

When does feedback inhibition occur

Answer 39

When the end product in the metabolic pathway reaches a critical condition. It then inhibits an earlier enzyme, blocking the pathway & preventing further synthesis of the end product

Question 40

What effect will increasing the substrate concentration have on a normal enzyme reaction

Answer 40

Increase the reaction

Question 41

What effect will increasing the substrate concentration have on a reaction with a competitive inhibitor present

Answer 41

Increase the reaction

Question 42

What effect will increasing the substrate concentration have on a reaction with a non-competitive inhibitor present

Answer 42

No effect