Metabolic Pathways

Question 1

What are metabolic pathways? (2)

Answer 1

-Integrated and controlled pathways of enzyme-catalysed reactions within a cell.
- can be described as chemical reactions that start with a substrate and finish with an end product

Question 2

What types of steps can metabolic pathways have?

Answer 2

Reversible steps, irreversible steps, and alternative routes.

Question 3

What are the two main types of reactions in metabolic pathways?

Answer 3

Anabolic and catabolic reactions.

Question 4

What do anabolic reactions do?

Answer 4

Build up large molecules from small molecules and require energy. (biosynthetic reactions)

Question 5

What do catabolic reactions do?

Answer 5

Break down large molecules into smaller molecules and release energy.
(Breakdown reactions)

Question 6

Where are protein pores, pumps, and enzymes found?

Answer 6

Embedded in membranes.

Question 7

What are protein pumps, what do they do?

Answer 7

They act as carrier molecules and recognise specific ions and transfer them across the cell membrane.

Question 8

What are protein pores? What do they do?

Answer 8

Pores are contained Inside transport molecules, which allow ions of a particular size to pass through the membrane.

Question 9

What is the role of enzymes in metabolic pathways?

Answer 9

Enzymes act as catalysts that speed up chemical reactions in metabolic pathways.

Question 10

Are Enzymes consumed in the reactions they catalyse?

Answer 10

Enzymes are not consumed and can be reused.

Question 11

The specific region of an enzyme where substrate molecules bind is called the ______.

Answer 11

active site

Question 12

What is feedback inhibition? (3)

Answer 12

-Feedback inhibition occurs when the end product in a metabolic pathway reaches a critical concentration
-where the end product of a metabolic pathway binds to an enzyme at the start of the pathway.
-This process stops the metabolic pathway and so prevents further synthesis of the end product till the concentration of end products decreases.

Question 13

Which 4 factors can affect enzyme activity?

Answer 13

Temperature
pH
substrate concentration
enzyme concentration

Question 14

What is the difference between competitive and non-competitive inhibition?

Answer 14

Competitive inhibition occurs when an inhibitor competes with the substrate for the active site, while non-competitive inhibition occurs when an inhibitor binds to a different part of the enzyme and changes the active site shape.

Question 15

True or False: Enzymes lower the activation energy required for a reaction to proceed.

Answer 15

True

Question 16

What is the role of enzymes in metabolic pathways?(2)

Answer 16

Enzymes regulate and control metabolic pathways to prevent the build-up of unnecessary end products.

Enzymes can control the pathway by their presence or absence, as well as by regulating the reaction rates.

Question 17

What is an active site? (4)

Answer 17

-The active site is the region on an enzyme where substrates bind and reactions occur.
-It can change shape slightly when the substrate is bound.
- it has a high affinity to the substrate
-It is specific to the substrate and facilitates the reaction.

Question 18

Induced fit

Answer 18

Induced fit is when the active site of the enzyme changes shape slightly to fit the substrate better after binding.

Question 19

What happens to the binding affinity of products to the enzyme after the reaction?

Answer 19

Products have a low affinity to the enzyme and are released after the reaction.

Question 20

How do enzymes affect the activation energy of a reaction?

Answer 20

Enzymes lower the activation energy needed for a reaction to occur, Which makes the metabolic pathway more efficient.

Question 21

What drives the direction of reversible metabolic reactions?

Answer 21

The presence of a substrate or removal of a product drives reversible metabolic reactions in a particular direction.

Question 22

What is a factor that affects the rate of enzyme reaction?

Answer 22

Substrate concentration

Question 23

What happens to the enzyme reaction rate as substrate concentration increases?

Answer 23

It increases until all active sites are occupied

Question 24

What occurs when all active sites of an enzyme are occupied?

Answer 24

The enzyme is saturated. At the saturation point adding more substrates makes no difference to the reaction rate.

Question 25

What is the role of inhibitors in metabolic pathways?

Answer 25

Inhibitors can stop an enzyme from binding to its substrate, controlling the progress of a metabolic pathway.

Question 26

Name the three types of inhibition.

Answer 26

-Competitive inhibition
-Non-competitive inhibition
- Feedback inhibition

Question 27

What is competitive inhibition? (2)

Answer 27

A type of inhibition where an inhibitor competes with the substrate for the active site of an enzyme.

This reduces the enzyme’s ability to bind to its substrate.

Question 28

What is an enzyme?

Answer 28

An enzymes are biological catalysts.
They speed up chemical reactions by lowering the activation energy.

Question 29

What is affinity in the context of enzymes?

Answer 29

Affinity refers to the chemical attraction between the substrate and the active site of the enzyme.

Question 30

What determines the orientation of reactants in an enzymatic reaction?

Answer 30

The shape of the active site.