2.1 Metabolic Pathways and their control

Question 1

Define ‘metabolism of a cell’

Answer 1

Sum total of all biochemical reactions that occur within a cell

Question 2

What are the three types of steps in a metabolic pathway/

Answer 2

Reversible
Irreversible
Alternative

Question 3

What is an advantage of having reversible steps in a metabolic pathway?

Answer 3

Allows processes to be kept under precise control

Question 4

What is an advantage to having alternative steps in a metabolic pathway?

Answer 4

Allows an end product still to be reached if a specific enzyme/ substrate is unavailable

Question 5

Describe an ‘Anabolic’ pathway

Answer 5

Anabolic

• Synthesis/Build up of a larger molecule from smaller molecules
• Requires Energy

Question 6

Give an example of an anabolic process

Answer 6

Photosynthesis

Question 7

Describe a ‘Catabolic’ pathway

Answer 7

• Break down of larger molecules into smaller molecules

- Releases Energy

Question 8

Give an example of a catabolic process

Answer 8

Aerobic Respiration

Question 9

What is it called when an anabolic pathway becomes interdependent on a catabolic pathway?

Answer 9

Integrated Metabolic Pathway

Question 10

Describe the function of a membrane?

Answer 10

Controls the entry and exit of materials in a cell

Question 11

What are the inner folds of a membrane called?

Answer 11

Cristae

Question 12

What are the types of proteins found in a cell membrane?

Answer 12

• Protein Pump
• Channel forming protein
• Enzyme

Question 13

Describe the phospholipid bilayer

Answer 13

• Double layer of phospholipids which are in CONSTANT MOTION
• Keeps the structure fluid but stable
• Contains proteins, which are attached by weak chemical bonds

Question 14

Describe the structure of a phospholipid

Answer 14

Hydrophilic head (water loving)
Hydrophobic tail(water hating)

Question 15

What is the function of a protein pump?

Answer 15

• Move molecules AGAINST A CONCENTRATION GRADIENT

- Requires Energy

Question 16

Give an example of a protein pump?

Answer 16

Sodium Potassium Pump(Potassium In, Sodium Out)

Question 17

What is the function of a channel forming protein?

Answer 17

• Form channels for large molecules to diffuse through
• No ATP required
• Passive Process

Question 18

What is the function of a membrane in compartmentalisation

Answer 18

Divide up cells into regions which have specialised functions and are required for specific metabolic steps

Question 19

Give an example of a double membraned organelle

Answer 19

Nucleus

Question 20

Give an example of a single membraned organelle

Answer 20

Endoplasmic Reticulum

Question 21

How are metabolic pathways controlled at gene expression level?

Answer 21

• When a gene is expressed a protein is produced
• Proteins make up enzymes
• Enzymes are responsible for controlling steps in metabolic pathways

Question 22

What will result in a block to a metabolic pathway?

Answer 22

Mutations

Question 23

What is the ‘activation energy’

Answer 23

The minimum energy required to initiate a chemical reaction

Question 24

How do enzymes speed up the rate of a chemical reaction?

Answer 24

Speed up the reaction but are not used up because they lower the activation energy

Question 25

What does ‘Affinity’ stand for?

Answer 25

Affinity is the strength of attraction between two molecules

Question 26

Do substrates have high or low affinity for the active site of an enzyme?

Answer 26

High

Question 27

Do products have high or low affinity for the active site of an enzyme?

Answer 27

Low

Question 28

How does substrate concentration effect reversible reactions?

Answer 28

Reversible reactions can go either way depending on the relative concentrations of substrate/products

Question 29

Describe how ‘orientation’ affects enzymes and substrates

Answer 29

The substrate has to be at the right orientation in order to fit into the active site

Question 30

Explain the process of ‘Induced Fit’

Answer 30

Induced fit is the process by which an enzyme molds its active site to fit more tightly around a substrate. It ensures the substrate is pulled in close and increases the chance of a reaction occurring.

Question 31

Describe a multi enzyme complex

Answer 31

A multi enzyme complex is a collection of enzymes found together on a membrane