Integration and Control of Metabolism

Question 1

What are the two aspects of metabolism?

Define them

Answer 1

Catabolism - breaks down complex molecules, yields ATP

Anabolism - biosynthesis of complex molecules, uses ATP

Question 2

What is NADP/H?

Answer 2

Nicotinamide Adenine Dinucleotide Phosphate

The major electron donor in biosynthetic pathways

Question 3

What are the 3 key junctional points in glucose metabolism

Answer 3

Glucose
Glucose-6-phosphate
Pyruvate
Acetyl CoA

Question 4

How are the complex network of metabolic reactions in a cell regulated?

Answer 4

Cells are self-regulating

Close control of ATP, NADPH, metabolites

Question 5

3 cell states when the metabolic requirements change

Answer 5

at rest
undergoing growth and development
in a disease state

Question 6

What are intrinsic controls?

Give 3 examples

Answer 6

Controls within the cell
Availability of substrate
Regulation of enzyme activity (feedback mechanisms)
Differential expression of enzyme isoforms e.g lactate in liver

Question 7

What are extrinsic controls?

Give 3 examples of how they affect metabolism

Answer 7

Hormones and signals outside the cell
Substrate uptake e.g. insulin/glucagon
Modulation of enzyme activity through extracellular signals
Extracellular modulation of enzyme expression

Question 8

The idea of a rate determining step

Where is it usually found? Why?

Answer 8

The pathway can only be as fast as the slowest step allows, therefore only one step needs to be controlled
Found at the beginning of the pathway, reduces the waste of substrates

Question 9

How are RDS enzymes controlled? x3

Answer 9

1 - Feedback inhibition (negative feedback)
2 - allosteric effects, some enymes undergo huge conformational change, modulates activity
3 - covalent modification, phosphorylation

Question 10

What are the 3 irreversible steps in glycolysis?

Answer 10

hexokinase
phosphofructokinase
pyruvate kinase