DD - Intro to Cell Metabolism 1

Question 1

What are the 2 type of metabolic pathways?

Answer 1

Catabolic
- Release energy
- Involved in the breakdown of molecules
- Anabolic
* - Require energy
- Involved in the synthesis of complex molecules from simpler molecules

Question 2

What 2 functions does the Oxidative Catabolism of Glucose involve?

Answer 2

1. The production of ‘free energy’ in the form of ATP
2. The production of intermediates from glycolysis and the TCA cycle provides material for other metabolic pathways

Question 3

How do we characterise a Metabolic Pathway?

Answer 3

Using the change in Gibbs free energy, individual steps of the pathway are characterised

Question 4

What is the difference between ΔG°´ and ΔG°

Answer 4

ΔG°´- is the change in Gibbs free energy at pH 7.0 under standard conditions
ΔG°- is the change in Gibbs free energy at pH 0 (1 M [H+]) under standard conditions

Question 5

What happens if ΔG°´ is negative?

Answer 5

Free energy is released - EXERGONIC

Question 6

What happens if ΔG°´ is positive?

Answer 6

Free energy is absorbed - ENDERGONIC

Question 7

What is ΔG dependent on?

Answer 7

ΔG = ΔG°´+ RT lnQ
1. A constant term whose value depends only on the reaction taking place
2. A variable term that deoends on the concentration of reactants and products

Question 8

What is defined by Le Chatelier’s Principle?

Answer 8

Any deviation from equilibrium stimulates a process that tends to restore the system to equilibrium

Question 9

In metabolic pathways, are ΔG values additive?

Answer 9

Yes- Any one reaction can have a positive ΔG but if overall ΔG is negative, the pathway proceeds

Question 10

What are the main features of metabolic pathways? (7)

Answer 10

1. Metabolic pathways are irreversible
2. Every pathway has a first committed step
3. Catabolic and anabolic pathways differ
4. Feedback inhibition
5. In eukaryotes, metabolic pathways occur in specific cellular locations
6. Pathways are controlled by switching on/off the gene for the first enzyme
7. Enzymes act in groups or as multi-enzyme complexes

Question 11

What are the 2 main ways to regulate metabolic pathways?

Answer 11

1. Gene regulation
- Slower
- Can greatly increase enzyme product
2. End-product feedback inhibition
- Faster
- Depends on usage of end product