Metabolism essentials

Question 1

How to study metabolic reactions?

Answer 1

2 Methods:

1. In-vitro: e.g. Harden/Young.
2. In vivo

Question 2

Adv + Disadvs to in-vitro approach?

Answer 2

+ :
- Important for studying e.g. lysis + homogenisation
- Direct results
- Defined controlled conditions

• :
• No knowledge of compartmentation in cell.
• May degrade key components cell normally uses
• Conditions may not be accurate to real cell conditions.

Question 3

Adv + Disadvs to in-vivo approach?

Answer 3

+ :
- In cellular environment
- Can do cellular assays etc.

• :
• Harder to get quantitative data.
• Many variables to consider compared to in vitro.

Question 4

Why do we need metabolic pathways?

Answer 4

Energy is conserved so brings reactions under control via regulation + stoppages.

Question 5

6 Key reactions in metabolism?

Answer 5

1. Redox: transfer e-
2. Ligation: form covalent bonds (needs ATP)
3. Isomerisation: rearranging atoms to form isomer.
4. Group transfer: transfer functional group between molecules
5. Hydrolysis: water cleavage of bonds (opposite to condensation)
6. Adding/Removing function groups: add/remove double bonds.

Question 6

What are metabolic crossroads?

Answer 6

Most pathways link via common intermediates.

Question 7

What are cofactors ?

Answer 7

Stable molecules that add to enzymes to enhance metabolic activity.

Question 8

Examples of common cofactors in metabolism?

Answer 8

Energy carrier: ATP
Electron carriers: NAD+, FAD+ and NADPH
2-carbon carrier: CoA

Question 9

What are the 2 main limitations to metabolic pathways?

Answer 9

1. Limited no of types of types.
2. Limited no of cofactors.

Question 10

What are NAD and FAD?

Answer 10

NAD = nicotineamide adenine dinucleotide
-> from Niacin (vit B3)
FAD = flavin adenine dinucleotide
- from Riboflavin (vit B2)

Question 11

What is catabolism and stages?

Answer 11

Catabolism = breaking down to make energy.

1. Large molecules -> small
2. Products of first stage -> Acetyl CoA (minimal ATP made).
3. Acetyl of Acetyl-CoA -> CO2 (most ATP made here).

Question 12

What is anabolism?

Answer 12

The building up of molecules using energy.

NOT JUST REVERSAL OF CATABOLISM.

Question 13

What is special about regulatory points ?

Answer 13

Large negative delta G. (doesn’t tell anything about speed of pathway).

Question 14

What does large delta G mean in terms of energy?

Answer 14

Energy released.
Large K so reaction is favoured.