More stuff that i need to remember

Question 1

Allosteric Regulation

Answer 1

Enzymes are regulated by binding of activators or inhibitors at sites other than the active site.
This causes a conformational change that affects activity.

Question 2

Covalent Modification

Answer 2

Enzyme activity is regulated by reversible addition or removal of chemical groups, such as phosphorylation, methylation, or acetylation.

Question 3

Gene Expression (Transcriptional Regulation)

Answer 3

Regulates the amount of enzyme produced by controlling transcription of the gene encoding the enzyme.

Question 4

how exergonic reactions are manipulated

Answer 4

If a reaction has a slightly positive ΔG°′ (i.e. not spontaneous under standard conditions), it can still proceed in the forward direction if:

The concentration of reactants increases, or

The concentration of products decreases (e.g. products are rapidly used in the next step)

This is how metabolic pathways “pull” or “push” reactions forward — by manipulating concentrations.

Question 5

Why is pyruvate converted into acetyl-CoA before entering the TCA cycle? (2 marks)

Answer 5

Activation for Entry into the TCA Cycle:
Pyruvate is converted to acetyl-CoA to link glycolysis to the TCA cycle, enabling the carbon atoms from glucose to enter the cycle for complete oxidation.

High-Energy Thioester Bond Formation:
The conversion forms a high-energy thioester bond in acetyl-CoA, which activates the acetyl group for condensation with oxaloacetate in the citrate synthase reaction, driving the first step of the cycle forward.

Question 6

why is ATP called the energy currency of the cell

Answer 6

ATP is called the “energy currency of the cell” because it stores and transfers energy in a form that cells can readily use to power biological processes such as muscle contraction, active transport, and biosynthesis.

Question 7

Why ATP is a good allosteric regulator of metabolic pathways (2 marks)

Answer 7

Reflects the cell’s energy status:
ATP levels indicate how much energy is available. When ATP is high, the cell has enough energy, so ATP can inhibit catabolic pathways (like glycolysis) to prevent unnecessary energy production.

Rapid, reversible control:
ATP can bind allosterically to key metabolic enzymes (e.g. phosphofructokinase-1) and cause conformational changes that quickly adjust metabolic activity, allowing the cell to respond efficiently to changing energy needs.