Chapter 3.2: Energy, Catalysis, and Biosynthesis - BMEN 240

What is the primary function of activated carriers in metabolism?

They shuttle energy by coupling catabolism (energy release) to anabolism (biosynthesis).

What is the net equation for an ATP-driven condensation reaction?

A-OH + B-H + ATP → A-B + ADP + P + H+.

How much energy does the standard hydrolysis of ATP yield?

Between 11 and 13 kcal/mole (46 to 54 kJ/mole).

Why is the terminal phosphate bond of ATP high energy?

Removing it relieves charge repulsion and produces resonance-stabilized inorganic phosphate.

Give an example of a biosynthetic reaction driven by ATP hydrolysis.

Synthesis of glutamine from glutamic acid and ammonia.

What high-energy unit do NADH and NADPH carry?

A hydride ion (H⁻), composed of two high-energy electrons and one proton.

What is the primary cellular role of NADPH?

It acts as a reducing agent in anabolic (biosynthetic) pathways.

What is the primary cellular role of NAD+?

It acts as an oxidizing agent in catabolic (breakdown) pathways.

Why is NADPH a stronger electron donor than NADH in cells?

Cells maintain a high concentration ratio of reduced NADPH to oxidized NADP+.

Which biosynthetic process relies on NADPH in its final stage?

Cholesterol biosynthesis.

What group does Acetyl Coenzyme A (CoA) carry and via what bond?

Carries an acetyl group attached via a high-energy thioester bond.

What group does carboxylated biotin transfer?

A carboxyl group.

Which enzyme uses carboxylated biotin to make oxaloacetate?

Pyruvate carboxylase.

What group does ATP carry and transfer?

A phosphate group.

How do condensation and hydrolysis reactions differ regarding water and energy?

Condensation expels water and requires energy; hydrolysis consumes water and releases energy.

What alternative ATP hydrolysis route yields about double the energy (~26 kcal/mole)?

Hydrolysis of ATP into AMP and pyrophosphate (PPi), followed by PPi hydrolysis.

How is nucleic acid (RNA/DNA) synthesis energized?

Driven by multi-step nucleoside triphosphate hydrolysis releasing pyrophosphate.