🔴 Thermodynamics, Bioenergetics & Biochemical Oxidation

What does thermodynamics study in biological systems?

The energy changes that accompany chemical reactions and whether reactions are energetically favorable.

What is the Gibbs free energy equation?

ΔG = ΔH − TΔS

What does a negative ΔG indicate?

Exergonic and Spontaneous.

What does a positive ΔG indicate?

Endergonic and Non-Spontaneous.

What is ATP coupling?

Using the energy released by an exergonic reaction, such as ATP hydrolysis, to drive an endergonic reaction.

Why is ATP described as an energy currency?

ATP can be hydrolyzed to release usable free energy that drives cellular processes.

What bond is commonly described as a high-energy bond in ATP?

The phosphoanhydride bonds between ATP’s phosphate groups.

What happens when ATP is hydrolyzed?

ATP + H₂O → ADP + Pi, releasing free energy.

What is oxidative phosphorylation?

ATP production driven by the electron transport chain and proton gradient across the inner mitochondrial membrane.

Where is the mitochondrial ETC located?

Inner mitochondrial membrane.

What is the ultimate electron acceptor in the ETC?

Oxygen

What is oxygen reduced to at the end of the ETC?

Water (H₂O)

What are the major electron carriers that donate electrons to the ETC?

NADH and FADH₂

Which ETC complexes pump protons across the inner mitochondrial membrane?

Complexes I, III and IV.

Which ETC complex receives electrons from NADH?

Complex I

Which ETC complex receives electrons from FADH₂?

Complex II

Why does FADH₂ produce less ATP than NADH?

FADH₂ enters through Complex II, bypassing Complex I, so fewer protons are pumped.

What is Coenzyme Q (CoQ)?

A mobile electron carrier that transfers electrons from Complexes I and II to Complex III.

What is cytochrome c?

A mobile electron carrier that transfers electrons from Complex III to Complex IV.

What creates the proton gradient used for ATP synthesis?

Proton pumping by Complexes I, III and IV

What is chemiosmosis?

The movement of H⁺ down its electrochemical gradient through ATP synthase, driving ATP production.

What does ATP synthase do?

It uses the energy of the H⁺ gradient to convert ADP + Pi into ATP.

What is the approximate ATP yield from one NADH and one FADH₂?

NADH = 2.5 ATP; FADH₂ = 1.5 ATP.

Complete RACCOU with the target of each inhibitor.

R — Rotenone → Complex I
A — Antimycin A → Complex III
C — Cyanide → Complex IV
C — CO → Complex IV
O — Oligomycin → ATP synthase
U — Uncoupling → dissipates H⁺ gradient

How does oligomycin affect oxidative phosphorylation?

It inhibits ATP synthase, preventing H⁺ from flowing through the enzyme and thereby inhibiting ATP synthesis.

What is an uncoupler?

An uncoupler dissipates the proton gradient across the inner mitochondrial membrane

what happens to ATP production when oxidative phosphorylation is uncoupled?

Electron transport can continue, but ATP synthesis decreases, with energy released largely as heat.

Which ETC inhibitor is remembered by the first letter of RACCOU, and what does it inhibit?

R — Rotenone: inhibits Complex I.