3/4- link reaction, Kreb's cycle and oxidative phosphorylation

What is the difference between the link reaction, Kreb's cycle and oxidative phosphorylation?

The link reaction converts pyruvate into acetyl-CoA, the Krebs cycle oxidises acetyl-CoA to produce reduced coenzymes, and oxidative phosphorylation uses those coenzymes and oxygen to synthesise large amounts of ATP.

Where does the electron transport chain take place?

The inner mitochondrial membrane, using integral membrane proteins.

What is the electron transport chain (ETC)?

A series of membrane-bound proteins that transfer electrons and use their energy to make ATP.

Name the main protein complexes involved in the ETC.

Complex I, Complex II, Complex III, Complex IV, and ATP synthase.

What happens when NADH enters the electron transport chain?

NADH binds to Complex I and is oxidised to NAD+, releasing protons (H+) and electrons (e−).

Where does FADH2 enter the electron transport chain?

At Complex II, not Complex I.

What happens to NAD and FAD after they release hydrogen?

They return to the Krebs cycle to collect more hydrogen.

What happens to electrons as they pass along the electron transport chain?

They lose energy, which is used to pump protons across the inner mitochondrial membrane.

How is the proton gradient formed in the ETC?

Protons are actively transported from the mitochondrial matrix to the intermembrane space.

What type of transport moves protons across the inner mitochondrial membrane?

Active transport using energy from electrons.

Why is the proton gradient important?

It stores potential energy that is used to synthesise ATP.

What is chemiosmosis?

The movement of protons down their concentration gradient through ATP synthase to produce ATP.

Who discovered chemiosmosis?

Peter Mitchell in the 1960s.

What is the role of ATP synthase?

It allows protons to flow back into the matrix and uses their energy to synthesise ATP.

How many protons are needed to synthesise one ATP molecule?

Four protons.

What happens to electrons at the end of the electron transport chain?

They combine with protons and oxygen to form water.

What is the role of oxygen in respiration?

It acts as the final electron acceptor in the electron transport chain.

Why does the ETC stop without oxygen?

Electrons cannot be removed from the chain, so proton pumping and ATP synthesis stop.

How does oxygen enter the mitochondria?

By lipid diffusion across cell and mitochondrial membranes.

What is oxidative phosphorylation?

The synthesis of ATP using energy from electrons in the presence of oxygen.

Why is ATP synthesis called oxidative phosphorylation?

Because oxygen is used and ADP is phosphorylated to form ATP.

Write the equation showing oxidation of NADH.

NADH → NAD⁺ + H⁺ + e⁻

Write the equation for water formation in respiration.

O₂ + H⁺ + e⁻ → H₂O

Write the equation for ATP synthesis.

ADP + Pi → ATP

What happens if proton channels form in the inner mitochondrial membrane?

Protons bypass ATP synthase, reducing ATP production.

How do some poisons affect oxidative phosphorylation?

They create proton channels that stop ATP synthesis.

What happens in brown fat tissue of newborn babies?

Respiration occurs but no ATP is made; energy is released as heat.

Why is heat produced instead of ATP in brown fat tissue?

Protons bypass ATP synthase so the proton gradient energy is released as heat.