AP BIO RESPIRATION

What is cellular respiration?

Breaking down glucose to release energy and make ATP.

What is the overall equation for cellular respiration?

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP.

What are the four main stages of cellular respiration?

Glycolysis, pyruvate oxidation, Krebs cycle, and oxidative phosphorylation.

What is the difference between aerobic and anaerobic?

• Aerobic uses oxygen

• Anaerobic happens without oxygen.

What are NADH and FADH₂?

Electron carriers that deliver high-energy electrons to the electron transport chain.

What is glycolysis, and where does it occur?

Glucose splits into two pyruvates in the cytosol.

What are glycolysis's inputs?

1 glucose, 2 NAD⁺, and 2 ATP

What are glycolysis's outputs?

2 pyruvate, 2 NADH, and 4 ATP produced (2 ATP net).

Why is glycolysis important?

It begins glucose breakdown and can occur with or without oxygen.

What happens during pyruvate oxidation?

Each 3-carbon pyruvate loses CO₂ and becomes a 2-carbon acetyl group.

Where does pyruvate oxidation occur?

In the mitochondrial matrix.

What are the inputs and outputs of pyruvate oxidation per glucose?

Inputs: 2 pyruvate and 2 NAD⁺. Outputs: 2 acetyl-CoA, 2 CO₂, and 2 NADH.

What is acetyl-CoA?

A 2-carbon acetyl group attached to coenzyme A; it enters the Krebs cycle.

What is the Krebs cycle, and where does it occur?

A cycle that breaks down acetyl groups and releases CO₂ in the mitochondrial matrix.

What happens to carbon during the Krebs cycle?

The remaining carbons are released as CO₂.

What are the Krebs cycle's inputs per glucose?

2 acetyl groups, 6 NAD⁺, 2 FAD, and 2 ADP + 2 Pi.

What are the Krebs cycle's outputs per glucose?

4 CO₂, 6 NADH, 2 FADH₂, and 2 ATP.

Why does the Krebs cycle happen twice per glucose?

One glucose produces 2 pyruvates, which form 2 acetyl-CoA.

What is substrate-level phosphorylation?

Making ATP by directly transferring a phosphate to ADP.

What are the total products before oxidative phosphorylation?

Per glucose: 4 ATP total produced (2 net in glycolysis), 10 NADH, 2 FADH₂, and 6 CO₂.

What is oxidative phosphorylation?

The final step of cellular respiration, where the cells use oxygen to turn NADH FADH₂ into massive amounts of atp

Where does the electron transport chain (ETC) occur?

In the inner mitochondrial membrane.

What happens to NADH and FADH₂ in the ETC?

They donate electrons and become NAD⁺ and FAD again.

What happens to electrons in the ETC?

They lose energy as they pass through carriers; this energy pumps H⁺ ions.

What is a proton gradient?

A difference in H⁺ concentration across a membrane; more H⁺ builds up in the intermembrane space.

What is oxygen's role in cellular respiration?

Oxygen is the final electron acceptor; it combines with electrons and H⁺ to form water.

What is the difference between the matrix and intermembrane space?

Matrix: inside the inner membrane. Intermembrane space: between the two mitochondrial membranes.

Why does FADH₂ produce less ATP than NADH?

FADH₂ enters the ETC later, so its electrons release less usable energy for pumping H⁺.

What is fermentation, and where does it occur?

A cytosol process that regenerates NAD⁺ when oxygen is unavailable.

Why is NAD⁺ important during fermentation?

It allows glycolysis to continue; without it, glycolysis stops producing ATP.

What is alcohol fermentation?

Pyruvate becomes ethanol + CO₂, and NADH becomes NAD⁺. Yeast uses this process

What is lactic acid fermentation?

Pyruvate becomes lactic acid, and NADH becomes NAD⁺. It can occur in muscle cells when oxygen is insufficient.