Cellular Respiration 2

Three stages of cellular respiration

1) Glycolysis, 2) Citric Acid Cycle (TCA), 3) Oxidative Phosphorylation.

Where glycolysis occurs

In the cytoplasm; breaks down glucose into 2 pyruvate molecules.

Two phases of glycolysis

Energy investment phase and energy payoff phase.

Net ATP gain from glycolysis

2 ATP per molecule of glucose.

Enzyme that starts glycolysis

Hexokinase; requires Mg²⁺.

Enzyme that regulates glycolysis

Phosphofructokinase.

Molecules produced during glycolysis payoff phase

ATP and NADH.

What happens to pyruvate before entering TCA cycle

It is converted to acetyl-CoA.

What one turn of TCA cycle produces

1 GTP, 3 NADH, 1 FADH₂ per acetyl-CoA.

Total yield from two turns of TCA cycle per glucose molecule

2 ATP (or GTP), 6 NADH, 2 FADH₂.

Steps of oxidative phosphorylation

Electron transport and chemiosmosis.

Role of oxygen in oxidative phosphorylation

It is the final electron acceptor, forming water.

What happens in the electron transport chain

Electrons from NADH and FADH₂ pass through complexes to O₂, releasing energy.

What is chemiosmosis

H⁺ ions move across the mitochondrial membrane through ATP synthase, driving ATP production.

What ATP synthase does

Uses the proton gradient to synthesize ATP from ADP and inorganic phosphate.

Complexes that pump H⁺ ions into intermembrane space

Complex I and III transport 4 H⁺ each; Complex IV completes the process with O₂.

Net ATP yield after all stages of respiration

About 32 ATP per glucose molecule.

How TCA cycle is regulated

By the availability of NAD⁺ and the need for ATP.

How oxidative phosphorylation is regulated

By oxygen availability and demand for ATP.

Role of NADH and FADH₂

They carry high-energy electrons to the electron transport chain.