Glycolysis and Fermentation

What are oxidation-reduction reactions in cells?

They transfer electrons; oxidation = loss of electrons, reduction = gain of electrons — key in energy release.

What is the role of electron carriers in metabolism?

NAD⁺ and FAD carry electrons from catabolic reactions to the electron transport chain.

What is the role of ATP in cells?

ATP stores and transfers energy for cellular work — like a rechargeable battery.

What is glycolysis

A 10-step pathway that breaks glucose (6C) into 2 pyruvate (3C) molecules, makes 2 ATP (net) and 2 NADH.

Difference between aerobic respiration and fermentation?

• Aerobic: Uses oxygen, produces ~30–32 ATP

• Fermentation: No oxygen, regenerates NAD⁺, makes only 2 ATP

How does pyruvate oxidation link glycolysis and the citric acid cycle?

Pyruvate → Acetyl-CoA + CO₂ + NADH in the mitochondrial matrix (eukaryotes).

What happens in the citric acid cycle?

Acetyl-CoA (2C) combines with oxaloacetate (4C) → citrate (6C) → releases 2 CO₂, makes 3 NADH, 1 FADH₂, 1 ATP (or GTP) per cycle.

Where does the citric acid cycle occur?

In the mitochondrial matrix (eukaryotes) or cytoplasm (prokaryotes).

What is the flow of carbon and electrons in the citric acid cycle?

Carbon enters as acetyl (2C), exits as 2 CO₂; electrons are transferred to NADH/FADH₂.

What is the electron transport chain (ETC)?

A series of membrane proteins in the inner mitochondrial membrane that pass electrons and pump protons.

How does the proton gradient drive ATP synthesis?

Protons flow back into the matrix through ATP synthase, spinning it to make ATP — this is chemiosmosis.

How many ATP are made in aerobic respiration?

About 30–32 ATP per glucose:

• Glycolysis: 2 ATP

• Citric Acid Cycle: 2 ATP

• ETC & Chemiosmosis: ~26–28 ATP