C 1.2 cell respiration

What is the main purpose of cell respiration?

To make ATP for energy storage and transfer.

What is the structure of ATP?

Ribose + adenine + three phosphate groups.

Why is ATP useful?

Soluble, stable at neutral pH, transfers energy between cell processes.

What life processes require ATP?

Macromolecule synthesis, active transport, movement.

What are the waste products of aerobic respiration?

CO₂ and water.

What are the waste products of anaerobic respiration?

CO₂ + lactate (animals) or ethanol (yeast).

ATP yield: aerobic vs anaerobic?

Aerobic: 30+ ATP/glucose; anaerobic: 2 ATP/glucose.

Where does aerobic respiration occur?

Cytoplasm + mitochondria.

Where does anaerobic respiration occur?

Cytoplasm only.

What are the steps to anaerobic respiration

Anaerobic occurs in the cytoplasm and without the presence of oxygen. It is also less efficient in producing ATP

In animals and humans lactate acid fermentation occurs where pyruvate (3c) is converted into lactate (3c). NADH is oxidized to NAD+ and the regeneration of NADH allows glycolysis to make 2 ATP molecules

In yeast alcoholic fermentation occurs where pyruvate (3c) is converted to ethanol (2c). NADH is oxidized to NAD+ , and pyruvate is going to undergo decarboxylation where it loses carbon in the form of CO2.

What does NAD do?

Carries electrons and hydrogen between respiration reactions.

What is oxidation?

Loss of electrons.

What is reduction?

Gain of electrons

Explain the steps of glycolysis.

Glucose is phosphorylated → split into two 3‑carbon molecules → oxidized → forms 2 pyruvate, 2 reduced NAD, net 2 ATP. ( you explain more in details )

Where does glycolysis occur?

cytoplasm

What does glycolysis require?

Glucose, ATP, ADP, and enzymes

What is the end product of glycolysis?

Pyruvate.

What happens to pyruvate in anaerobic respiration (animals)?

Converted to lactate to regenerate NAD.

What happens to pyruvate in yeast anaerobic respiration?

Converted to ethanol + CO₂.

Why is anaerobic respiration important?

Restores NAD so glycolysis can continue making ATP.

Explain the steps of the link reaction.

Pyruvate enters mitochondria → decarboxylated (CO₂ removed) → oxidized → combines with coenzyme A → forms acetyl‑CoA. ( you explain in more detail)

Where does the link reaction occur?

Mitochondrial matrix

Explain the steps of the Krebs cycle.

Acetyl‑CoA enters cycle → combines with citrate → carbon removed as CO₂ → NADH and FADH₂ generated → ATP produced → coenzyme A regenerated. ( you explain in more detail)

What are the outputs per cycle?

3 NADH, 1 ATP, 2 CO₂, 1 FADH₂.

Where does the Krebs cycle occur?

Mitochondrial matrix.

Explain the steps of the electron transport chain.

The electron transport chain happens in the inner mitochondrial membrane

NADH undergoes oxidation by transferring protons out of the matrix of the mitochondria into the intermembrane space

The electrons pass through an electron transport chain.

FADH2 brings electrons into the chain at a later stage powering the transfer of electrons into the intermembrane space creating a high concentration gradient of protons.

Oxygen as the final electron acceptor combines with two protons to make H2O (water)

Through the process of Chemiosmosis protons go through the atp synthase down their concentration gradient and their energy is used to phosphorylate ADP to ATP

Where does the ETC occur?

Inner mitochondrial membrane (cristae).

What final molecule accepts electrons?

oxygen

What drives ATP synthase?

Proton gradient (high → low concentration flow).

Why do lipids produce more energy than carbohydrates?

Lipids yield ~37 kJ/g vs 17 kJ/g; more hydrogen for oxidation.

Why can lipids not undergo anaerobic respiration?

They must first be oxidized to acetyl groups that enter the Krebs cycle.