Unit 6 Cellular Respiration and Fermentation

Anaerobic respiration vs. aerobic respiration

Anaerobic respiration occurs without oxygen; aerobic respiration requires oxygen.

What is ATP?

ATP (adenosine triphosphate) is the energy molecule or "currency" used by cells to do work.

Equation for aerobic respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ~36 ATP + heat.

Which molecules are oxidized in cellular respiration?

Glucose (C₆H₁₂O₆) is oxidized.

Which molecules are reduced in cellular respiration?

Oxygen (O₂) is reduced.

Where does cellular respiration occur?

Glycolysis in cytoplasm; pyruvate oxidation, Krebs cycle, and electron transport chain in mitochondria.

Three major stages of cellular respiration

1. Glycolysis

What happens at each stage of cellular respiration?

Glycolysis breaks glucose into pyruvate, producing ATP and NADH. Krebs cycle processes Acetyl-CoA, generating NADH, FADH₂, ATP, and CO₂. ETC uses electrons from NADH and FADH₂ to produce a proton gradient that drives ATP synthesis.

Which step produces the most ATP?

Electron Transport Chain produces the most ATP (~32 ATP).

What is an electron carrier molecule? Which ones are used?

Molecules that carry electrons during reactions; NAD⁺/NADH and FAD/FADH₂ are used in cellular respiration.

How does the electron transport chain produce energy?

Electrons move through ETC complexes, pumping H⁺ ions into the intermembrane space, creating a concentration gradient. H⁺ ions flow back through ATP synthase, generating ATP by chemiosmosis.

Main advantage of fermentation over aerobic respiration

Allows ATP production without oxygen.

If 8 glucose molecules enter glycolysis, net products are

16 pyruvate molecules and 16 ATP molecules.

Where is the mitochondrial matrix?

Inside the inner membrane of mitochondria.

Do plants carry out cellular respiration?

Yes, plants perform cellular respiration to generate ATP.

What happens to glucose’s carbon atoms during aerobic respiration?

They are released as CO₂.

Complete balanced equation for cellular respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ~36 ATP + heat.

What do cells use the energy in food to make?

ATP.

Which reactant is oxidized in cellular respiration?

Glucose.

Which reactant is reduced?

Oxygen.

Main phases of cellular respiration

Glycolysis, Pyruvate oxidation, Krebs cycle, Electron Transport Chain.

Location of glycolysis in eukaryotic cells

Cytoplasm.

Location of Krebs cycle

Mitochondrial matrix.

Location of electron transport chain

Inner mitochondrial membrane.

Starting molecule of glycolysis

Glucose.

Products of glycolysis

2 pyruvate, 2 ATP (net), 2 NADH.

Net ATP produced during glycolysis

2 ATP.

Conversion before Krebs cycle

Pyruvate converted to Acetyl-CoA.

Outputs of one Krebs cycle turn

3 NADH, 1 FADH₂, 1 ATP, 2 CO₂.

Number of Krebs cycle turns per glucose

2 turns.

Net ATP produced during Krebs cycle

2 ATP.

Electron donors to ETC

NADH and FADH₂.

Final electron acceptor in ETC

Oxygen (O₂).

Byproduct formed at end of ETC

Water (H₂O).

Define chemiosmosis

Movement of H⁺ ions down their concentration gradient through ATP synthase to produce ATP.

ATP produced by ETC per glucose

Approximately 32 ATP.

When does anaerobic respiration/fermentation occur?

When oxygen is absent or scarce.

Phase common to aerobic and anaerobic respiration

Glycolysis.

End products of lactic acid fermentation

Lactic acid and 2 ATP.

End products of alcoholic fermentation

Ethanol, CO₂, and 2 ATP.

ATP produced during fermentation

2 ATP per glucose.

Why is fermentation necessary after glycolysis?

To regenerate NAD⁺ for glycolysis to continue in absence of oxygen.

NADH/FADH₂ and ATP yield from pyruvate oxidation

2 NADH, 0 ATP per glucose.

NADH/FADH₂ and ATP yield from Krebs cycle

6 NADH, 2 FADH₂, 2 ATP per glucose.

Total ATP yield per glucose from cellular respiration

About 36 ATP.

Function and location of mitochondrial cristae

Inner membrane folds increasing surface area for ETC and ATP production.

Intermembrane space in mitochondria

Space between inner and outer membranes where H⁺ ions accumulate.

Effect of ETC poison on ATP production

ATP synthesis stops or decreases significantly.

Why plants carry out photosynthesis and respiration

Photosynthesis produces glucose and oxygen; respiration breaks down glucose to produce ATP.

How lipids and proteins can generate ATP

They are broken down into molecules that enter glycolysis or Krebs cycle.

Cellular respiration definition

Breakdown of glucose in the presence of oxygen to produce CO₂, water, and ATP.