Chapter 9: Cellular Respiration & Fermentation

Glycolysis

The anaerobic breakdown of glucose into pyruvate, producing ATP and NADH.

Cellular respiration

A metabolic process that extracts energy from organic molecules using oxygen.

Fermentation

A metabolic process that allows ATP production without oxygen by regenerating NAD+.

Aerobic

A process that requires oxygen.

Anaerobic

A process that occurs without oxygen.

Redox reaction

A chemical reaction involving the transfer of electrons.

Oxidation

The loss of electrons from a molecule.

Reduction

The gain of electrons by a molecule.

Oxidizing agent

A molecule that accepts electrons.

Reducing agent

A molecule that donates electrons.

ATP (Adenosine Triphosphate)

The primary energy carrier in cells.

ADP (Adenosine Diphosphate)

A lower-energy molecule that can be converted into ATP.

NAD+ (Nicotinamide Adenine Dinucleotide)

An electron carrier that is reduced to NADH during glycolysis and the Krebs cycle.

NADH

The reduced form of NAD+, carrying electrons to the electron transport chain.

FADH2

1. A molecule that stores energy for the electron transport chain.

Mitochondria

The organelle where cellular respiration occurs.

Cytoplasm

The location of glycolysis in the cell.

Aerobic respiration

Respiration using oxygen as the final electron acceptor

Anaerobic respiration

Respiration using molecules other than oxygen as electron acceptors.

Krebs Cycle (Citric Acid Cycle or TCA Cycle)

A cycle that oxidizes acetyl-CoA to produce NADH, FADH2, ATP, and CO2.

Substrate-level phosphorylation

ATP production through enzyme-mediated transfer of a phosphate group

Oxidative phosphorylation

ATP synthesis powered by redox reactions in the electron transport chain.

Electron Transport Chain (ETC)

A series of proteins that transfer electrons, creating a proton gradient for ATP synthesis.

Chemiosmosis

The process by which ATP is produced using a proton gradient.

Cytochromes

Proteins in the ETC that transfer electrons.

Ubiquinone (Q)

A lipid-soluble electron carrier in the ETC.

ATP synthase

An enzyme that synthesizes ATP using a proton gradient.

Gluconeogenesis

The process of forming glucose from non-carbohydrate sources.

UCP1 (Uncoupling Protein 1)

A protein that dissipates the proton gradient to generate heat instead of ATP.

Superoxide

1. A reactive oxygen species formed during cellular respiration.

Hydroxyl radicals

Highly reactive oxygen species that can damage biomolecules.

Concepts

Principles that govern metabolic pathways

Energy flow, enzyme regulation, and feedback mechanisms.

Cellular respiration equation

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP.

ΔG from glucose combustion

Cellular respiration is exergonic, releasing free energy.

Energy harvesting from glucose

Breakdown into ATP, NADH, and FADH2.

Why redox reactions release energy

Electrons move to more

Why redox reactions release energy

Electrons move to more electronegative acceptors, releasing energy.

Energy pathway locations

Glycolysis in cytoplasm, Krebs cycle and ETC in mitochondria.

Aerobic respiration vs. fermentation

Oxygen use and ATP yield differences

Catabolic and anabolic interconversions

How molecules are broken down or synthesized.

How cells regulate catabolic vs. anabolic pathways

Feedback inhibition and enzyme regulation.

Significance of UCP1 in mitochondria

Heat generation instead of ATP production.

Negative vs. positive feedback in metabolism

Regulation mechanisms for metabolic pathways.

Main control points in respiration

Phosphofructokinase, isocitrate dehydrogenase, and acetyl-CoA regulation

Glycolysis

ATP used and produced

2 ATP used, 4 ATP produced (net 2 ATP).

NADH produced

2 NADH.

Pyruvate produced

2 pyruvate molecules.

Steps 6 and 7 details

Enzymes, substrates, and products involved.

Substrate-level or oxidative phosphorylation?

Glycolysis uses substrate-level phosphorylation.

CO2 and FADH2 production?

No CO2 or FADH2 produced in glycolysis

Pyruvate Oxidation:

Acetyl-CoA, CO2, and NADH production

1. 2 acetyl-CoA, 2 CO2, 2 NADH per glucose.

ATP production?

No ATP is directly produced in pyruvate oxidation.

Function of pyruvate dehydrogenase

Converts pyruvate into acetyl-CoA.

Citric Acid Cycle (Krebs Cycle):

CO2, ATP (GTP), NADH, and FADH2 production

4 CO2, 2 ATP (GTP), 6 NADH, 2 FADH2 per glucose.

Steps 1 and 8 details

Key enzymes and substrates.

ATP production mechanism

Substrate-level phosphorylation.

Oxidative Phosphorylation:

Two stages

Electron transport chain and chemiosmosis.

ATP yield from oxidative phosphorylation

~28-34 ATP per glucose.

Why so many steps?

Controlled energy release and efficient ATP production.

Electron carriers and their functions

NADH, FADH2, cytochromes, ubiquinone.

Concentration gradient formation

Proton pumping into the intermembrane space.

ATP synthase function and structure

Uses proton flow to synthesize ATP.

ATP synthase as an ATPase?

Yes, it can also hydrolyze ATP when needed.

Why ATP synthesis is favored

Proton gradient and chemiosmosis drive ATP formation.

Experiment demonstrating chemiosmosis

Showed proton gradients power ATP synthesis.

NAD+ regeneration in oxidative phosphorylation

Through electron donation to the ETC.

Superoxide and hydroxyl radical formation

By-products of oxidative phosphorylation.

Health effects of reactive oxygen species

DNA, protein, and membrane damage.

How the body removes radicals

1. Antioxidants like Vitamin E and enzymes.

1. antioxidant like Vitamin E and enzymes.

2. n antioxidant - True.

1. True.

Fermentation

Lactic acid fermentation organisms

Muscle cells, some bacteria.

Pyruvate oxidation or reduction

Pyruvate is reduced.

NADH oxidation or reduction?

1. NADH is oxidized.

Lactic acid molecules per glucose

2 lactic acid molecules.

NAD+ regeneration mechanism

Reduction of pyruvate.

Alcohol fermentation organisms

Yeast, some bacteria.

Products of alcohol fermentation

Ethanol and CO2

Number of CO2 and ethanol molecules produced

2 CO2, 2 ethanol per glucose.

Acetaldehyde oxidation or reduction?

Acetaldehyde is reduced.

NAD+ regeneration in alcohol fermentation

Acetaldehyde reduction.