Biology – Cellular Respiration and Fermentation (Chapter 7)

Vocabulary flashcards covering key terms and definitions from Chapter 7: Cellular Respiration and Fermentation.

Cellular respiration

Process by which living cells extract energy from organic molecules, primarily to make ATP.

Aerobic respiration

Form of cellular respiration that consumes O₂ and releases CO₂.

Anaerobic respiration

Respiratory process that uses a molecule other than O₂ as the final electron acceptor in the electron transport chain.

Fermentation

ATP production exclusively by substrate-level phosphorylation with no net oxidation of organic molecules; regenerates NAD⁺ from NADH.

Glycolysis

Ten-step pathway in the cytosol that splits glucose into two pyruvate, producing 2 ATP and 2 NADH.

Energy investment phase

First phase of glycolysis in which 2 ATP are hydrolyzed to phosphorylate glucose, forming fructose-1,6-bisphosphate.

Cleavage phase (glycolysis)

Middle phase of glycolysis where fructose-1,6-bisphosphate is split into two glyceraldehyde-3-phosphate molecules.

Energy liberation phase

Final phase of glycolysis that converts glyceraldehyde-3-phosphate to pyruvate, yielding 2 NADH and 4 ATP.

Phosphofructokinase

Rate-limiting glycolytic enzyme; inhibited allosterically by high ATP levels.

Substrate-level phosphorylation

Direct synthesis of ATP by transferring a phosphate group from a high-energy substrate to ADP.

Pyruvate dehydrogenase

Large enzyme complex in the mitochondrial matrix that converts pyruvate into acetyl-CoA, CO₂, and NADH.

Acetyl-CoA

Two-carbon acetyl group bound to coenzyme A; enters the citric acid cycle.

Citric acid cycle (Krebs cycle)

Eight-step metabolic cycle in the mitochondrial matrix that produces 2 CO₂, 3 NADH, 1 FADH₂, and 1 ATP per acetyl-CoA.

Oxaloacetate

Four-carbon molecule that combines with acetyl-CoA to form citrate and is regenerated each turn of the citric acid cycle.

NADH

High-energy electron carrier that donates electrons to Complex I of the electron transport chain.

FADH₂

Electron carrier formed in the citric acid cycle; donates electrons to Complex II (succinate reductase).

Oxidative phosphorylation

ATP production powered by the oxidation of NADH/FADH₂ via the electron transport chain and chemiosmosis.

Electron transport chain (ETC)

Series of protein complexes and small molecules in the inner mitochondrial membrane that transfer electrons and pump H⁺.

Chemiosmosis

Use of an H⁺ electrochemical gradient to drive ATP synthesis through ATP synthase.

ATP synthase

Rotary enzyme that synthesizes ATP from ADP and Pi as H⁺ flows through it down its gradient.

H⁺ electrochemical gradient

Proton motive force across the inner mitochondrial membrane generated by ETC-driven H⁺ pumping.

Cytochrome oxidase (Complex IV)

Final ETC complex that transfers electrons to O₂, producing H₂O; inhibited by cyanide and CO.

NADH dehydrogenase (Complex I)

First ETC complex that accepts electrons from NADH and pumps H⁺ into the intermembrane space.

Succinate reductase (Complex II)

ETC complex that accepts electrons from FADH₂ but does not pump protons.

Ubiquinone (CoQ)

Mobile lipid-soluble electron carrier that transfers electrons from Complex I or II to Complex III.

Feedback inhibition

Regulatory mechanism wherein a high concentration of an end product (e.g., ATP) inhibits an earlier enzyme.

Racker & Stoeckenius experiment

Inserted ATP synthase and bacteriorhodopsin into vesicles; light-driven H⁺ pumping confirmed that ATP synthase uses an H⁺ gradient.

Yoshida & Kinosita experiment

Directly visualized rotation of the γ subunit of ATP synthase using a fluorescent actin filament.

Lactic acid fermentation

Anaerobic pathway in muscle cells where pyruvate is reduced to lactate, regenerating NAD⁺.

Alcohol fermentation

Anaerobic process in yeast where pyruvate is converted to CO₂ and ethanol, regenerating NAD⁺.

Nitrate reductase

Enzyme used by anaerobic bacteria (e.g., E. coli) to reduce NO₃⁻ to NO₂⁻ at the end of their ETC.

Pyruvate/H⁺ symporter

Transport protein in the inner mitochondrial membrane that co-imports pyruvate with a proton.

Respiratory chain

Alternative name for the electron transport chain in aerobic organisms.

Maximum ATP yield per glucose

Approximately 30–34 ATP, combining substrate-level phosphorylation and oxidative phosphorylation.