Cellular Respiration & Fermentation – Chapter 9 (Part 1)

Vocabulary flashcards covering key terms and definitions from Chapter 9 Part 1 on cellular respiration, fermentation, and related metabolic concepts.

ATP (Adenosine Triphosphate)

Primary energy currency of the cell whose hydrolysis drives cellular work; produced continually because it is unstable and short-lived.

Cellular Respiration

Set of catabolic reactions that oxidize high-energy molecules (usually glucose) and use released electrons to generate ATP.

Fermentation

Anaerobic pathway that partially oxidizes glucose, producing ATP and small, reduced organic waste products; yields less energy than cellular respiration.

Redox Reaction

Chemical reaction involving electron transfer; oxidation loses electrons, reduction gains them—core of energy harvest in respiration.

Glycolysis

Ten-step pathway in the cytosol that breaks one glucose (6 C) into two pyruvate (3 C), yielding net 2 ATP and 2 NADH.

Energy-Investment Phase (Glycolysis)

First five glycolytic reactions in which 2 ATP are consumed to phosphorylate intermediates and raise their potential energy.

Energy-Payoff Phase (Glycolysis)

Last five glycolytic reactions that generate 4 ATP (net 2), 2 NADH, and 2 pyruvate via substrate-level phosphorylation.

Substrate-Level Phosphorylation

Direct enzymatic transfer of a phosphate group from a phosphorylated substrate to ADP, forming ATP (occurs in glycolysis and citric acid cycle).

Pyruvate Processing

Conversion of pyruvate to acetyl CoA by the multi-enzyme complex pyruvate dehydrogenase; produces CO₂ and NADH.

Pyruvate Dehydrogenase

Large enzyme complex in mitochondrial matrix (eukaryotes) or cytosol (prokaryotes) that oxidizes pyruvate to acetyl CoA.

Acetyl CoA

Two-carbon acetyl group attached to coenzyme A; entry molecule for the citric acid cycle.

Citric Acid Cycle (Krebs Cycle)

Eight-enzyme cyclic pathway in the mitochondrial matrix (or prokaryotic cytosol) that fully oxidizes acetyl CoA to CO₂ and captures energy in NADH, FADH₂, and ATP/GTP.

Oxaloacetate

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

NADH

Reduced form of the coenzyme NAD⁺ that carries high-energy electrons to the electron transport chain.

FADH₂

Reduced form of the coenzyme FAD produced in the citric acid cycle; donates electrons to the electron transport chain.

Electron Transport Chain (ETC)

Series of membrane-bound protein complexes that transfer electrons from NADH/FADH₂ to O₂, pumping protons to create an electrochemical gradient.

Oxidative Phosphorylation

ATP synthesis powered by the proton gradient established by the ETC; catalyzed by ATP synthase.

Cristae

Folded inner-membrane structures of mitochondria that increase surface area for the ETC and ATP synthase.

Mitochondrial Matrix

Innermost compartment of mitochondria where pyruvate processing and the citric acid cycle occur.

Catabolic Pathway

Metabolic series that breaks down molecules, releasing energy often captured in ATP (e.g., cellular respiration).

Anabolic Pathway

Metabolic series that builds larger molecules from smaller ones, consuming energy (usually ATP).

Homeostasis (Metabolic)

Regulation of interconnected metabolic pathways to maintain stable internal conditions despite environmental changes.

Glycogen

Branched polymer of glucose that animals store as a carbohydrate energy reserve, later supplying substrates for ATP production.

Substrate Versatility

Feature of cellular respiration whereby carbohydrates, fats, and proteins can all be converted into pathway intermediates for ATP generation.

Energy Yield of Glucose Oxidation

Complete oxidation of one glucose produces 6 CO₂, ~4 ATP (substrate-level), 10 NADH, and 2 FADH₂ whose electrons drive further ATP synthesis via oxidative phosphorylation.