Energy-Generating Pathways & Fermentation

Vocabulary flashcards covering key terms related to cellular respiration, fermentation pathways, microbial products, and ATP yield differences.

ATP (Adenosine Triphosphate)

Universal energy currency of the cell produced during respiration and fermentation.

Cellular Respiration

Metabolic process in which electrons from NADH/FADH₂ pass through an ETC to a final electron acceptor, generating large amounts of ATP.

Aerobic Respiration

Type of cellular respiration that uses oxygen (O₂) as the final electron acceptor, yielding the most ATP.

Anaerobic Respiration

Respiration using an inorganic molecule other than oxygen (e.g., nitrate, sulfate) as the final electron acceptor; produces moderate ATP.

Fermentation

Energy-producing pathway that uses an organic molecule (acid or alcohol) as the final electron acceptor; functions with or without O₂ and produces little ATP.

Glycolysis

First step of all energy pathways; splits glucose into pyruvate in the cytoplasm, generating small amounts of ATP and NADH.

Krebs Cycle (Citric Acid Cycle)

Series of reactions oxidizing acetyl-CoA to CO₂ while producing NADH, FADH₂ and ATP/GTP; occurs in cytoplasm of prokaryotes and mitochondria of eukaryotes.

Electron Transport Chain (ETC)

Membrane-bound series of redox carriers that pass electrons to the final acceptor and pump protons to drive ATP synthesis.

Final Electron Acceptor

Substance that receives electrons at the end of the ETC or during fermentation, determining whether the process is aerobic, anaerobic, or fermentative.

NADH

Reduced electron carrier formed in glycolysis and the Krebs cycle; donates electrons to the ETC.

FADH₂

Reduced electron carrier produced in the Krebs cycle; donates electrons to the ETC.

Prokaryotic Respiration Location

Glycolysis & Krebs cycle occur in cytoplasm; ETC is embedded in the plasma membrane.

Eukaryotic Respiration Location

Glycolysis occurs in cytoplasm; Krebs cycle in mitochondrial matrix; ETC on inner mitochondrial membrane.

Lactic Acid Fermentation

Conversion of pyruvate to lactic acid; used by muscle cells and bacteria such as Streptococcus and Lactobacillus for yogurt and sauerkraut.

Alcohol Fermentation

Yeast-driven process converting pyruvate to ethanol and CO₂; basis for beer, wine, and bread rising.

Acetone-Butanol-Ethanol (ABE) Fermentation

Clostridium acetobutylicum pathway producing acetone, butanol, and ethanol—important industrial solvents and potential biofuels.

Butanediol Fermentation

Pathway in Enterobacter and Klebsiella that yields 2,3-butanediol, acetoin, CO₂, and H₂.

Butyric Acid Fermentation

Clostridium butyricum pathway producing butyric acid, CO₂, and H₂; contributes to butter flavor and rancidity.

Gas Gangrene

Tissue-destroying condition often caused by fermentative Clostridium species that produce gas and toxins in anaerobic wounds.

ATP Yield Comparison

Aerobic respiration = lots of ATP; anaerobic respiration = some ATP; fermentation = small amounts of ATP.