Cellular Respiration Booster Notes

50 vocabulary flashcards covering essential terms and definitions from the Cellular Respiration lecture notes.

Cellular Respiration

Exergonic pathway that oxidizes glucose and channels released electrons through the ETC to make ATP.

Glycolysis

Cytosolic breakdown of glucose to 2 pyruvate, yielding a net 2 ATP and 2 NADH.

Substrate-Level Phosphorylation

Direct ATP formation by transferring a phosphate group from a high-energy intermediate to ADP.

Hexokinase

Irreversibly phosphorylates glucose to glucose-6-phosphate, consuming 1 ATP; first committed step of glycolysis.

Phosphofructokinase (PFK)

Regulatory enzyme that adds a second phosphate to fructose-6-phosphate, fully committing it to glycolysis.

Aerobic Respiration

Form of respiration that uses O2 as the terminal electron acceptor in the ETC.

Anaerobic Respiration

ATP production without oxygen, relying on glycolysis plus fermentation to regenerate NAD+.

Overall Aerobic Reaction

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP.

NAD+

Oxidized electron carrier that accepts electrons during glycolysis and the CAC.

NADH

Reduced form of NAD+ that donates high-energy electrons to the ETC.

Pyruvate Decarboxylation

Conversion of pyruvate to acetyl-CoA, CO2, and NADH in the mitochondrial matrix.

Pyruvate Dehydrogenase Complex (PDC)

Multi-enzyme complex that catalyzes pyruvate decarboxylation to acetyl-CoA.

Acetyl-CoA

Two-carbon molecule that condenses with oxaloacetate to enter the citric acid cycle.

Citric Acid Cycle (CAC) / Krebs Cycle

Matrix reactions that oxidize acetyl-CoA, producing CO2, ATP, NADH, and FADH2.

Oxaloacetate

Four-carbon molecule regenerated each CAC turn to bind incoming acetyl-CoA.

FADH2

Reduced flavin carrier generated in the CAC; feeds electrons to the ETC at complex II.

Electron Transport Chain (ETC)

Series of inner-membrane proteins that pass electrons and pump protons to build a gradient.

Oxidative Phosphorylation

ATP synthesis driven by oxidation of NADH/FADH2 and the resulting proton gradient.

Chemiosmosis

Flow of protons down their electrochemical gradient through ATP synthase to make ATP.

Proton Motive Force

Stored energy in the H+ gradient across the inner mitochondrial membrane.

ATP Synthase

Membrane enzyme that couples proton flow to phosphorylation of ADP, forming ATP.

Oxygen (Final Electron Acceptor)

Accepts electrons and protons at the end of the ETC to form H2O.

Alcohol Fermentation

Yeast/plants pathway converting pyruvate to ethanol and CO2 while regenerating NAD+.

Acetaldehyde

Intermediate in alcohol fermentation that accepts electrons from NADH to become ethanol.

Lactic Acid Fermentation

Muscle/microbe pathway reducing pyruvate to lactate, oxidizing NADH to NAD+.

Lactate

Product of lactic fermentation that can be transported to the liver for glucose synthesis.

Gluconeogenesis

Liver process that makes glucose from non-carbohydrate precursors when glucose is scarce.

Glycogen

Branched glucose polymer stored in liver and skeletal muscle as energy reserve.

Alternative Energy Sources

Carbohydrates, fats, then proteins catabolized for ATP when glucose levels are low.

Glucose

Six-carbon sugar serving as the primary fuel for cellular respiration.

ATP

Cell’s main energy currency produced by substrate-level and oxidative phosphorylation.

Carbon Dioxide (CO2)

Gas released during the CAC and pyruvate decarboxylation.

Water (H2O)

Product formed when oxygen accepts electrons and protons at the end of the ETC.

H+ Gradient

Difference in proton concentration across the inner membrane created by ETC pumping.

Inner Mitochondrial Membrane

Location of the ETC and ATP synthase machinery.

Mitochondrial Matrix

Internal compartment housing the CAC and PDC.

Exergonic Reaction

Reaction that releases free energy; cellular respiration overall is exergonic.

Glucose-6-Phosphate

Phosphorylated glucose trapped inside the cell following the hexokinase reaction.

Substrate-Level vs. Oxidative Phosphorylation

Direct phosphate transfer in cytosol vs. ATP made via ETC-driven proton gradient.

Regeneration of NAD+

Reoxidation of NADH in ETC or fermentation to keep glycolysis/CAC running.

Final Electron Acceptor

Molecule that receives electrons at the end of respiration—O2 in aerobic, acetaldehyde or pyruvate in fermentation.

ATP Yield of Glycolysis

Net gain of 2 ATP per glucose through substrate-level phosphorylation.

ATP Yield of Citric Acid Cycle

One ATP (or GTP) per turn, giving 2 ATP per glucose molecule.

NADH Oxidation

Process where NADH donates electrons to the ETC, driving proton pumping.

FADH2 Oxidation

Electron donation from FADH2 to ETC complex II, generating fewer protons than NADH.

Cori Cycle

Pathway that converts muscle lactate back to glucose in the liver.

Beta-Oxidation

Catabolic breakdown of fatty acids into acetyl-CoA for the CAC.

Deamination

Removal of amino groups from proteins so carbon skeletons can enter energy pathways.

Committed Step

Enzymatic reaction after which a substrate is destined for a specific pathway, e.g., PFK in glycolysis.

Chemiosmotic Theory

Peter Mitchell’s concept that a proton gradient across a membrane drives ATP synthesis.