Cellular Respiration Cheat Sheet

The core ideas of Cellular Respiration distilled into a single, scannable reference — perfect for review or quick lookup.

PiqCue — piqcue.com/cellular-respiration/cheatsheet

Quick Reference

Glycolysis

The first stage of cellular respiration, occurring in the cytoplasm. It splits one glucose molecule (6 carbons) into two pyruvate molecules (3 carbons each), producing a net gain of 2 ATP and 2 NADH without requiring oxygen.

Krebs Cycle (Citric Acid Cycle)

A series of chemical reactions in the mitochondrial matrix that oxidizes acetyl-CoA (derived from pyruvate) to CO2, generating NADH, FADH2, and a small amount of ATP (or GTP) per cycle turn.

Electron Transport Chain (ETC)

A series of protein complexes embedded in the inner mitochondrial membrane that transfer electrons from NADH and FADH2 to oxygen, creating a proton gradient used to drive ATP synthesis via chemiosmosis.

Aerobic vs. Anaerobic Respiration

Aerobic respiration requires oxygen as the final electron acceptor and produces 36-38 ATP per glucose. Anaerobic respiration (fermentation) occurs without oxygen, regenerating NAD+ to allow glycolysis to continue, but produces only 2 ATP per glucose.

ATP (Adenosine Triphosphate)

The primary energy currency of the cell. Energy is released when ATP is hydrolyzed to ADP and inorganic phosphate. Cellular respiration is the main process that regenerates ATP from ADP.

Key Terms at a Glance

Glycolysis:The first stage of cellular respiration, occurring in the cytoplasm, that splits glucose into two pyruvate molecules with a net yield of 2 ATP and 2 NADH.

Krebs Cycle:Also called the citric acid cycle; a series of reactions in the mitochondrial matrix that oxidizes acetyl-CoA to CO2, producing NADH, FADH2, and ATP.

Electron Transport Chain:A series of protein complexes in the inner mitochondrial membrane that transfer electrons from NADH and FADH2 to oxygen, creating a proton gradient for ATP synthesis.

Chemiosmosis:The process by which the flow of protons through ATP synthase, driven by a concentration gradient, produces ATP.

ATP Synthase:A membrane enzyme that uses the proton motive force to catalyze the synthesis of ATP from ADP and inorganic phosphate.

NAD+ / NADH:A coenzyme that acts as an electron carrier. NAD+ is the oxidized form that accepts electrons; NADH is the reduced form that donates electrons to the ETC.

FAD / FADH2:A coenzyme that acts as an electron carrier, similar to NAD+. FADH2 donates electrons to Complex II of the ETC, yielding fewer ATP than NADH.

Acetyl-CoA:A two-carbon molecule attached to coenzyme A, formed from pyruvate oxidation. It enters the Krebs cycle and is fully oxidized to CO2.

Fermentation:An anaerobic process that regenerates NAD+ from NADH, allowing glycolysis to continue. Produces ethanol (alcoholic) or lactate (lactic acid) as byproducts.

Substrate-Level Phosphorylation:The direct transfer of a phosphate group from a substrate molecule to ADP to form ATP, without involving the electron transport chain.

Oxidative Phosphorylation:ATP production driven by the electron transport chain and chemiosmosis. It accounts for the vast majority of ATP generated during aerobic respiration.

Proton Motive Force:The potential energy stored in the electrochemical gradient of protons across the inner mitochondrial membrane, used by ATP synthase to produce ATP.

Pyruvate:A three-carbon molecule produced by glycolysis. In aerobic conditions it is converted to acetyl-CoA; in anaerobic conditions it is reduced to lactate or ethanol.

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