Unit 3: Cellular Energetics — Metabolic Pathways & Survival

Cellular Respiration

Set of catabolic pathways that break down organic molecules to produce ATP.

ATP (Adenosine Triphosphate)

The 'energy currency' of the cell.

Exergonic

A reaction that releases energy, indicated by ΔG < 0.

REDOX reactions

Reduction-Oxidation reactions involved in energy transfer; oxidation is loss of electrons, reduction is gain.

Mnemonic for REDOX

OIL RIG (Oxidation Is Loss, Reduction Is Gain).

Glycolysis

The first step of cellular respiration that splits glucose into pyruvate.

Anaerobic

A process that does not require oxygen.

Pyruvate

A 3-carbon molecule formed from glucose during glycolysis.

Substrate-Level Phosphorylation

The direct production of ATP by transferring a phosphate group to ADP.

Net Yield of Glycolysis

Per glucose molecule, yields 2 ATP, 2 NADH, and 2 Pyruvate.

Pyruvate Oxidation

The conversion of pyruvate into Acetyl-CoA in the mitochondria.

Acetyl-CoA

A 2-carbon molecule formed from pyruvate during its oxidation.

Krebs Cycle (Citric Acid Cycle)

A metabolic cycle that completes the breakdown of glucose by processing Acetyl-CoA.

Oxidative Phosphorylation

The stage of cellular respiration where the majority of ATP is produced via the electron transport chain.

Electron Transport Chain (ETC)

A series of proteins in the mitochondrial membrane that transfer electrons and pump protons.

Proton Motive Force

The electrochemical gradient created by H+ ion concentration across the mitochondrial membrane.

ATP Synthase

An enzyme that uses the flow of protons to synthesize ATP from ADP and inorganic phosphate.

Final Electron Acceptor

Oxygen, which combines with electrons and protons to form water in the ETC.

Fermentation

A metabolic process that regenerates NAD+ by converting pyruvate in the absence of oxygen.

Alcohol Fermentation

A type of fermentation that produces ethanol and CO2, commonly used in brewing and baking.

Lactic Acid Fermentation

Fermentation that produces lactate, occurring in muscle cells and some bacteria.

Hemoglobin Variance

Different forms of hemoglobin that allow organisms to survive in varying oxygen levels.

Decoupling Oxidation from Phosphorylation

A process in which proton movement does not lead to ATP production, seen in thermogenesis.

Thermogenin

A protein that allows protons to leak back into the mitochondrial matrix without passing through ATP Synthase.

Heterotroph Isolation

The evolutionary fitness determined by unique metabolic pathways exploited by specific bacteria.

Common Mistake: Energy Creation

Energy is not created; it is transformed from glucose into ATP.

Common Mistake: Krebs Cycle Oxygen Usage

Oxygen is not directly used in the Krebs Cycle, but is crucial for the ETC.

Common Mistake: Fermentation ATP Production

Fermentation does not produce ATP; glycolysis does.