Cellular Respiration and Glycolysis

Vocabulary flashcards covering catabolic pathways, redox reactions, cellular respiration stages, and glycolysis steps based on lecture notes.

Catabolic pathway

A metabolic pathway that breaks down a large, energy-rich molecule into smaller, lower-energy molecules, such as breaking down glucose into $\text{CO}_2$ and $\text{H}_2\text{O}$.

Aerobic respiration

A cellular respiration pathway used by most eukaryotic cells and many prokaryotes that uses an electron transport chain and oxygen as the final electron acceptor, producing about $30\text{--}32\text{ ATP}$ per glucose.

Anaerobic respiration

A respiration pathway in certain prokaryotes that uses an electron transport chain with a final electron acceptor other than oxygen, such as sulfate.

Fermentation

An anaerobic process that does not use oxygen or an electron transport chain, producing only $2\text{ ATP}$ per glucose to regenerate $\text{NAD}^+$ so glycolysis can continue.

Oxidation

The loss of electrons from a substance during a redox reaction.

Reduction

The gain of electrons by a substance during a redox reaction.

Reducing agent

An electron donor in a redox reaction that causes another substance to be reduced while becoming oxidized itself.

Oxidizing agent

An electron acceptor in a redox reaction that causes another substance to be oxidized while becoming reduced itself.

$$\text{NAD}^+$$

The oxidized form of the electron carrier that acts as an oxidizing agent by accepting two electrons and one proton during cellular respiration.

NADH

The reduced form of the electron carrier that holds high-energy electrons and delivers them to the electron transport chain.

Electron transport chain (ETC)

A group of electron-carrying molecules in the inner mitochondrial membrane of eukaryotes (or plasma membrane of prokaryotes) that passes electrons to lower-energy states to pump $\text{H}^+$ ions.

Substrate-level phosphorylation

A mode of ATP synthesis where an enzyme directly transfers a phosphate group from an organic substrate molecule to ADP.

Oxidative phosphorylation

A process consisting of electron transport and chemiosmosis where an $\text{H}^+$ gradient powers ATP synthase to produce almost $90\text{\%}$ of ATP in aerobic respiration.

Glycolysis

A ten-step cytosol process that splits one six-carbon glucose into two three-carbon pyruvate molecules without using oxygen, yielding a net of $2\text{ ATP}$ and $2\text{ NADH}$.

Energy investment phase

The first phase of glycolysis in which the cell spends $2\text{ ATP}$ to phosphorylate glucose and prepare it to split.

Energy payoff phase

The second phase of glycolysis where $4\text{ ATP}$, $2\text{ NADH}$, and $2\text{ pyruvate}$ are produced, yielding a net gain of $2\text{ ATP}$.

Hexokinase

The enzyme that catalyzes Step 1 of glycolysis by transferring a phosphate group from ATP to glucose, producing glucose 6-phosphate.

Phosphofructokinase (PFK)

The key regulatory enzyme in Step 3 of glycolysis that transfers a phosphate from ATP to fructose 6-phosphate, committing the molecule to glycolysis.

Phosphoenolpyruvate (PEP)

A high-energy intermediate formed in Step 9 of glycolysis that donates its phosphate group to ADP in Step 10 to form ATP and pyruvate.

Pyruvate oxidation

The stage of cellular respiration occurring in the mitochondrial matrix of eukaryotes where pyruvate is converted into acetyl CoA.

Citric acid cycle

The stage of cellular respiration occurring in the mitochondrial matrix of eukaryotes where acetyl CoA is oxidized to $\text{CO}_2$.