Ch 5: Cell Metabolism — Synthesis and Degradation of Biological Molecules (Vocabulary Flashcards)

Vocabulary flashcards covering key terms and concepts from metabolism, respiration, and photosynthesis as presented in the lecture notes.

ATP

Adenosine triphosphate; the cell’s energy currency; hydrolysis of its high‑energy phosphate bonds releases energy to drive endergonic reactions and is regenerated from ADP and Pi.

NADH

The reduced form of NAD⁺; carries electrons to the electron transport chain and is produced during glycolysis, pyruvate oxidation, and the citric acid cycle.

NAD+

The oxidized form of NAD; accepts electrons to become NADH in cellular redox reactions.

NADPH

The reduced form of NADP⁺; provides reducing power for biosynthetic reactions, notably in photosynthesis.

Redox reaction

A chemical reaction involving the transfer of electrons; oxidation and reduction occur in tandem.

Oxidation

Loss of electrons (or hydrogens) in a molecule; often associated with a decrease in chemical‑bond energy in the substrate.

Reduction

Gain of electrons (or hydrogens) by a molecule; often increases the energy stored in the product’s bonds.

Oxidative phosphorylation

Formation of ATP via energy released from electron transfers through the electron transport chain and the resulting proton gradient.

Electron transport chain

A series of membrane-bound protein complexes that transfer electrons and pump protons to create a proton gradient.

Chemiosmosis

The flow of protons down their gradient through ATP synthase to synthesize ATP.

Proton‑motive force

The electrochemical gradient of protons across a membrane that drives ATP synthesis.

ATP synthase

Rotary enzyme (FoF1) that uses the proton gradient to convert ADP and Pi into ATP.

Substrate‑level phosphorylation

Direct transfer of a phosphate from a substrate to ADP to form ATP, occurring in glycolysis and other steps.

Glycolysis

Cytosolic pathway that converts glucose to two pyruvate, yielding a net gain of ATP and NADH and producing intermediates for other pathways.

Pyruvate oxidation

Oxidation of pyruvate to acetyl‑CoA and CO₂ in the mitochondrial matrix, generating NADH and linking glycolysis to the citric acid cycle.

Acetyl‑CoA

Two‑carbon acetyl group donor that enters the citric acid cycle after being formed from pyruvate oxidation.

Citric acid cycle

Eight‑step cycle that fully oxidizes acetyl‑CoA to CO₂, producing NADH, FADH₂, and GTP; regenerates oxaloacetate.

FADH₂

Reduced form of FAD; acts as an electron carrier in respiration, delivering fewer protons across the membrane than NADH.

FAD

Oxidized form of FAD; accepts electrons to become FADH₂.

Pyruvate

End product of glycolysis; a three‑carbon molecule that is oxidized in aerobic respiration or reduced during fermentation.

Oxygen (O₂) as terminal electron acceptor

Final electron acceptor in aerobic respiration; reduction of O₂ to H₂O drives the electron transport chain.

Fermentation

Anaerobic process that regenerates NAD⁺ from NADH, enabling glycolysis to continue; produces lactate or ethanol with CO₂ and limited ATP.

Lactic acid fermentation

Fermentation where pyruvate is reduced to lactate, regenerating NAD⁺; occurs in muscles and many microbes.

Alcoholic fermentation

Fermentation where pyruvate is converted to ethanol and CO₂, regenerating NAD⁺; common in yeast.

Pyruvate dehydrogenase complex

Multienzyme complex that converts pyruvate to acetyl‑CoA in the mitochondrial matrix, producing NADH.

Oxaloacetate

Four‑carbon molecule that combines with acetyl‑CoA to form citrate in the citric acid cycle; regenerated each turn.

Citrate

Six‑carbon molecule formed from acetyl‑CoA and oxaloacetate; initiates the citric acid cycle.

GTP

Guanosine triphosphate; produced in the citric acid cycle and can be converted to ATP via phosphorylation.

Glucose

Six‑carbon sugar; primary substrate for glycolysis and central to cellular respiration.

Mitochondrial matrix

Internal space of mitochondria where pyruvate oxidation and the citric acid cycle occur.

Cytosol

Cell fluid where glycolysis and fermentation take place.

Photosynthesis

An anabolic process that converts light energy into chemical energy to fix CO₂ into carbohydrates and release O₂.

Chloroplast

Plant organelle where photosynthesis occurs; contains thylakoids and stroma.

Thylakoid

Membrane‑bound sacs inside chloroplasts where the light reactions take place.

Stroma

Fluid surrounding the thylakoids; site of the Calvin cycle.

Light reactions

First phase of photosynthesis that captures light energy to form ATP and NADPH in the thylakoid membranes.

Calvin cycle

Carbon fixation cycle in the chloroplast stroma that uses ATP and NADPH to convert CO₂ into sugars; regenerates RuBP.

Rubisco

Ribulose‑1,5‑bisphosphate carboxylase/oxygenase; fixes CO₂ to RuBP and can also fix O₂, leading to photorespiration.

RuBP

Ribulose‑1,5‑bisphosphate; CO₂ acceptor in the Calvin cycle, forming 3‑phosphoglycerate.

G3P

Glyceraldehyde‑3‑phosphate; three‑carbon sugar produced in the Calvin cycle and used to build sugars.

3PG

3‑phosphoglycerate; initial five‑to‑three carbon step product in the Calvin cycle.