Ch 6: Metabolism–Fueling Cell Growth (Flashcards)

Vocabulary flashcards covering metabolism, energy production, pathways, enzymes, respiration, fermentation, chemolithotrophy, and photosynthesis as described in the lecture notes.

Metabolism

Sum of all chemical reactions in a cell, including biosynthesis (anabolism) and energy harvesting (catabolism).

Biosynthesis

Anabolic processes that synthesize new cellular components; requires energy from ATP.

Catabolism

Degradative reactions that break down molecules to harvest energy (ATP).

Anabolism

Reactions that build cell components; require energy and use energy produced by catabolism.

Exergonic reaction

A reaction that releases free energy and typically proceeds spontaneously.

Endergonic reaction

A reaction that requires input of free energy; products have higher free energy.

Free energy

Energy available to do work in a reaction (Gibbs free energy).

Activation energy

Energy required to start a reaction; enzymes lower this barrier.

Enzyme

Biological catalyst that speeds a reaction without being consumed or altered; highly specific.

Substrate

Molecule acted upon by an enzyme.

Suffix -ase

Enzyme name suffix (e.g., protease, nuclease, lipase).

Cofactor

Non-protein component that assists an enzyme; often a trace element.

Coenzyme

Organic cofactor that carries molecules or electrons (e.g., NAD+, FAD, NADP+).

NAD+

Nicotinamide adenine dinucleotide, oxidized form; accepts electrons to become NADH.

NADH

Reduced form of NAD+; carries electrons, provides reducing power.

FAD

Flavin adenine dinucleotide, oxidized form; accepts electrons to become FADH2.

FADH2

Reduced form of FAD; carries electrons to the electron transport chain.

NADP+

Nicotinamide adenine dinucleotide phosphate; electron carrier used in anabolic reactions.

ATP

Adenosine triphosphate; main energy currency of the cell; allosteric energy carrier.

Substrate phosphorylation

Direct transfer of a phosphate to ADP to form ATP during glycolysis or TCA.

Oxidative phosphorylation

ATP synthesis driven by the proton motive force generated by the electron transport chain.

Photophosphorylation

ATP synthesis driven by light energy (photosynthesis).

Glycolysis

Pathway that oxidizes glucose to pyruvate; net gain of 2 ATP and 2 NADH per glucose.

Embden-Meyerhof pathway

Another name for glycolysis (the classic glycolytic pathway).

Entner-Doudoroff pathway

Alternative glycolytic pathway in some bacteria; yields pyruvate with less ATP.

Pentose phosphate pathway

PPP; produces NADPH and ribose-5-phosphate for biosynthesis; works with glycolysis.

Pyruvate

End product of glycolysis; converted to acetyl-CoA in the transition step.

Transition step

Pyruvate to acetyl-CoA; generates NADH and links glycolysis to the TCA cycle.

Acetyl‑CoA

Central metabolite; input to the TCA cycle and donor for fatty acids and cholesterol synthesis.

Krebs cycle / TCA cycle

Completes oxidation of acetyl‑CoA to CO2; yields ATP (or GTP), NADH, and FADH2.

Electron transport chain

Series of membrane-bound carriers that transfer electrons, pumping protons to generate PMF.

Proton motive force

Proton gradient across a membrane that drives ATP synthase to produce ATP.

ATP synthase

Enzyme that uses PMF to synthesize ATP from ADP and Pi.

Aerobic respiration

Respiration using O2 as the terminal electron acceptor to maximize ATP yield.

Anaerobic respiration

Respiration using inorganic molecules other than O2 as terminal electron acceptors.

Fermentation

ATP production via glycolysis only; regenerates NAD+ by using pyruvate as terminal acceptor.

Lactic acid fermentation

Fermentation where pyruvate is reduced to lactate; NAD+ is regenerated.

Ethanol fermentation

Fermentation where pyruvate is converted to ethanol and CO2; NAD+ is regenerated.

Chemolithotrophs

Microorganisms that harvest energy from inorganic compounds (e.g., H2, NH3) via oxidative phosphorylation.

Photosynthesis

Process by which photosynthetic organisms harvest light energy to synthesize organic compounds from CO2.

Light-dependent reactions

Stage that converts light energy to chemical energy (ATP and NADPH); involves photosystems.

Calvin cycle

Light-independent stage that fixes CO2 into sugars using ATP and NADPH.

Carbon fixation

Incorporation of CO2 into organic molecules during the Calvin cycle.

Chlorophyll

Primary pigment for photosynthesis in plants, algae, and cyanobacteria.

Carotenoids

Accessory pigments that broaden light absorption; protect against damage.

Phycobilins

Accessory pigments found in cyanobacteria and some algae.

Photosystems

Protein complexes containing pigments that capture light and funnel energy to reaction centers.

Reaction center

Pigment core that donates electrons to an electron transport chain.

Antennae pigments

Pigments that collect light energy and transfer it to reaction centers.

Stroma

Fluid within chloroplasts where the Calvin cycle occurs; contains DNA, RNA, ribosomes.

Thylakoid

Membranous sacs where photosystems and the light reactions take place.

Oxygenic photosynthesis

Photosynthesis that produces O2 as a byproduct (uses water as electron donor).

Anoxygenic photosynthesis

Photosynthesis that does not produce O2 (uses other electron donors).

Ribulose-1,5-bisphosphate

CO2 acceptor in the Calvin cycle; combines with CO2 to start carbon fixation.

3-phosphoglycerate

First stable product of CO2 fixation in the Calvin cycle; precursor to sugars.

Glyceraldehyde-3-phosphate

A triose phosphate formed during the Calvin cycle; used to synthesize glucose.

Precursor metabolites

Basic building blocks (e.g., pyruvate, acetyl‑CoA, oxaloacetate) feeding anabolic pathways.

Nucleotide synthesis

Synthesis of nucleotides; ribonucleotides created first, then converted to deoxyribonucleotides.