Cellular Respiration and Photosynthesis Vocabulary Review

This set of flashcards focuses on the key vocabulary terms related to cellular respiration and photosynthesis, providing definitions and explanations for each term.

Cellular respiration

Metabolic process that breaks down glucose using oxygen to produce ATP, CO₂, and H₂O.

Fermentation

Anaerobic process of breaking down glucose to generate ATP without oxygen, producing by-products like ethanol or lactic acid.

Redox reaction

Chemical reaction involving the transfer of electrons; oxidation = loss of electrons, reduction = gain of electrons.

NAD⁺ / NADH

Nicotinamide adenine dinucleotide; NAD⁺ is the oxidized form (electron carrier), NADH is the reduced form that donates electrons.

Glycolysis

First step of cellular respiration; occurs in the cytosol; glucose is split into two pyruvate molecules, producing ATP and NADH.

Pyruvate

Three-carbon end product of glycolysis; can enter fermentation or be converted into acetyl CoA for respiration.

Acetyl CoA

Two-carbon molecule bound to coenzyme A that enters the citric acid cycle.

Citric acid cycle (Krebs cycle)

Metabolic cycle in the mitochondrial matrix that oxidizes acetyl CoA to CO₂, generating NADH, FADH₂, and ATP.

Substrate-level phosphorylation

Direct formation of ATP by transferring a phosphate group to ADP from a high-energy intermediate.

Oxidative phosphorylation

ATP synthesis powered by the electron transport chain and chemiosmosis.

Electron transport chain (ETC)

Series of protein complexes in the inner mitochondrial membrane that transfer electrons, releasing energy to pump protons.

Chemiosmosis

Process in which stored proton gradient energy is used to drive ATP synthesis.

Proton-motive force

Electrochemical gradient of protons across a membrane that powers ATP synthase.

ATP synthase

Enzyme that uses the proton-motive force to synthesize ATP from ADP and inorganic phosphate.

Obligate anaerobe

Organism that cannot survive in the presence of oxygen and relies on anaerobic metabolism.

Photosynthesis

Process by which plants, algae, and some prokaryotes convert light energy into chemical energy stored in sugars.

Autotroph

Organism that produces its own food from inorganic molecules (e.g., plants).

Heterotroph

Organism that must consume other organisms for energy and carbon.

Photoautotroph

Autotroph that uses light as its energy source (e.g., plants, algae).

Chloroplast

Plant organelle where photosynthesis occurs; contains thylakoids, grana, and stroma.

Thylakoid

Membrane sac inside chloroplasts where light reactions occur; stacked into grana; surrounding fluid is the stroma.

Light reactions

First stage of photosynthesis; convert solar energy to ATP and NADPH; release O₂ from water splitting.

Calvin cycle

Second stage of photosynthesis; uses ATP and NADPH to fix CO₂ into sugars.

NADP⁺ / NADPH

Electron carrier in photosynthesis; NADP⁺ is oxidized, NADPH is reduced and provides electrons for the Calvin cycle.

Photophosphorylation

ATP formation powered by light-driven electron flow.

Photosystem II (PSII/P680)

Protein complex that absorbs light, splits water, and initiates electron flow.

Photosystem I (PSI/P700)

Protein complex that absorbs light and boosts electrons to reduce NADP⁺ to NADPH.

Linear electron flow

Primary electron pathway that produces ATP, NADPH, and O₂.

Cyclic electron flow

Alternative pathway around PSI that produces ATP but not NADPH or O₂.

Carbon fixation

Incorporation of CO₂ into an organic molecule during the Calvin cycle.

Rubisco

Enzyme that catalyzes carbon fixation by attaching CO₂ to RuBP.

Photorespiration

Process where rubisco fixes O₂ instead of CO₂, consuming ATP and reducing photosynthetic efficiency.