Photosynthesis Vocabulary Review: Chloroplast Structure, Light Reactions, Calvin Cycle, and Pathways

Vocabulary flashcards covering key terms related to chloroplast structure, light-dependent reactions, the Calvin Cycle, and C3/C4/CAM photosynthesis.

Chloroplast

Double-membrane organelle in plant cells where photosynthesis occurs; contains thylakoids, granum, and stroma.

Granum

Stacks of thylakoids inside the chloroplast.

Thylakoid

Flattened membrane-bound sacs where the light-dependent reactions take place.

Thylakoid membrane

Membrane enclosing the thylakoid lumen; site of the electron transport chain and photophosphorylation.

Thylakoid lumen

Internal space inside thylakoids where protons accumulate during electron transport.

Stroma

Fluid matrix surrounding thylakoids; location of the Calvin Cycle.

Stroma lamellae

Membrane extensions that connect grana; site of cyclic photophosphorylation.

PSII

Photosystem II; initiates light reactions and drives water splitting (P680).

P680

Reaction-center pigment of PSII absorbing at 680 nm.

PSI

Photosystem I; re-energizes electrons to form NADPH (P700).

P700

Reaction-center pigment of PSI absorbing at 700 nm.

Chlorophyll A

Primary pigment; magnesium-containing porphyrin ring; central to reaction centers.

Chlorophyll B

Accessory pigment that broadens light absorption."

Carotenoids

Accessory pigments that help broaden light capture and protect against photooxidation.

NADPH

Reducing power produced in the light reactions; used in the Calvin Cycle.

ATP

Energy currency produced during the light reactions; consumed in the Calvin Cycle.

RuBP

Ribulose-1,5-bisphosphate; 5-carbon CO2 acceptor in the Calvin Cycle.

RuBisCO

Ribulose-1,5-bisphosphate carboxylase/oxygenase; fixes CO2 to RuBP; can also fix O2.

PGA

3-phosphoglycerate; product of CO2 fixation by RuBisCO.

G3P

Glyceraldehyde-3-phosphate; 3-carbon sugar produced in the Calvin Cycle; precursor to glucose.

PGAL

Another name for G3P; used to synthesize carbohydrates.

Carboxylation

Calvin Cycle step: CO2 + RuBP to PGA, catalyzed by RuBisCO.

Reduction

Calvin Cycle step: PGA is reduced to G3P using ATP and NADPH.

Regeneration

Calvin Cycle step: Most G3P is used to regenerate RuBP with ATP.

Carbohydrate Synthesis

Remaining G3P is used to synthesize glucose.

Non-Cyclic Photophosphorylation

Electron flow from PSII to PSI producing ATP and NADPH with O2 evolution.

Cyclic Photophosphorylation

PSI-based cycle that generates ATP only; no NADPH produced.

Photolysis

Splitting of water at PSII to release electrons, protons, and O2.

Chemiosmosis

Movement of protons across the thylakoid membrane through ATP synthase to make ATP.

Action Spectrum

Pattern of photosynthetic efficiency across wavelengths; chloroplasts absorb red and blue best, green is reflected.

C4 Photosynthesis

CO2 fixed in mesophyll cells to form a 4-carbon compound; transferred to bundle sheath cells to reduce photorespiration and water loss; requires extra ATP.

CAM Photosynthesis

Temporal separation: CO2 fixed at night into 4-carbon compounds; stored and released during day to reduce water loss.

Photorespiration

RuBisCO fixes O2 instead of CO2, reducing photosynthetic efficiency.

Calvin Cycle

Light-independent reactions in the stroma that fix CO2 into carbohydrates using ATP and NADPH; regenerates RuBP.

Glucose

Final carbohydrate product formed from G3P after the Calvin Cycle.