AP BIO CHAPTER 10

Autotroph / Photoautotroph

Autotrophs make their own food; photoautotrophs use sunlight to do it.

Heterotroph

An organism that must get food by eating other organisms.

Chloroplast

The organelle where photosynthesis happens.

Stomata

Small openings on leaves that let CO₂ in and O₂ + water vapor out.

Thylakoid Membrane; Thylakoid Space

The membrane where the light reactions occur; the space inside the thylakoid discs.

Grana (Granum)

Stacks of thylakoids inside the chloroplast.

Stroma

The fluid-filled area around the thylakoids where the Calvin cycle happens.

Light Reactions

The first stage of photosynthesis that uses light to make ATP and NADPH.

Calvin Cycle

The set of reactions that uses ATP and NADPH to build sugar (G3P) from CO₂.

NADP⁺ / NADPH

Electron carrier pair; NADP⁺ accepts electrons to become NADPH, which carries energy to the Calvin cycle.

Photophosphorylation

Making ATP using light energy (during the light reactions).

Carbon Fixation

The process of turning CO₂ into organic molecules during the Calvin cycle.

Chlorophyll a & b; Carotenoids

Pigments that absorb light; chlorophylls absorb mostly blue/red, carotenoids absorb extra wavelengths and protect the plant.

Noncyclic (“Linear”) / Cyclic Electron Flow

Linear makes both ATP and NADPH; cyclic makes only ATP.

Photosystems II & I (P680 & P700)

Light-harvesting complexes that absorb light; PSII uses P680, PSI uses P700.

Primary Electron Acceptor

A molecule in the photosystem that catches excited electrons from chlorophyll.

RuBP

A 5-carbon sugar that CO₂ attaches to at the start of the Calvin cycle.

G3P

A 3-carbon sugar made by the Calvin cycle; one G3P can help build glucose.

C3, C4, CAM Plants

C3 use normal Calvin cycle; C4 separate steps by space; CAM separate steps by time to reduce water loss.

Photorespiration

A wasteful process where rubisco binds O₂ instead of CO₂, reducing sugar production.

Mesophyll / Bundle-Sheath Cells

Mesophyll = main photosynthetic cells; bundle-sheath = deeper cells used in C4 plants for carbon fixation.

Rubisco

The enzyme that adds CO₂ to RuBP in the Calvin cycle (but can also bind O₂).

PEP Carboxylase

An enzyme in C4 and CAM plants that captures CO₂ efficiently and does not bind O₂.