Chapter 21 Photosynthesis – Supplementary Notes (VOCABULARY Flashcards)

Key vocabulary terms and concise definitions covering the major concepts, structures, pigments, and processes involved in photosynthesis as presented in the notes.

Photosynthesis

The process by which green plants, algae, and certain bacteria convert light energy, CO2 and water into chemical energy (glucose), releasing oxygen as a by-product.

Chloroplast

Plant cell organelle where photosynthesis occurs; contains chlorophyll, thylakoids, granum, and stroma.

Chlorophyll

Green pigment that absorbs blue and red light, driving the light-dependent reactions of photosynthesis.

Thylakoid

Disc-shaped membrane-bound sacs inside chloroplasts where the light-dependent reactions take place.

Granum (plural: grana)

A stack of thylakoids within the chloroplast; increases surface area for light absorption.

Stroma

Fluid-filled interior of a chloroplast where the Calvin cycle (light-independent reactions) occurs.

Light-dependent reactions

Stage of photosynthesis in the thylakoid membranes that uses light to produce ATP and NADPH and release O2.

Light-independent reactions (Calvin cycle)

Stage set in the stroma that uses ATP and NADPH to fix CO2 into carbohydrates.

Photolysis of water

Splitting of water by light energy during the light reactions to provide electrons, protons, and O2.

NADP+/NADPH

Nicotinamide adenine dinucleotide phosphate; NADP+ accepts electrons to form NADPH, a reducing agent for carbon fixation.

ATP

Adenosine triphosphate; energy currency produced during the light reactions to power the Calvin cycle.

RuBP (Ribulose-1,5-bisphosphate)

Five-carbon compound that acts as the CO2 acceptor in the Calvin cycle.

GP (Glycerate-3-phosphate)

Three-carbon intermediate formed when CO2 is fixed to RuBP during the Calvin cycle.

TP (Triose phosphate, PGAL/GAP)

Three-carbon sugar produced in the Calvin cycle; used to synthesize carbohydrates and regenerate RuBP.

Calvin cycle

Light-independent cycle in the stroma that fixes CO2 into carbohydrates using ATP and NADPH.

Carbohydrates (in photosynthesis context)

Sugars and starches produced from triose phosphates; include glucose, sucrose, and starch.

Glucose

A simple sugar produced from TP; a key carbohydrate for respiration and biosynthesis.

Sucrose

Disaccharide formed from glucose; transported through phloem to parts of the plant.

Starch

Storage polysaccharide formed from glucose, stored mainly in leaves when not immediately needed.

Cellulose

Structural polysaccharide synthesized from glucose; main component of plant cell walls.

Lipids

Fatty acids and glycerol derived from TP; used for membrane formation and energy storage.

Proteins

Macromolecules built from amino acids derived from GP/TP; used for enzymes, membranes, and growth.

Stomata

Pores in the leaf epidermis that regulate gas exchange (CO2 in, O2 out) and water loss.

Guard cells

Pair of cells surrounding a stomatal pore that control its opening and closing.

Cuticle

Waxy outer layer that reduces water loss from the leaf surface.

Epidermis

Outer protective cell layer of the leaf; can be transparent to allow light in.

Palisade mesophyll

Layer of tall, closely packed cells rich in chloroplasts; main site of photosynthesis.

Spongy mesophyll

Leaf layer with air spaces facilitating gas diffusion and photosynthesis.

Xylem

Vascular tissue that transports water and minerals from roots to leaves.

Phloem

Vascular tissue that transports sugars and nutrients from leaves to other parts of the plant.

Absorption spectrum

Graph showing which wavelengths of light are absorbed by pigments (e.g., chlorophyll).

Action spectrum

Graph showing the rate of photosynthesis at different wavelengths; often aligns with pigment absorption.

Destarching

Process of removing stored starch from a plant (usually by keeping in the dark) before experiments.

DCPIP test

Chemical test using DCPIP dye to indicate oxygen production during photosynthesis by a color change and/or reduction.

18O labeling

Use of the heavy oxygen isotope to trace the source of oxygen in the O2 produced during photosynthesis.

18O2 vs 16O2

Different isotopes used to determine whether O2 comes from water or CO2 in photosynthesis experiments.

RuBP regeneration

Part of the Calvin cycle where TP is used to regenerate RuBP to continue CO2 fixation.

Carbon fixation

Initial incorporation of CO2 into a five-carbon sugar (RuBP) to form a 6-carbon intermediate that splits into GP.

GP to TP reduction

GP is reduced to TP using ATP and NADPH in the Calvin cycle.

Photosynthetic pigments

Molecules like chlorophyll and carotenoids that absorb light and drive photosynthesis.

Carotenoids

Accessory pigments that broaden the spectrum of light absorbed and protect against light damage.