Photosynthesis and ATP Synethesis - pt 1

Vocabulary flashcards covering key terms related to photosynthesis, leaf structure, chloroplasts, pigments, and spectra.

Photosynthesis

Process by which light energy from the sun is converted into chemical energy (ATP) and used to synthesize carbohydrates in green plants; occurs mainly in leaves with chloroplasts and chlorophyll; energy in products exceeds energy in reactants.

Chloroplast

Organelle where photosynthesis occurs; double membrane; contains stroma, thylakoids, and granum; site of light-dependent and light-independent reactions; oriented 90° to light.

Chlorophyll

Green pigment in chloroplasts that absorbs red, blue, and violet light to drive photosynthesis; most common pigment is chlorophyll-a; leaf green results from reflecting green light.

Chlorophyll-a

Most abundant chlorophyll; common to all plants; directly participates in the light reactions of photosynthesis.

Palisade mesophyll

Major site of photosynthesis in leaves; tall columnar cells packed with many chloroplasts; arranged to maximize light absorption; chloroplasts can move for optimum light capture.

Spongy mesophyll

Irregularly shaped cells with large intercellular air spaces to facilitate gas diffusion; contains some chloroplasts.

Guard cell

Epidermal cells containing chloroplasts that regulate stomatal opening and closing through turgor changes.

Stomata

Pores in the leaf epidermis surrounded by guard cells; allow gas exchange (CO2 in, O2 out) and water vapor diffusion; openings controlled by guard cells.

Cuticle

Waxy layer secreted by the epidermis (cutin) that reduces water loss by evaporation; can be thickened in xerophytes; usually transparent to light.

Upper epidermis

Outer leaf layer, usually one or two cells thick; protects against water loss and allows light penetration.

Lower epidermis

Bottom leaf layer; contains stomata and guard cells; cuticle often thinner than upper epidermis.

Xylem

Tissue that transports water and mineral salts from roots to leaves; reinforced by lignified walls.

Phloem

Tissue that transports products of photosynthesis (mainly sucrose) and other solutes throughout the plant.

Thylakoid

Membranous sacs inside chloroplasts; stacked into grana; site of light-dependent reactions; contain photosynthetic pigments.

Granum (grana)

Stacks of thylakoids; major site of light-dependent reactions.

Stroma

Fluid-filled matrix of the chloroplast; site of light-independent reactions (Calvin cycle); contains enzymes, starch grains, lipid droplets, ribosomes, and circular DNA.

Calvin cycle

Series of light-independent reactions in the stroma that synthesize sugars using CO2 and ATP/NADPH produced in the light reactions.

Phototropism

Growth response where shoots bend toward light to maximize light exposure for photosynthesis.

Accessory pigments

Pigments such as chlorophyll-b, chlorophyll-c/d, and carotenoids that transfer absorbed energy to chlorophyll-a but do not themselves drive the light-dependent reactions.

Carotenoids

Accessory pigments including carotenes and xanthophylls; yellow, orange, and brown pigments that absorb blue-violet light and protect chlorophyll from excess light.

Carotenes

Type of carotenoid that is hydrocarbon-based; absorbs blue light and contributes to yellow-orange coloration.

Xanthophylls

Oxygen-containing carotenoids; yellow pigments that assist in light capture and photoprotection.

Absorption spectrum

Graph showing the relative absorption of different wavelengths of light by a pigment.

Action spectrum

Graph showing the effectiveness of different wavelengths in stimulating photosynthesis.

Photon

A quantum of light energy; energy per photon increases as wavelength decreases (shorter wavelengths have higher energy).