Chapter 8 - Principals of Biology

Photosynthesis

Process, usually occurring within chloroplasts, that uses solar energy to reduce carbon dioxide to carbohydrate.

autotrophs

Organism that can capture energy and synthesize organic molecules from inorganic nutrients.

heterotrophs

Organism that cannot synthesize needed organic compounds from inorganic substances and therefore must take in organic food.

stomata

Small openings between two guard cells on the underside of leaf epidermis, through which gases pass.

chloroplast

Membrane-bound organelle in algae and plants with chlorophyll-containing membranous thylakoids; where photosynthesis takes place.

chlorophyll

Green photosynthetic pigment of algae and plants that absorbs solar energy; occurs as chlorophyll a and chlorophyll b.

carotenoid

An accessory photosynthetic pigment of plants and algae that are often yellow or orange in color; consists of two classes—the xanthophylls and the carotenes.

What is the equation for photosyntheis?

6 CO2 + 6H2O --> C6H12O6 + 6O2

light reactions

Portion of photosynthesis that captures solar energy and takes place in thylakoid membranes of chloroplasts; it produces ATP and NADPH.

calvin cycle reaction

Portion of photosynthesis that takes place in the stroma of chloroplasts and can occur in the dark. It uses the products of the light reactions to reduce CO2 to a carbohydrate.

NADP+ (nicotinamide adenine dinucleotide phosphate)

Coenzyme in oxidation-reduction reactions that accepts electrons and hydrogen ions to become NADPH + H+. During photosynthesis, NADPH participates in the reduction of carbon dioxide to a carbohydrate.

noncyclic electron pathway

Light-dependent photosynthetic pathway that is used to generate ATP and NADPH. Because the pathway is noncyclic, the electrons must be replaced by the splitting of water (photolysis).

photosystem

Photosynthetic unit where solar energy is absorbed and high-energy electrons are generated; contains a pigment complex and an electron acceptor; occurs as PS (photosystem) I and PS II.

ATP synthase

Complex of proteins in the cristae of mitochondria and thylakoid membrane of chloroplasts that produces ATP from the diffusion of hydrogen ions across a membrane.

cyclic electron pathway

Alternate form of the light-dependent reactions in photosynthesis that does not produce NADPH.

carbon dioxide fixation

Process by which carbon dioxide gas is attached to an organic compound; in photosynthesis, this occurs in the Calvin cycle reactions.

RuBP carboxylase

An enzyme that starts the Calvin cycle reactions by catalyzing attachment of the carbon atom from CO2 to RuBP.

C4 Plant

Plant that fixes carbon dioxide to produce a C4 molecule that releases carbon dioxide to the Calvin cycle.

CAM

Crassulacean-acid metabolism; a form of photosynthesis in succulent plants that separates the light-dependent and Calvin reactions by time.