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51 Cards in this Set

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absorption spectrum

The amount of light of different wavelengths absorbed by a pigment. Usually depicted as a graph of light absorbed versus wavelength.

action spectrum

The relative effectiveness of different wavelengths of light in driving a light-dependent process such as photosynthesis. Usually depicted as a graph of some measure of the process versus wavelength.

anoxygenic

Referring to any process or reaction that does not produce oxygen. Photosynthesis in purple sulfur and purple nonsulfur bacteria, which does not involve photosystem II, is anoxygenic.

antenna complex

Part of a photosystem, containing an array of chlorophyll molecules and accessory pigments, that receives energy from light and directs the energy to a central reaction center during photosynthesis.

autotroph

Any organism that can synthesize reduced organic compounds from simple inorganic sources such as CO2 or CH4. Most plants and some bacteria and archaea are autotrophs. Also called primary producer.

bundle-sheath cell

A type of cell found around the vascular tissue (veins) of plant leaves.

C3 photosynthesis

The most common form of photosynthesis in which atmospheric CO2 is used to form 3-phosphoglycerate, a three-carbon sugar.

Calvin cycle/reactions

In photosynthesis, the set of light-independent reactions that use NADPH and ATP formed in the light-dependent reactions to drive the fixation of atmospheric CO2 and reduction of the fixed carbon, ultimately producing sugars. Also calledcarbon fixation and light-independent reactions.

carbon fixation

Calvin Cycle.

carotenoid

Any of a class of accessory pigments, found in chloroplasts, that absorb wavelengths of light not absorbed by chlorophyll; typically appear yellow, orange, or red. Includes carotenes and xanthophylls.

chlorophyll

Any of several closely related green pigments, found in chloroplasts and photosynthetic protists, that absorb light during photosynthesis.

chloroplast

A chlorophyll-containing organelle that is bounded by a double membrane and in which photosynthesis occurs; found in most plant and algal cells. Also the location of amino acid, fatty acid, purine, and pyrimidine synthesis.

cyclic photophosphorylation

Path of electron flow during the light-dependent reactions of photosynthesis in which photosystem I transfers excited electrons back to the electron transport chain of photosystem II, rather than to NADP+. Also called cyclic electron flow.

electromagnetic spectrum

The entire range of wavelengths of radiation extending from short wavelengths (high energy) to long wavelengths (low energy). Includes gamma rays, x-rays, ultraviolet, visible light, infrared, microwaves, and radio waves (from short to long wavelengths).

ferredoxin

In photosynthetic organisms, an iron- and sulfur-containing protein in the electron transport chain of photosystem I. Can transfer electrons to the enzyme NADP+reductase, which catalyzes formation of NADPH.

fluorescence

The spontaneous emission of light from an excited electron falling back to its normal (ground) state.

glyceraldehyde-3-phosphate (G3P)

The phosphorylated three-carbon compound formed as the result of carbon fixation in the first step of the Calvin cycle.

granum

In chloroplasts, a stack of flattened, membrane-bound vesicles (thylakoids) where the light reactions of photosynthesis occur.

guard cells

One of two specialized, crescent-shaped cells forming the border of a plant stoma. Guard cells can change shape to open or close the stoma.

light-independent reactions

Calvin Cycle.

lumen

The interior space of any hollow structure (e.g., the rough ER) or organ (e.g., the stomach).

maladaptive

A trait that lowers fitness.

mesophyll cell

A type of cell, found near the surfaces of plant leaves, that is specialized for the light-dependent reactions of photosynthesis.

NAD+/NADH
Nicotinamide adenine dinucleotide exists in two forms, an oxidized and reduced form abbreviated as NAD+ and NADH respectively. In metabolism, nicotinamide adenine dinucleotide is involved in redox reactions, carrying electrons from one reaction to another.
nicotinamide adenine dinucleotide phosphate (NADP+/NADPH)

Oxidized and reduced forms, respectively, of nicotinamide adenine dinucleotide phosphate. A nonprotein electron carrier that is reduced during the light-dependent reactions in photosynthesis and extensively used in biosynthetic reactions.

noncyclic electron flow

Z scheme.

oxygenic

Referring to any process or reaction that produces oxygen. Photosynthesis in plants, algae, and cyanobacteria, which involves photosystem II, is oxygenic.

PEP carboxylase

An enzyme that catalyzes addition of CO2 to phosphoenol pyruvate, a three-carbon compound, forming a four-carbon organic acid. Found in mesophyll cells of plants that perform C4 photosynthesis.

pheophytin

In photosystem II, a molecule that accepts excited electrons from a reaction center chlorophyll and passes them to an electron transport chain.

photon

A discrete packet of light energy; a particle of light.

photophosphorylation

Production of ATP molecules using the energy released as light-excited electrons flow through an electron transport chain during photosynthesis. Involves generation of a proton-motive force during electron transport and its use to drive ATP synthesis.

photorespiration

A series of light-driven chemical reactions that consumes oxygen and releases carbon dioxide, basically reversing photosynthesis. Usually occurs when there are high O2 and low CO2 concentrations inside plant cells, often in bright, hot, dry environments when stomata must be kept closed.

photosynthesis

The complex biological process that converts the energy of light into chemical energy stored in glucose and other organic molecules. Occurs in plants, algae, and some bacteria.

photosystem

One of two types of units, consisting of a central reaction center surrounded by antenna complexes, that is responsible for the light-dependent reactions of photosynthesis.

photosystem I

A photosystem that contains a pair of P700 chlorophyll molecules and uses absorbed light energy to produce NADPH.

photosystem II

A photosystem that contains a pair of P680 chlorophyll molecules and uses absorbed light energy to split water into protons and oxygen and to produce ATP.

pigment

Any molecule that absorbs certain wavelengths of visible light and reflects or transmits other wavelengths.

plastocyanin

A small protein that shuttles electrons from photosystem II to photosystem I during photosynthesis.

plastoquinone

A nonprotein electron carrier in the chloroplast electron transport chain. Receives excited electrons from pheophytin and passes them to more electronegative molecules in the chain. Also carries protons to the lumen side of the thylakoid membrane, generating a proton-motive force.

reaction center

Centrally located component of a photosystem containing proteins and a pair of specialized chlorophyll molecules. Is surrounded by antenna complexes and receives excited electrons from them.

ribulose biphosphate (RuBP)

A five-carbon compound that combines with CO2 in the first step of the Calvin cycle during photosynthesis.

rubisco

The enzyme that catalyzes the first step of the Calvin cycle during photosynthesis: the addition of a molecule of CO2 to ribulose bisphosphate.

starch

A mixture of two storage polysaccharides, amylose and amylopectin, both formed from a-glucose monomers. Amylopectin is branched, and amylose is unbranched. The major form of stored carbohydrate in plants.

stoma

Generally, a pore or opening. In plants, a microscopic pore on the surface of a leaf or stem through which gas exchange occurs.

stroma

The fluid matrix of a chloroplast in which the thylakoids are embedded. Site where the Calvin cycle reactions occur.

sucrose

A disaccharide formed from glucose and fructose. One of the two main products of photosynthesis.

thylakoid

A flattened, membrane-bound vesicle inside a plant chloroplast that functions in converting light energy to chemical energy. A stack of thylakoids is a granum.

vascular tissue

In plants, any tissue that is involved in conducting water or solutes from one part of a plant to another.

visible light

The range of wavelengths of electromagnetic radiation that humans can see, from about 400 to 700 nanometers.

wavelength

The distance between two successive crests in any regular wave, such as light waves, sound waves, or waves in water.

Z scheme

Path of electron flow in which electrons pass from photosystem II to photosystem I and ultimately to NADP+ during the light-dependent reactions of photosynthesis.