Photosynthesis

Front 1

Absorption Spectrum

Back 1

the range of a pigment's ability to absorb various wavelenghs of light

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Action Spectrum

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a profile of the relative performance of different wavelenghts of light

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Autotroph

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an organism that obtains organic food molecules without eating other organisms or substances derived from other organisms; use energy from the sun or from the oxidation of inorganic substances to make organic moleculse from inorganic ones

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Bundle-Sheath Cell

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a type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf

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C3 Plant

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a plant that uses the Calvin Cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate

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C4 Plant

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a plant that prefaces the Calvin Cycle with reactions that incorporate CO2 into four-carbon compounds, the end product of which supplies CO2 for the Calvin Cycle

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Calvin Cycle

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the second of two major stages in photosynthesis (following the light reactions), involving atmospheric CO2 fixation and reduction of the fixed carbon into carbohydrate

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CAM Plant

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a plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions, first discovered in the family Crassulaceae. Carbon dioxide entering open stomata during the night is converted into organic acids, which release CO2 for the Calvin Cycle during the day, when stomata are closed

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Carbon Fixation

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the incorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic bacterium)

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Cartenoids

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an accessory pigment, either yellow or orange, in the chlorophasts of plants; by absorbing wavelenghts of light that chlorophyll cannot, they broaden the spectrum of colors that can drive photosynthesis

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Chlorophyll A

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a type of blue-green photosynthetic pigment that participates directly in the light reaction

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Chlorophyll B

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a type of yellow-green accessory photosynthetic pigment that transfers energy to chlorophyll a

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Crassulacean Acid Metabolism (CAM)

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a type of metabolism in which carbon dioxide is taken in at night and incorporated into a variety of organic acids

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Cyclic Electron Flow

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a route of electron flow during the light reactions of photosynthesis that involves only photosystem I and that produces ATP but not NADPH or oxygen

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Cyclic Photophosphorylation

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the generation of ATP by cyclic electron flow

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Glyceraldehyde-3-Phosphate (G3P)

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the carbohydrate produced directly from the Calvin Cycle

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Heterotroph

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an organism that obtains organic food molecules by eating other organisms or their by-products

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Light Reactions

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the steps in photosynthesis that occur on the thlakoid membranes of the chloroplast and that convert solar energy to the chemical energy of ATP and NADPH, evolving oxygen in the process

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Mesophyll

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the ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis

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NADP+

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an acceptor that temporarily stores energized electrons produced during the light reactions

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Noncyclic Photophosphorylation

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the production of ATP by noncyclic electron flow, a route of electron flow during the light reactions of photosynthesis that involves both photosystems and produces ATP, NADPH, and oxygen. The net electron flow is from water to NADP+

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Photon

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a quantum, or discrete amount, of light energy

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Photorespiration

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a metabolic pathway that consumes oxygen, releases carbon dioxide, generates no ATP, and decreases photosynthetic output; generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide

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Photosynthesis

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the conversation of light energy to chemical energy that is stored in glucose or other organic compounds; occurs in plants, algae, and certain prokaryotes

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Photosystem I

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one of two light-harvesting units of a chloroplast's thylakoid membrane; it uses the P700 reaction-center chlorophyll

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Photosystem II

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one of two light-harvesting units of a chloroplast's thylakoid membrane; it uses the P680 reaction-center chlorophyll

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Reaction Center

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the chlorophyll a molecule and the primary electron acceptor in a photosystem; they trigger the light reactions of photosynthesis; the chlorophyll donates an electron, excited by light energy, to the primary electron acceptor, which passes an electron to an electron transport chain

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Rubisco

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ribulose carboxylase, the enzyme that catalyzes the first step of the Calvin Cycle (the addition of CO2 to RuBP, or ribulose bisphosphate)

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Stoma

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a microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant