Ap Biology: Photosynthesis

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absorption spectrum

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-The graph that expresses a pigment's absorption of various wavelengths of light.

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action spectrum

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-The graph that expresses the relationship between photosynthetic rate and absorption of various wavelengths of light

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autotroph

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-An organism that utilizes either photosynthesis or chemosynthesis to produce its own organic food from inorganic CO₂
-Kingdoms Plantae, Protista, and Eubacteria include such organisms

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Calvin cycle

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-The series of biochemical reactions that occur in the stroma and utilize carbon dioxide (CO₂) and ATP and NADPH from the light-independent reactions to produce glucose
-Fixes inorganic CO₂into organic glucose usable for energy by all organisms

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CAM plant

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-A plant that uses crassulacean acid metabolism, a specialized adaptation found in desert plants that allows for collection and storage of CO₂at night when water loss is minimized
-During the day, when stomata are closed, the CO₂is released from storage and used in the Calvin cycle

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carbon fixation

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-The process conducted by autotrophs during which inorganic CO₂molecules are converted into organic glucose molecules
-Responsible for the production of the organic molecules that heterotrophs depend on for food

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carotenoid

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-An accessory pigment of photosynthesis in plants and green algae
-Maximizes absorption in the region of the spectrum missed by the chlorophylls and reflects back yellow-orange wavelengths to the observer.

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chlorophyll a

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-The main pigment of photosynthesis in plants and algae
-Maximizes absorption in the red and blue wavelengths of the spectrum and reflects the green wavelengths back to the observer

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chlorophyll b

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-An accessory pigment of photosynthesis in plants and green algae
-Maximizes absorption in the red and blue wavelengths so as to complement the absorption of chlorophyll a

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C₃plant

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-A plant that directly incorporates CO₂into the Calvin cycle
-CO₂combines with five-carbon RuBP to produce a six-carbon intermediate, which immediately splits to the stable three-carbon G3P molecule used to build glucose and regenerate RuBP

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C₄plant

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-A plant that incorporates CO₂into a four-carbon compound and, ultimately, into the Calvin cycle
-Allows for increased water efficiency by highly regulating opening and closing of the stomata during the day

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cyclic electron flow

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-The movement of electrons during the light-dependent reactions that utilizes only photosystem I and produces additional ATP but no more NADPH or oxygen
-Helps reconcile the disproportionate amounts of ATP and NADPH used by the Calvin cycle

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electromagnetic spectrum

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-The spectrum of radiation based on the inverse relationship between wavelength and frequency
-Gamma rays possess the shortest wavelength, radio waves have the longest, and visible light expresses medium-length waves

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glyceraldehyde-3-phosphate (G3P)

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-The three-carbon carbohydrate directly produced by the Calvin cycle and used to build glucose

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light-dependent reactions

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-The biochemical pathway that converts radiant energy (sunlight) into chemical energy in the form of ATP and NADPH
-Relies on the work of pigments and electron transport chains for energy transfer

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NADPH

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-The energy shuttle generated by the light-dependent reactions and used by the Calvin cycle to help produce glucose

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noncyclic electron flow

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-The movement of electrons during the light-dependent reactions that utilizes both photosystems and produces ATP, NADPH, and oxygen
-Electrons move from water to NADP+

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photophosphorylation

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-The chemiosmotic process by which ATP is generated as an H+ ion diffuses across the thylakoid membrane via ATP synthase
-Relies on the energy generated by the proton gradient

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photorespiration

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-A metabolic pathway employed on dry, hot days when stomata close and leaf concentrations of O₂exceed CO₂
-Uses O₂and generates CO₂but no additional ATP, effectively decreasing photosynthetic productivity

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photosynthesis

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-The biochemical pathway utilized by photoautotrophs to produce carbohydrate monomers from carbon dioxide and water
-Represented by the sum equation 6CO₂+ 6H₂O + sunlight energy → C6H12O6 (subscripted) + 6H₂O

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photosystem

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-A collection of pigments in the thylakoid membrane of the chloroplast that absorbs light
-Contains many light harvesting complexes that surround and direct light toward the reaction center

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photosystem I

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-One of two collections of pigments embedded in the thylakoid membrane of the chloroplast
-Contains P700 chlorophyll a at its reaction center
-Directly connected via electron transport chains to photosystem II and to the production of NADPH

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photosystem II

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-One of two collections of pigments embedded in the thylakoid membrane of the chloroplast
-Contains P680 chlorophyll a at its reaction center
-Accepts electrons from the splitting of water and directs them down an electron transport chain toward photosystem I

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primary electron acceptor

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-The first electron acceptor of the electron transport chain that starts a series of redox reactions

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reaction center

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-The area in the photosystem concentrated with chlorophyll a toward which all of the absorbed energy from light is directed from the accessory pigments

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rubisco (ribulose carboxylase)

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-The enzyme that catalyzes the reaction between CO₂and RuBP to start the Calvin cycle
-Incorporates inorganic CO₂into an organic molecule, "fixing" the carbon

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RuBP (ribulose biphosphate)

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-The five-carbon compound used to incorporate CO₂into an organic compound in the first step of the Calvin cycle
-Regenerated in the last step of the Calvin cycle

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stroma

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-The space inside the inner membrane of the chloroplast surrounding the grana
-The site of the light-independent reactions (Calvin cycle) of photosynthesis

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thylakoid

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-The disc-shaped folds of the inner membrane of a chloroplast arranged in stacks called grana
-The site of the light-dependent reactions of photosynthesis
-Serves to increase the surface area of the inner membrane of the chloroplast for increased efficiency of light absorption and, thus, photosynthesis

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visible light

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-The region on the electromagnetic spectrum where wavelengths range from 380nm (violet light) to 750nm (red light)
-All wavelengths in this region are detected as discrete colors by the human eye

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wavelength

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-The distance from one peak of a wave to the next
-Inversely proportional to the frequency of the wave