Photosynthesis: Vocab Only

• photosynthesis


  conversion of light energy to chemical energy that's stored in sugars or other organic compounds; occurs in plants, algae, & certain prokaryotes
• autotroph


  an organism that obtains organic food molecules w/o eating other organisms or substances derived from other organisms (producer)
• heterotroph


  an organism that obtains organic food molecules by eating other organisms or substances derived from them (consumer)
• chlorophyll


  green pigment located w/i the chloroplasts of plants & algae & in the membranes of certain prokaryotes
• mesophyll


  ground tissue of a leaf, sandwiched between the upper & lower epidermis & specialized for photosynthesis
• stoma


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


  dense fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from CO2 & water
• thylakoid


  a flattened membraneous sac inside a chloroplast
• light reactions


  the first of two major stages in photosynthesis; these reactions occur in the thylakoid membranes of the chloroplast & convert solar energy to chemical energy of ATP & NADPH, releasing oxygen in the process
• Calvin cycle


  the second of two major stages in photosynthesis, involving fixation of atmospheric CO2 & reduction of the fixed carbon into carbohydrate
• NADP+


  nicotinamide adenine dinucleotide phosphate, an electron acceptor that, as NADPH, temporarily stores energized electrons produced during the light reactions
• photophosphorylation


  the process of generating ATP from ADP & phosphate by means of a proton-motive force generated across the thylakoid membrane of the chloroplast during the light reactions of photosynthesis
• carbon fixation


  initial incorporation of carbon from CO2 into an organic compound by an autotrophic organism
• wavelength


  distance between crests of waves, such as those of the electromagnetic spectrum
• electromagnetic spectrum


  the entire spectrum of electromagnetic radiation ranging in wavelength from less than a nanometer to more than a kilometer
• visible light


  portion of the electromagnetic spectrum that can be detected as various colors by the human eye, ranging in wavelength from 380 nm to 750 nm
• photon


  a quantum, or discrete quantity, of light energy that behaves as if it were a particle
• spectrophotometer


  an instrument that measures the proportions of light of different wavelengths absorbed & transmitted by a pigment solution
• absorption spectrum


  the range of a pigment's ability to absorb various wavelengths of light; also a graph of such a range
• chlorophyll a


  a photosynthetic pigment that participates directly in the light reactions, which convert solar energy to chemical energy
• carotenoids


  an accessory pigment, either yellow or orange, in the chloroplasts of plants that increase the spectrum of light that can be absorbed
• photosystem


  a light-capturing unit located in the thylakoid membrane of the chloroplast, consisting of a reaction-center complex surrounded by numerous light-harvesting complexes
• reaction-center complex


  a complex of proteins associated w/ a special pair of chlorophyll a molecules & a primary electron acceptor
• light-harvesting complex


  a complex of proteins associated w/ pigment molecules that captures light energy & transfers it to reaction-center pigments in a photosystem
• primary electron acceptor


  in the thylakoid membrane of a chloroplast, a specialized molecule that shares the reaction-center complex w/ a pair of chlorophyll a molecules & that accepts an electron from them
• photosystem 2


  a light-capturing unit in the thylakoid membrane; it has 2 molecules of P680 chlorophyll a @ its reaction center
• photosystem 1


  found in the thylakoid membrane; it has 2 molecules of P700 chlorophyll a @ its reaction center
• linear electron flow


  a route of electron flow during the light reactions of photosynthesis that involves both photosystems & generates ATP, NADPH, & O2
• cyclic electron flow


  a route of electron flow during the light reactions of photosynthesis that involves only photosystem 1 & that produces ATP but NOT NADPH or O2
• G3P


  a 3-carbon carbohydrate that's the direct product of the Calvin cycle
• rubisco


  enzyme that catalyzes the first step of the Calvin cycle
• C3 plant


  plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a 3-carbon compound as the 1st stable intermediate (ex: rice, wheat, soybeans)
• photorespiration


  a metabolic pathway that consumes oxygen & ATP, releases carbon dioxide, & decreases photosynthetic output
• C4 plant


  plant in which the Calvin cycle is preceded by reactions that incorporate CO2 into a 4-carbon compound, the end product of which supplies CO2 for the Calvin cycle
• bundle-sheath cells


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


  a type of loosely arranged photosynthetic cell located between the bundle sheath & the leaf surface
• Crassulacean acid metabolism (CAM)


  an adaptation for photosynthesis in arid conditions

  • at night, a plant takes up CO2 & incorporates it into a variety of organic acids which it stores until morning
  • during the day, CO2 is released from the organic acids for use in the Calvin cycle
• CAM plant


  plant that uses CAM, an adaptation for photosynthesis in arid conditions