43 terms

Photosynthesis (Vocabulary)

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autotroph
organism that can capture energy from sunlight or chemicals and use it to produce its own food from inorganic compounds; also called a producer
heterotroph
an organism that obtains organic food molecules by eating other organisms or their byproducts and that cannot synthesize organic compounds from inorganic materials
photosynthesis
process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches
chlorophyll
a green pigment found in the chloroplasts of plants, algae, and some bacteria
mesophyll
specialized ground tissue that makes up the bulk of most leaves; performs most of a plant's photosynthesis
stomata
the small openings on the undersides of most leaves through which oxygen and carbon dioxide can move
light reactions
the steps in photosynthesis that occur on the thylakoid membranes of the chloroplast and that convert solar energy to the chemical energy of ATP and NADPH, evolving oxygen in the process.
Calvin Cycle
the second of two major stages in photosynthesis (following the light reactions), involving atmospheric CO2 fixation and reduction of the fixed carbon into carbohydrate.
NADP+
nicotinamide adenine dinucleotide phosphate, an acceptor that temporarily stores energized electrons produced during the light reactions.
phosphorylation
the process of adding a phosphate group to ADP to make ATP; cells use the energy released by ATP to power essential activities
carbon fixation
the incorporation of carbon from carbon dioxide into an organic compound by an autotrophic organism.
wavelength
the distance between crests of waves, such as those of the electromagnetic spectrum.
electromagnetic spectrum
the entire frequency range of electromagnetic waves
visible light
that portion of the electromagnetic spectrum detected as various colors by the human eye, ranging in wavelength from about 380 nm to about 750 nm.
photons
a quantum, or discrete amount, of light energy.
spectrometer
instrument that measures index of light reflection
absorption spectrum
the range of a pigment's ability to absorb various wavelengths of light.
chlorophyll a
a blue-black plant pigment having a blue-green alcohol solution
chlorophyll b
a dark-green plant pigment having a brilliant green alcohol solution
carotenoid
yellow and orange plant pigments that aid in photosynthesis
photosystems
light-collecting units of the chloroplast
reaction center
complex of proteins associated with two special chlorophyll a molecules and a primary electron acceptor. Located centrally in a photosystem, this complex triggers the light reactions of photosynthesis. Excited by light energy, one of the chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an electron transport chain.
primary electron acceptor
a specialized molecule sharing the reaction center with the pair of reaction-center chlorophyll a molecules; it accepts an electron from one of these two chlorophylls.
photosystem I
one of two light-harvesting units of a chloroplast's thylakoid membrane; it uses the P700 reaction-center chlorophyll.
photosystem II
one of two light-harvesting units of a chloroplast's thylakoid membrane; it uses the P680 reaction-center chlorophyll.
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+.
noncyclic phosphorylation
the production of ATP by noncyclic electron flow.
cyclic electron flow
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.
cyclic phosphorylation
the generation of ATP by cyclic electron flow
glyceraldehyde-3-phosphate
G3P, a three carbon sugar produced directly from the Calvin cycle
rubisco
enzyme that catalyzes the first step of the Calvin cycle
C3 plant
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.
C4 plant
a plant that prefaces the Calvin cycle with reactions that incorporate CO2 into a four-carbon compound, the end product of which supplies CO2 for the Calvin cycle.
CAM plant
plant that carries out crassulacean acid metabolism; carbon is initially fixed into organic acids at night in the reaction of CO2 and phosphoenolpyruvate, catalyzed by PEP carboxylase; during the day the acids break down to yield CO2, which enters the Calvin cycle.
photorespiration
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.
bundle-sheath cells
a type of photosynthetic cells arranged into tightly packed sheaths around the veins of a leaf
PEP carboxylase
an enzyme that adds carbon dioxide to phosphoenolpyruvate (PEP) to form oxaloacetate.
CAM
crassulacean acid metabolism; a biochemical pathway in certain plants in which CO2 is incorporated into organic acids at night and released for fixation in the Calvin cycle during the day
plastoquinone
the primary electron acceptor for electrons leaving photosystem II.
cytochrome complex
electron carrier in photosystem II
plastocyanin
acts as an electron carrier between the cytochrome b6f and photosystem I (PSI) complexes in the photosynthetic electron-transfer chain.
ferredoxin
receives electrons from photosystem I and passes them to NADP reductase
NADP reductase
transfers electrons to NADP to form NADPH