[8] Vocabulary - Photosynthesis Flashcards
absorption spectrum
the range of a pigment’s ability to absorb various wavelengths of light; also a graph of such a range
action spectrum
a graph that profiles the relative effectiveness of different wavelengths of radiation in driving a particular process
autotroph
an organism that obtains organic food molecules without eating other organisms or substances derived from other organisms. Autotrophs use energy from the sun or from oxidation of inorganic substances to make organic molecule from inorganic ones.
C3 plants
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 plants
a plant in which the Calvin cycle is preceded by reactions that incorporate CO2 into a four-carbon compound, the end product of which supplies CO2 for the Calvin cycle
Calvin cycle
the second of two major stages in photosynthesis (following the light reactions), involving fixation of atmospheric CO2 and reduction of the fixed carbon into carbohydrate
CAM plants
a plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions. Im this process, carbon dioxide entering open stomata during the night is converted to organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed
carbon fixation
the initial incorporation of carbon from CO2 into an organic compound by an autotrophic organism
carotenoid
an accessory pigment, either yellow or orange, in the chloroplasts of plants and in some prokaryotes. By absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drive photosynthesis.
chlorophyll
a green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes. Chlorophyll A participates directly in the light reactions, which convert solar energy to chemical energy.
chlorophyll A
a photosynthetic pigment that participates directly in the light reactions, which convert solar energy to chemical energy
chlorophyll B
an accessory photosynthetic pigment that transfers energy to chlorophyll A
chloroplast
an organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water
crassulacean acid metabolism (CAM)
an adaptation for photosynthesis in arid conditions, first discovered in the family Crassulaceae. In this process, a plant takes up CO2 at night when stomata are open and incorporates it into a variety of organic acids; during the day, when stomata are closed, CO2 is released from the organic acids for use in the Calvin cycle
glyceraledehyde 3-phosphate (G3P)
a three-carbon carbohydrate that is the direct product of the Calvin cycle; it is also an intermediate in glycolysis
heterotroph
an organism that obtains organic food molecules by eating other organisms or substances derived from them
light reactions
the first of two major stages in photosynthesis (preceding the Calvin cycle). These reactions, which occur on the thylakoid membranes of the chloroplast or on the membranes of certain prokaryotes, convert solar energy to the chemical energy of ATP and NADPH, releasing oxygen in the process.
light-harvesting complex
a complex of proteins associated with pigment molecules (including chlorophyll A, chlorophyll B, and carotenoids) that captures light energy and transfers it to reaction-center pigments in a photosystem
linear electron flow
a route of electron flow during the light reactions of photosynthesis that involves both photosystems (I and II) and produces ATP, ANDPH, and O2. The net electron flow is from H20 to NADP+
mesophyll
Leaf cells specialized for photosynthesis. In C3 and CAM plants, mesophyll cells are located between the upper and lower epidermis; in C4 plants, they are located between the bundle-sheath cells and the epidermis
NADP+
the oxidized form of nicotinamide adenine dinucleotide phosphate, an electron carrier that can accept electrons, becoming NADPH. NADPH temporarily stores energized electrons produced during light reactions.
NADPH
the reduced form of nicotinamide adenine dinucleotide phosphate, which temporarily stores energized electrons produced during the light reactions. NADPH acts as “reducing power” that can be passed along to an electron accept, reducing it.
photon
a quantum, or discrete quantity, of light energy that behaves as if it were a particle
photophosphorylation
the process of generating ATP from ADP and phosphate by means of chemiosmosis, using a proton-motive force generated across the thylakoid membrane of the chloroplast or the membrane of certian prokaryotes during the light reactions of photosynthesis
photorespiration
a metabolic pathway that consumes oxygen and ATP, releases carbon dioxide, and decreases photosynthetic output. Photorespiration generally occurs on hot, dry, bright days, when the stomata close and the O2/CO2 ratio in the leaf increases, favoring the binding of O2 rather than CO2 by rubisco.
photosynthesis
the conversion of light energy to chemical energy that is stored in sugars or other organic compounds; occurs in plants, algae, and certain prokaryotes
photosystem
a light-capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes, consisting of a reaction-center complex surrounded by numerous light-harvesting complexes. There are two types of photosystems, I and II; they absorb light best at different wavelengths.
photosystem I
one of two light-capturing units in a chloroplast’s thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of P700 chlorophyll A at its reaction center
photosystem II
one of two light-capturing units in a chloroplast’s thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of P680 chlorophyll A at it’s reaction center
primary electron acceptor
In the thylakoid membrane of a the membrane of some prokaryotes, a specialized molecule that shares the reaction-center complex with a pair of chlorophyll a molecules and that accepts an electron from them.
reaction-center complex
a complex of proteins associated with a special pair of chlorophyll A molecules and a primary electron acceptor. Located centrally in a photosystem, this triggers the light reactions of photosynthesis. Excited by light energy, the pair of chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an electron transport chain.
reduction
the complete or partial addition of electrons to a substance involved in a redox reaction
rubisco
ribulose bisphosphate (RuBP) carboxylase-oxygenase, the enzyme that normally catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP). When excess O2 is present or CO2 levels are low, rubisco can bind oxygen, resulting in photorespiration
spectrophotometer
an instrument that measures the proportions of light of different wavelengths absorbed and transmitted by a pigment solution
stomata
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
stroma
the dense fluid within the chloroplast surrounding the thylakoid membrane and containing ribosomes and DNA; involved in the synthesis of organic molecules from carbon dioxide and water
electromagnetic spectrum
The entire spectrum of electromagnetic radiation, ranging in wavelength from less than a nanometer to more than a kilometer.
thylakoid
a flattened, membranous sac inside a chloroplast. Thylakoids often exist in stacks called grana that are interconnected; their membranes contain molecular machinery used to convert light energy to chemical energy.
visible light
the portion of the electromagnetic spectrum that can be detected as various colors by the human eye, ranging in wavelength from about 380nm to about 750nm
wavelength
the distance between crests of waves, such as those of the electromagnetic spectrum
