Chapter 10 - Photosynthesis Flashcards
photosynthesis
The conversion of light energy to chemical energy that is stored in sugar or other organic compounds; occurs in plants, algae, and certain prokaryotes.
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 molecules from inorganic ones.
heterotroph
An organism that obtains organic food molecules by eating other organisms or substances derived from them.
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.
stoma
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.
thylakoid
A flattened, membranous sac inside a chloroplast. Thylakoids often exists in stacks called grana that are interconnected; their membranes contain molecular “machinery” used to convert light energy to chemical energy.
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.
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 membranes of certain prokaryotes, convert solar energy to the chemical energy of ATP and NADPH, releasing oxygen in the process.
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.
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 and phosphate by means of chemiosmosis, using a proton-motive force generated across the thylakoid membrane of the chloroplast or the membrane of certain prokaryotes during the light reactions of photosynthesis.
carbon fixation
The initial incorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic prokaryote).
wavelength
The 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
That portion of the electromagnetic spectrum that can be detected as various colors by the human eye, ranging in wavelength from about 380 nm to about 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 and 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
action spectrum
A graph that profiles the relative effectiveness of different wavelengths of radiation in driving a particular process.
chlorophyll b
An accessory photosynthetic pigment that transfers energy to chlorophyll a.
carotenoids
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.
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.
