Chapter 7.txt

  1. absorption spectrum
    Range of wavelengths that a given type of pigment can absorb.
  2. accessory pigment
    A pigment that absorbs and transfers light energy to a photosystem; extends the range of light wavelengths for photosynthesis; e.g., a carotenoid.
  3. anthocyanin
    One of a class of accessory pigments that reflect red to blue light.
  4. ATP synthases
    A type of membrane-bound active transport protein that also catalyzes the formation of ATP.
  5. autotrophs
    [Gk. auto, self, and trophos, feeder] An organism that synthesizes its own food from simple inorganic compounds in its environment with energy captured from the sun or from oxidizing inorganic substances; e.g., a photoautotroph or chemoautotroph.
  6. C3 plants
    Type of plant in which threecarbon PGA is the first stable intermediate to form after carbon fixation.
  7. C4 plants
    Type of plant in which four-carbon oxaloacetate is the first stable intermediate to form after initial carbon fixation; in these plants, carbon is fixed twice, in two different types of photosynthetic cells.
  8. Calvin-Benson cycle
    Cyclic reactions that form sugar and regenerate RuBP in the second stage of photosynthesis. The reactions require carbon (from carbon dioxide). They use energy from ATP and hydrogens and electrons from NADPH, both of which form in the first stage.
  9. CAM plants
    Type of plant that conserves water by opening stomata only at night, when it fixes carbon by repeated turns of the C4 pathway; stands for crassulacean acid metabolism.
  10. carbon fixation
    Process by which any autotrophic cell incorporates carbon atoms into a stable organic compound. Different cells get carbon dioxide from the air or dissolved in water.
  11. carotenoids
    One of a class of accessory pigments in photosynthesis that reflect red, orange, and yellow light. One kind, beta-carotene, is a precursor of vitamin A.
  12. chlorophyll a
    [Gk. chloros, green, + phyllon, leaf] In plants and algae, a pigment that is a receptor for the photon energy required to start photosynthesis; it absorbs mainly violet and red light and reflects or transmits green light.
  13. chlorophyll b
    An accessory pigment that absorbs mainly blue and orange light.
  14. chloroplasts
    Organelle of photosynthesis in plants and algae. Two outer membranes enclose a semifluid interior, the stroma. A third membrane forms a compartment inside that functions in ATP and NADPH formation; sugars form in the stroma.
  15. cuticle
    Of plants, a cover of transparent waxes and cutin on the outer wall of epidermal cells. Of annelids, a thin, flexible coat. Of arthropods, a lightweight exoskeleton hardened with chitin.
  16. cyclic pathway
    Oldest photosynthetic pathway. Photon energy forces electrons out of membrane-bound photosystems to transfer systems, which return them to the photosystems. Electron flow across the membrane sets up H+ gradients that drive ATP formation.
  17. electromagnetic spectrum
    All wavelengths of photon energy from gamma rays less than 10�5 nanometers long to radio waves more than 10 kilometers long.
  18. electron transfer chains
    Array of enzymes and other molecules in a cell membrane that accept and give up electrons in sequence; operation of chain releases the energy of the electrons in small, usable increments.
  19. heterotrophs
    [Gk. heteros, other, + trophos, feeder] Organism that cannot make its own food; feeds on other organisms, their wastes, or their remains.
  20. light-dependent reactions
    First stage of photosynthesis. Pigments trap photon energy, which is transduced to ATP chemical energy. In a noncyclic pathway, a reduced coenzyme, NADPH, also forms.
  21. light-independent reactions
    Second stage of photosynthesis. Involves carbon fixation and cyclic reactions that form sugars and regenerate an organic compound that is the cycle�s entry point. ATP from the first stage delivers energy that drives the reactions. NADPH from the first stage donates electrons and hydrogen building blocks. The carbon and nitrogen come from CO2.
  22. noncyclic pathway
    [L. non, not, + Gk. kylos, circle] The light-dependent reactions of photosynthesis that produce both ATP and NADPH; its oxygen by-product is the basis of Earth�s oxygen-rich atmosphere.
  23. PGA
    Phosphoglycerate. During glycolysis, the intermediate that results after ATP has formed by substrate-level phosphorylation; also the first stable intermediate of the Calvin�Benson cycle of photosynthesis.
  24. PGAL
    Phosphoglyceraldehyde. During glycolysis, the intermediate that gives up electrons and hydrogen to form NADH. During turns of the Calvin�Benson cycle, two PGALs form one sugar; rearrangements of ten others regenerate a compound that is the entry point for the cycle.
  25. photolysis
    [Gk. photos, light, + -lysis, breaking apart] Reactions that split water molecules, which release electrons for the noncyclic pathway of photosynthesis; oxygen is a by-product.
  26. photons
    Unit of electromagnetic energy; has wave-like and particle-like properties.
  27. photosynthesis
    The process by which photoautotrophs capture sunlight energy and use it in the formation of ATP and NADPH, then in the formation of sugars from carbon dioxide and water. ATP gives up energy that drives the sugar-building reactions, and NADPH donates electrons and hydrogen building blocks.
  28. photosystems
    In photosynthetic cells, a cluster of membrane-bound pigments and other molecules; it converts light energy to chemical energy.
  29. phycobilins
    One of a class of accessory pigments in cyanobacteria and red algae that reflects red to blue light.
  30. pigments
    Any light-absorbing molecule.
  31. reaction center
    At a photosystem�s center, a special pair of chlorophyll a molecules; the center loses electrons on absorption of photon energy, thereby initiating the lightdependent reactions of photosynthesis.
  32. rubisco
    RuBP carboxylase. Carbon-fixing enzyme of the C3 photosynthesis pathway.
  33. RuBP
    Ribulose bisphosphate. A five-carbon organic compound; the entry point for the Calvin�Benson cycle, which regenerates it.
  34. stomata
    A gap between two plumped guard cells that lets water vapor and gases diffuse across the epidermis of a leaf or primary stem; diffusion stops when the cells lose water and collapse.
  35. stroma
    The semifluid matrix between the thylakoid membrane system and two outer membranes of a chloroplast where sucrose, starch, cellulose, and other end products of photosynthesis are built.
  36. thylakoid membrane
    A chloroplast�s inner membrane system, often folded as flattened sacs, that forms a continuous compartment in the stroma. In the first stage of photosynthesis, pigments and enzymes in the membrane function in the formation of ATP and NADPH.
  37. wavelength
    The distance between the crests of two successive wavelike forms of energy in motion.
  38. xanthophylls
    One of a class of accessory pigments in photosynthesis that reflects yellow to orange light.
Card Set
Chapter 7.txt
Chapter 7