unit 3. b - bio

• Photosynthesis


  The process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar

  
• Electromagnetic spectrum

  The range of all types of electromagnetic radiation
• How light is absorbed

  Visible light = white light

  
• Chlorophyll


  • Green pigment that gives leaves their color and resides in the thylakoid membranes of the chloroplast
  • Stimulates photosynthesis with red and blue light

  
• Sites of photosynthesis

  • Mesophyll: tissue in the interior of the leaf, where chloroplasts are found
  • Stomata: pores in which CO2 enters and oxygen exits the leaf

  
• Chloroplast

  • Where photosynthesis takes place
  • Stroma: dense fluid
  • Thylakoids
  • Grana

  
• Organisms that perform photosynthesis

  • Autotrophs: self-feeders, producers, organisms that can make their own food
  • Plants
  • Plankton
  • Algae
  • Kelp
  • Cyanobacteria

  
• Glucose

  Can be broken apart for energy to power reactions
• Polysaccharides

  • Cellulose: structural component of cell walls
  • Starch: Long-term energy stored that the plant can use later
• Stages of photosynthesis

  • Light-dependent reaction
  • Calvin Cycle (light-independent or dark reaction)

  
• Light-dependent reactions

  • Photosystem: composed of a reaction-center complex surrounded by several light-harvesting complexes
  • Light-harvesting complex: consists of various pigment molecules (chlorophyll a, chlorophyll b, carotenoids)
  • Chlorophyll a (reaction-center complex)
  • Primary electron acceptor

  
• Light-dependent reactions

  Photon -> pigment molecules (light-harvesting complex) -> Chlorophyll a (reaction-center complex) -> Primary electron acceptor -> First step: transfer of electrons from chlorophyll a to the primary electron acceptor
• Linear energy flow

  1. Plastoquinone = Pq

  2. Plastocyanin = Pc

  3. Ferredoxin = Fd
• Cyclic electron flow

  • No NADPH produced
  • No oxygen release
  • Generates ATP
• Chemiosmosis


  The process by which ATP is generated in the mitochondria and chloroplasts of cells
• Calvin Cycle

  1. Only 1 is a net gain (used by the plant cell)

  2. 5 molecules are recycled to regenerate 3 molecules of RuBP
• Alternative mechanisms of carbon fixation

  • Transpiration: evaporative loss of water from leaves
  • C4 plants: Preface Calvin cycle with an alternative mode of carbon fixation that forms a four-carbon compound as its first product
  • CAM plants: Open stomata at night, close them during the day
• Leaf anatomy of C4 plants

  • Phosphoenolpyruvate (PEP): 3-carbon compound present in mesophyll cells, acts as a primary carbon dioxide acceptor, converted into OAA by the action of PEP carboxylase