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Energy Metabolism: Photosynthesis (Photosynthesis (Light-Dependent…

- - - - atom doesn't carry as many electrons as it could
      - compounds in oxidized forms:
        
        carbon as carbon dioxide (CO2)
        
        sulfur as sulfate (SO2-)
        
        nitrogen as nitrate (NO3-)
        
        oxidized compounds often contain > O2
      - oxidation reaction increases + charge
    - - represents # of electrons lost
    - - electrons are added to an atom
      - reduction reaction
        
        reduces the + charge on an atom
      - reduced compounds contain H
      - most compounds are in the reduced state
    - - ability to force electrons onto compounds
      - important in plants
    - - NAD+
      - NADP+
      - take electrons away from other molecules
    - - NADH
      - NADPH
      - they place electrons onto other molecules
    - - the tendency to accept or donate electrons varies
  - - - transport electrons over short distances w/in membrane
      - pick up 2 electrons
        
        then bind 2 protons
      - hydrophobic
    - - small protein
      - carries electrons on a metal atom
        
        copper
      - loosely associated w/ chloroplast membrane
    - - small proteins
      - contain heme, which holds an iron atom
      - important in chloroplasts thylakoid membrane
      - can't be removed w/out destroying membrane
  - - - oxidative phosphorylation
        
        ADP phosphorylated to ATP
        
        occurs in all parts of the plant at all times
      - substrate-level phosphorylation
        
        phosphate is forced onto ADP
        
        occurs in all parts of the plant at all times
      - photophosphorylation
        
        involved light energy in photosynthesis
        
        only occurs in chloroplasts in light
- - - - conversion of CO2 to carbohydrate
      - RuBP (acceptor molecule)
        
        not ideal
    - - electrons & energy added in next 2 steps
  - - - constructive metabolism (rearranging & altering molecules)
      - anabolic reactions
      - 2 most important: synthetic pathways of polysaccharides and fats
      - short term storage: ATP & NADPH
      - intermediate storage: glucose & sucrose
      - long term storage: starch & lipids
  - - - infrared light
      - microwaves
        
        so little energy per quantum
        
        makes pigment of molecule warmer
      - ultraviolet light
      - radio waves
      - X-rays
      - gamma rays
      - visible light
    - - doesn't use high-energy quanta
    - - release of light by a pigment
    - - shows which wavelengths are most strongly absorbed by a pigment
    - - shows which wavelengths are most effective at powering a photochemical process
    - - P700
        
        The pair of chlorophylls name because they absorb red light at 700nm
      - works with Photosystem II
      - transfers electrons from H2O to NADPH
      - happens after Photosystem II after electrons pass through the ETC
        
        electrons are then boosted again by light
        
        pass through a second ETC to NADP+
        
        reducing it to NADPH
    - - works with photosystem I
      - Electrons are passed from water to P680
        
        then their energy is boosted by light
        
        then move through the ETC
        
        this last step is what produces ATP
    - - chemiosmotic phosphorylation
        
        light is involved
        
        it is photophosphorylation
      - grana
        
        set of thylakoids
        
        frets are thylakoids that lie between grana
      - stroma
        
        liquid surrounding the thylakoid system
      - thylakoid lumen
        
        enzymes and electron carriers of the photosystems are embedded in the membrane layer
        
        ATP Synthase
        
        synthesize ATP from ADP and phosphate
        
        noncyclic electron transport
        
        when electrons flow smoothly from water to NADPH
  - - - endergonic reactions driven by ATP :star:
      - requires new bonding orbitals
        
        electrons are carried here by NADPH
- - - - Photosynthesis (direct)
      - Respiration of organic compounds (indirectly)
  - - - used to assimilate small inorganic molecules
    - - all cyanobacteria
      - few bacteria capable of photosynthesis
      - all green plants
  - - - Obtains energy from this
    - - all fungi
      - all completely parasitic plants : :
      - nonphotosynthetic prokaryotes
      - All animals
  - - - Example: young white seedlings
        
        white & heterotrophic while germinating underground
        
        become photoautotrophic after emerging into sunlight
- - - - water is conserved by stomata closing
  - - - transported through
        
        concentrated in a leaf
        
        where then oxygen is kept away from RuBP carboxylase
    - - has a very high affinity for CO2
  - - - palisade parenchyma above & spongy mesophyll below
      - this structure is excellent at absorbing CO2
      - inefficient for conserving water
    - - leaf cells frequently pack together w/ no intracellular space
      - water loss is reduced
      - this slows photosynthesis
  - - - cactus family
      - many orchids
      - bromeliads
      - lilies
      - euphorbias
  - - - color or wavelengths it contains
    - - contains entire visible spectrum
      - noon is prime time for efficient photosynthesis
        
        for plants in deserts, grasslands, and the top layer
    - - light intensity or brightness
      - more light is available on a clear day not cloudy
    - - appears that to the left no photosynthesis occurs
    - - number of hours per day sunlight is available