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Energy Metabolism: Photosynthesis (Nature of pigments (absorb certain…
Energy Metabolism: Photosynthesis
Energy Carriers
Photosynthesis
Energy enters the world
Converts light energy to chemical energy
e Pigments too big to move
too energized to control
Produces ATP
Photophosphorylation
ADP -> ATP
Oxidation Phosphorylation
Respire high energy compounds
Compounds force P on ADP
"Substrate level phosphorylation"
Environmental and Internal Factors
Light
Quality
Colors or Wavelengths
sunlight is pure white
blue light defected up
red light close to ground level
allows efficient photosynthesis
quantity
light intensity or brightness
poles light > than equator light
Under water
absorb blue and green light
appear different colors than land plants
Increases CO2 concentraions
Duration
Hours per day sunlight is avaliable
Equator has 12 hour days
Closer to the poles the shorter the day
Summer light
longer
brighter
Longer days
More photosynthesis
some chlorplasts fill up of starch
photosynthesis halts
Water
Availability affects photosynthesis
No water availability
Plant keeps stomata closed
C4 metabolism
Water lost for every CO2 absorbed
CO2 diffusion low
water loss high
CO2 is absorbed and kept
O is kept away
Crassulacean Acid metabolism
Improves conservation of H2O
Permits Photosynthesis
Stomata open at night when cool
Stomata closed during hot
ATP and NADPH not stable to last to night
CO2 stored on acids
CO2 cant escape at night
Stomata closed
Reducing powers
Oxidized
Atom can carry more electrons
CO2
electrons closer to O
C is +4 oxidative state
NAD+ and NADH oxidizing agents
Reduced compounds have H
Ability to force electron on compound
Important to plants
Redox potential
Ability to accept/donate e-
Photosynthesis
CO2 and H2O are cheap
Plants dont use energy
very stable
Reactants and products are nontoxic
Thylakoid reactions
H2O and light-> Atp and NDPH
Stroma Reactions
ATP + NADPH + CO2 -> Carbohydrate
Other Electron Carriers
Cytochromes
Small proteins that contain a cofactor
iron between +2 and +3
intrinsic membrane proteins
Carry proteins between close sites
Plastoquinones
Transport e- over short distances
Bind two protons
Hydrocarbon tail
Hydrophobic
dissolve easily
Plastocyanin
Small protein that carries electrons
metal atom
Bind two protons
does not travel far
The Nature of LIght
small fraction of spectrum
radiation
Particles called quanta
Also photons
Animals see 350-760nm
some insects see ultraviolet
Nature of pigments
materials that absorb color
some protect light sensitive substances
absorb certain quanta
Activates an electron
fluorescence
release of light
absorption spectrum
shows which wave lengths are absorbed
action spectrum
shows wavelengths that are most effective
reactions
Synthesis of ATP
ATP generated by light reaction
ATP synthetase
CF0-CF1 complex
Photophosphorylation
light used for ADP reaction to ATP
Chloroplasts
Stroma is thylakoids in one region
CF1 in portion that phosphorylates
ADP->ATP
Photosystem I
P700
Absorb red light
pair of chlorophylls
Ferrodoxin
located in thylakoid
small protein
active site containing 2Fe
Photosystem II
plastocyanin
Donates e- to Chlorophyll a
Recieves electrons form Q
Q is molecule of quinone
receives e- from phaeophytin
P680
electrons passed from H2O
energy boosted by light
energy used for electron transport chain
Leaf structure
Tropical plants
palisade parenchyma above
spongy mesophyll below
Excellent for absorbing CO2
inefficient H2O conservation
Reduced external surface
Cylindrical leaves
Minimizing water loss
CO2 Absorption is slow