Photosynthesis Flashcards
(18 cards)
Autotrophs
Organisms capable of producing all of their required molecules
Photosynthesis
Light - dependent oxygenic CO2 fixation
Requires light, produces O2, converts CO2 into organic molecules
Reductive process
Light Reactions
Converts light energy into the CPE if ATP and NADPH
Enzymatic Reactions
Use ATP/NADPH to produce carbohydrate
Products of photosynthesis
1) Sucrose: highly water soluble, mobile
2) Starch: insoluble starch grains, storage
Electrons
Provided by water (must be split)
These electrons are low energy
Mesophyll Cell
Photosynthetic cells
Contain dozens of chloroplasts
Chloroplasts
Double membrane
One membrane has porins, the other does not
Stroma: Site of Calvin cycle
Light
Plant absorb visible light
Green = cells don’t absorb green light very well
Photosynthetic Pigments
Chlorophylls and carotenoids
Chla and Chlab
Carotenoids cant absorb orange colour
An electron in Chl receives the energy of a photon - Chl* (excited state)
Electron is moved to a higher energy orbital
The energy will transfer along a series of pigments, until ending at a RChl
Pigments packed tight together in thylakoids
Reaction center chlorophyll (RChl)
3 possible states: ground sate (RChl), excited state (RChl*), and oxidized state (RChl+)
HEE is taken from RChl, and replaced with a low energy electron
P680
Photosystem II (PSII)
Photon enter, excites electron
Energy is transferred to RChl (P680)
Receives LEE from water splitting reaction
HEE is then transferred along PSII reaction center complex
HEE is released into thylakoid to pump H+ concentration gradient
Photosystem I (PSI)
Electron, now has low energy, enters from thylakoid
Photon re-excites electron
HEE leaves into stroma on Fd (electron carrier)
RChl is P700
No OEC, electron comes from PSII
Electron carriers
Fd (ferredoxin) - carries 1 electron
FdO -> FdR
NADPH - carries 2 electrons
ATP synthase
ATP is regenerated by bringing H+ down concentration gradient
H+ concentration gradient is created from HEE from PSII and water splitting reaction
Calvin Cycle
Enzyme: Rubisco (RuBP)
Converts CO2 into 3C sugars, using ATP and NAHPH
3C sugars converted in starch or sucrose (although not a part of Calvin cycle)
Starch
Insoluble
Temporary storage molecule
Located in stroma, but also roots and underground storage organs
Sucrose
Water soluble
Energy transport molecule
Moved from leaves during the day to rest of plant
Starch is converted into sucrose at night to be exported
