Photosynthesis Flashcards
Photosynthesis
Energy for all life on Earth ultimately comes from sunlight captured by photosynthesis
One of most significant metabolic processes on Earth
Photosynthesis equation
6CO2 + 12H2O + light energy=C6H12O6 + 6H2O + 6O2
Oxygenic photosynthesis is carried out by
Cyanobacteria
7 groups of algae
All land plants (have chloroplasts)
Anoxygenic photosynthesis does not produce O2 and is carried out by:
At least 5 different groups of BacteriaAnoxygenic phototrophy is better term especially if energy gained from light is not used to fix CO2
Light-dependent” reactions where
Thylakoid membrane of the chloroplast
Light dependent reactions are called what
Photosynthetic electron-transfer reactions
“Light-independent” reactions.. were
stroma called carbon fixation
“Light-independent” reactions are called what
Carbon-fixation reactions in stroma
What do light DEPENDENT reactions do?
Capture energy from sunlight in Pigments
Use light energy to make ATP
reduce NADP+ to NADPH in thylakoid
Light Independent reactions do>
Use ATP and NADPH to power synthesis of organic molecules (monosaccharides) from CO2
in stroma
Where are pigments found
thylakoid membrane
2 types of pigments
Chlorophyll
Carotenoids (accessory)
Chlorophyll
a (main) and b (accessory)
Similar structure, different absorption spectra
Carotenoids (accessory)
Carotenes and xanthophylls
Example: b-carotene
Pigments
alternating single and double bonds (i.e., way to transfer electrons/energy)
2H2O oxidized =
produces O2 + 4H+ + 4e-
Chlorophyll loses electron
(oxidized);
chlorophyll gains electron
(reduced)
Photosystem organization
Light harvesting complex
Light harvesting complex
Capture photons (sunlight energy) Excitation energy (not e-!) transferred from one pigment to another until reaches reaction center
Reaction center
Contains chlorophyll special pair
Reaction center Contains
chlorophyll special pair
Chlorophyll special pair traps photon energy
passes excited electron to an acceptor
Electron donor restores electron to chlorophyll special pair
Donor = water
Oxidation of water = release of O2
4 steps of light dependent reaction
Primary photoevent & H2O oxidized
Charge separation
Electron transport
Chemiosmosis (ATP production)
First step of light dependent reaction photosystem II (comes before photosystem I)
Primary photoevent (Light energy (photons) absorbed) H2O oxidized (replenishes lost electrons to reaction center; releases O2)
second step of light dependent reaction
Charge separation (e- released to electron transport chain)
third step of light dependent reaction
photosystem I
Electron transport (e- reduce NADP+ to NADPH) H+ pumped from stroma into thylakoid space
fourth step in light dependent reaction
Chemiosmosis (ATP production)
H+ leave thylakoid space (via ATP synthase) to stroma
What steps occur in the thylakoid space
Steps 1-3
How are the electrons replaced in photosystem I
Produced in photosystem II that occurs before it
What produces ATP in the final step of light dependent reaction
ATP synthase using proton gradient
How are the electrons replaced in photosystem II
By oxidation of water the O2
