Photosynthesis
Hill Reagents
These are substances that accept electrons transferred from water by the photosynthetic light reactions and thus lead to evolution of oxygen up illumination.
The Hill reagent is NADP+, but some other chemicals can substitute for it in vitro
DCPIP - when this is added it can strip chloroplasts without NADP+, the reagent was decolourised and the chloroplasts began to produce oxygen even in the absence of carbon dioxide.
Calvin cycle
Has branches
Put in 18 Carbons as 6C3 which is rearranged to get 2C5
Ribulose biphosphate carboxylase/ oxygenase: The most abundant protein on earth + Slowest enzyme that we know of. Half of the nitrogen in our body comes from Nitrogen in Haber bosch process
16 sub unit protein composed of 8 large sub units coded by chloroplast DNA and 8 small sub units coded by Nuclear DNA
Physiological limits on photosynthesis
CO2 is absorbed by moist surfaces of the spongy parenchyma cells. Moist surfaces which gas dissolves into - loss a lot of water through evaporation in the process of CO2 absorption (Need a lot of water).
Plants have pores in the bottoms of their leaves to prevent water loss, this has an effect of CO2 absorption and O2 release
Water evaporation goes up exponentially as the heat rises = substantial problem global warming and crop growth
Light dependant reactions
Electrons go to reducing NADP (used in catabolism) to NADPH - is (used in anabolism)
Consequence of proton gradient is to generate ATP
As protons pass across the gradient the C10 cylinder rotates, as they do so they generate ATP
Chloroplast F0 domains have up to 15C sub units. F0 moves things around one click - allowing about 14 protons, giving 3 ATP
Phototroph can get energy but cant make 'stuff'
Light energy is absorbed by chlorophylls a and b
Once a photon hits the antenna it is transferred very rapidly to a reaction centre.
Light absorbed by chlorophyll is released rapidly as heat and fluorescence.
Antenna pigments are arranged in order light harvesting complexes LHC's, with pigments orientated so that energy of an exciton can easily be transferred to an adjacent pigment molecule etc. until it reaches a reaction centre
Reaction centre
the pair of chlorophyll a molecules are converted to a high energy state. As a result the redox potentials of the activated pigments are reduced. ( Kicks an electron from a low energy state to a high energy state)
NADPH is only useful as it is a strong reducing agent
Photosystem 2 comes first
photosystem 1 comes sescond
Redox carriers
Quinol reduced on one side of the membrane then oxidised- picks up proton as this happens and creates a proton gradient.
Photosystem 1 Uses iron sulfur proteins as its electron carriers instead of quinol
Electrons come from photosystem 1
these are carried to Photosystem 2, where they are converted to energy
cynobacteria get electrons from water
Oxygen is a waste product of photosynthesis. Iron Formation is product of increased oxygen in the atmosphere
Strip electrons away from water to make oxygen = complex of 4 manganese ions to produce that
Before this we had a reducing atmosphere
Now we have an oxidising atmosphere
It is estimated that PS increased global production of reduced carbon by 4500-45000 times