photosynthesis Flashcards
why is the upper epidermis transparent
allows more light to be absorbed by chloroplast
why are palaside mesophyll cells verticle
to increase photosynthesis
how are leave arrangements made to maximise photosynthesis
minimal overlapping so no shade
how do stoma maximise photosynthesis
open and close in responce to changes in light intensity
why do leaves have a large surface area
collects as much solar energy as possible
why are their aire spaces in the lower mesophyll
to allow diffusion and storage of co2 and o2
structure of the chloroplast
outer membrane
stroma
thylakoid
thylakoid membrane
inner membrane
describe the light dependant reaction
occures between the stroma and the inner thylakoid
photosystem captures solar energy
accessory pigments vibrate when light hits them
it forces energy down to chlorophyll A in the reaction centre
when enough energy is absorbed 2 electrons explode of magnesium
magnesium gets more electrons by photolysis in the reaction centre
what is photolysis
H2O -> 2H+ + 2e- + 1/2 O2
where does the oxygen go after photolysis
diffuses to atmosphere or mitchrocondria for respiration
what is the reaction centre
at the bottom of the photosystem
with primary pigment chlorophyll A
Mg+ and hydrophobic tail
where does the light independant reaction occur
in the stroma
describe how ATP is produced
electrons bounce from one cytochrome to another loosing strength, this is called the electron transport chain
electrons move into the reaction centre of PS1
the electrons helpt to pump protons into the thylakoid by active transport
H+ ions move by facilitated diffusion through ATP synthase down the electrochemical gradient
chemiosmosis occurs to produce ATP
excited electrons are released and react with H+ ions to reduce NADP
what is proton motive force
desire of protons to leave the thylakoid because of the force of their possitive charge
describe the light independant reaction
CO2 is added to the reaction and binds to RuBP which has 5 carbons by the enzyme rubisco
this produces 2 molecules of 3 carbon GP
reduced NADP becomes NADP and the H+ is used to make TP. this is catalysed by the bendohydrogenase enzyme
ATP is broken down
some of the TP leaves as glucose
what does RuBP mean
ribulose bisphosphate
what does GP mean
glycerate phosphate
what does TP mean
triose phosphate
what is the limiting factor
factor limiting the rate of photosynthisis
what is the compensation point
when there is no net exchange of gases in or out of the plant
why is light intensity a limiting reactant
because it is too low for the light dependant reaction
this means the level of ATP and Red NADP will also be low so the light independant reaction will also be running slowly
why is carbon dioxide a limiting factor
because at high light intensity the light dependant reaction is running very fast so lots of ATP and reduced NADP are made
but if their isnt enough CO2 it limits rate of reaction
why is temperature a limiting factor
because the enzyme ribsico in the light independant reaction wont be running fast enough if temperature is low, decreasing rate of photosynthesis
why might water be considered a limiting fator
because low water levels causes stomata to close
but then CO2 cant get in
so CO2 becomes the limiting factor
what happens to the clavin cyle in low light intensity
GP conc increases because less ATP and RED NADP is available to convert it to TP
TP conc decreases
RUBP conc decreases
what happens in the calvin cycle in low CO2 conc
GP conc decreases because less RUBP combines with CO2
less TP conc
RUBP conc increaes because less of it reacts with CO2
