Photosynthesis Flashcards
what does life depend on
the continuous transfer of energy
in plants what is light energy absorbed by
the chlorophyll and then transferred into the chemical energy of the molecules formed during photosynthesis
site of photosynthesis
- the leaf in eukaryotic plants
- chloroplast are the cellular organelle where photosynthesis takes place
structure of the leaf
- large surface ares to absorb as much sunlight as possible
- arrangement on plants that minimises leaves overshadowing each other
- thin so short diffusion pathway
- transparent cuticle and epidermis that lets light through to the photosynthetic mesophyll cells
- land narrow upper mesophyll cells packed with chloroplast
numerous stomata for gas exchange
photosynthesis equation
6co2 + 6h20 = c6h12o6 + 6o2
3 stages of photosynthesis
- capturing light energy
- light dependent reaction
- light independent reaction
what captures light energy
chloroplast pigments (chlorophyll)
what happens during the light independent reaction (simple)
protons (hydrogen ions) are used to produce sugar
structure of chloroplast
- disc shaped
- 2- 10 um long
- 1 um in diameter
- surrounded by double membrane
role of chloroplast
- grana are stacks of up to 100 disc like structures called thylakoids where the light dependent stage of photosynthesis takes place
- within the thylakoids is chlorophyll
stroma
- fluid filled matrix where the light independent stage takes place
- has starch grains
photosynthesis involves the capture of light energy for
- add inorganic phosphate to ADP to make ATP
- split water into h + ions (protons) and OH - ions (photolysis)
what is oxidation
- a substance gains oxygen
- losses hydrogen
- loses electrons
- losses energy
what is reduction
- a substance loses oxygen
- gains hydrogen
- gains electron
gains energy
how is ATP made in photosynthesis
- when a chlorophyll molecule absorbs light energy it boosts the energy of a pair of electrons within the chlorophyll raising then to a higher energy state where they leave the chlorophyll molecule
- the chlorophyll molecule becomes ionised (photoionisation)
- the electron are taken up by the electron carrier
- chlorophyll is oxidised and electron carrier is reduced
- electrons are passed along electron carrier in oxidisation reduction reactions
- each new carrier is at a lower electron level than the previous one in the chain so energy is lost at each stage
- this energy is used to combine an inorganic phosphate with ADP to make ATP
what is the chemiosmotic theory
- each thylakoid is an enclosed chamber with protons (H +) are pumped from the stroma using protein carriers in the thylakoid membrane (protein pumps)
- energy is supplied by the water splitting by light
- the photolysis of water also produces protons which further increase their concentration inside the thylakoid space
- this creates and maintains a concentration gradient which a high concentration of protons inside the thylakoid space and a low concentration in the stroma
- the proteins cross the thylakoid membrane through ATP sythases channel proteins
- as the protons passes the protein channel they cause changes to the structure of the enzyme which catalyses the combination of ADP and Pi to form ATP
what is the process for the photolysis of water
- the replacements electrons for the chlorophyll molecules are provided from water molecules that are split using light energy
- these protons pass out of the thylakoid space through the ATP synthase channels and are taken up by NADP which becomes reduced NADPH
equation for the photolysis of water
2H2O –>4H+ + 4E- +O2
how is chlophyll structiually adapted to its function
- thylakoid membrane provides a large surface area for the attachment of chlorophyll, electrons carriers and enzymes
- granna has chlorophyll in a precise manner for maximum light absorption
- granal membranes have ATP synthase channels which catalyses the production of ATP
- chloroplast contains DNA and ribosomes so can manufacture some proteins involved in light dependent reactions
what is chlorophylls function
capture sunlight and carry out the light dependent reaction of photosynthesis
where does the light independent stage of photosynthesis take place
the stroma of the chloroplast
brief outline of the calvin cycle
RuBP + co2 = 2 GP + NADPh = 3 TP + ATP = RuBP
how is the chloroplast adapted to carry out the light independent reaction
- the fluid of the stoma contains all the enzymes needed to carry out the reaction
- stoma fluid surrounds the the grana and so the product of the light dependent reaction in the grana can readily diffuse into the stroma
- contains both dna and ribose so it can quickly manufacture some of the proteins involved
