chapter 10- photosynthesis Flashcards
what does photosynthesis do
convert solar energy into chemical energy
what is a thylakoid
structure inside the chloroplast
what is in the thylakoid membrane
photosynthetic enzymes and other molecules like pigments (chlorophyll)
where are chloroplasts found and in what quantity
found in mesophyll cells and there are 30-40 in each
what is the stroma
the fluid inside the chloroplasts
what are the characteristics/structures of thylakoids
thylakoids are stacked in structures called grana
the interior thylakoid membranes form interconnected sacs
chlorophyll is present in the membranes and makes them green
photosynthesis formula
6co2 + 12h2o + E -> c6h12o6 +6o2 +6h2o
water is fully oxidized to what
oxygen gas
co2 is reduced to what
oxygen in water
oxygen in sugar
carbon in sugar
light as behaves as discrete particles called
photons
what is an absorption spectrum
a pigment’s light absorption vs wavelength
what is chlorophyll a’s absorption spectrum related to photosynthesis
suggests that violet-blue and red wavelengths work better
what is an action spectrum
shows the effects of different wavelengths on a process
what is the main photosynthetic pigment
chlorophyll a
absorbs better
what do chlorophyll b and carotenoids do light-wise
chlorophyll b broadens spectrum used for photosynthesis
carotenoids absorbs the excessive light that can damage chlorophyll
explain the excitation of chlorophyll by light
- pigment absorbs light and goes into excited/unstable state
- electrons fall back to ground state
- electrons can be released as photons of light or heat
photons of light are described as
fluorescence
what is a photosystem
a reaction-centre complex surrounded by light-harvesting complexes
donut is light-harvesting, hole is reaction centre
what are light-harvesting complexes
pigments bound to proteins
what do light-harvesting complexes do
transfer photon energy to reaction centre
what are the components of a photosystem
reaction-centre complex
- primary electron acceptor
- special pair of chlorophyll a
light-harvesting complexes
- pigment molecules
how does a photosystem function
light harvested is transferred to the pair of chlorophyll a
electron is transferred to primary electron acceptor
what are the two types of photosystems in thylakoid membranes
PSII/P680
PSI/P700
why are they named P680 and P700
P680 because chlorophyll a absorbs wavelengths 680nm best
P700 because thats the wavelength that it absorbs at
what are the types of light reactions
linear electron flow
cyclic electron transport
what are the steps of linear electron flow (6)
light goes into PSII
2 electrons go into PSII from h2o and 2 hydrogens and 1/2 o2 are released
electrons are transported through the electron transport chain to PSI and cause an energy release
energy is used to move protons across membrane (drives atp production)
light goes into PSI
electrons fall and are transferred to NADP+ creating NADPH
which part of linear electron flow happens where
PSII -> ETC happens in the thylakoid space
PSI happens in stroma
after the linear electron flow happens what are the pH of the components of the chloroplasts
the thylakoid space is more acidic
the stroma is more basic
what are the steps of cyclic electron transport
light enters PSI
2 electrons move to the primary electron acceptor
hydrogen ions are pumped out
atp is produced
2 electrons reenter the PSI
where does the calvin cycle take place
stroma
what are the three phases of the calvin cycle
carbon fixation
reduction
regeneration of RuBP
what are the steps of carbon fixation in the calvin cycle
- 3 RuBP + 3 co2 are catalyzed by rubisco and form a c6 intermediate
- 6 PGA are formed
- 6 atp are used for their phosphate group (6 adp are released)
- 6 NADPH are used for the H (6 NADP+ and 6 inorganic phosphates are released)
what does RuBP stand for
ribulose biphosphate
c5
what does PGA stand for
phosphoglycerate acid
c3
what are the steps of reduction in the calvin cycle
- 6 G3P are formed
- 1 G3P is released
what does G3P stand for
glyceraldehyde 3-phosphate
c3
what are the steps of regeneration of RuBP in the calvin cycle
- 5 G3P are used
- 3 atp are used for their phosphate groups (3 adp are released)
- 3 RuBP are released
what type of molecule is G3P
a sugar
what is photorespiration
the interaction between RuBP and oxygen with rubisco to catalyze
how does photorespiration happen
when oxygen gas builds up and there is a limited amount of co2
due to stomata being closed on hot and dry days
details of photorespiration
oxygen is a competitive inhibitor to co2 for the active site of rubisco (o2 and co2 have similar shape)
o2 doesnt add to carbon chain so no sugar is produced during photosynthesis and plant doesnt grow, instead releases co2 with no atp
advantage and disadvantage of photorespiration
can limit damaging product of light reactions
can drain up to 50% of carbon from calvin cycle
how do c4 plants minimize the cost of photorespiration
they put co2 into a c4 compound and the increase the co2 concentrations near rubisco using distinct cell types in their leaves
types of cells in c4 plants leaves
mesophyll cells
bundle-sheath cells
steps of sugar production in c4 plants
- co2 is trapped by PEP carboxylase and creates a c4 compound (oxaloacetate) with PEP (c3) in mesophyll cell
- c4 travels to bundle-sheath cell
- c3 compound is released and co2 enters calvin cycle
what is CAM
crassulacean acid metabolism
used to fix carbon
how does CAM work
stomata open at night, co2 is incorporated into c4 organic acids
stomata close during the day, co2 is released and used in calvin cycle
