photosynthesis Flashcards
what are the substances which attach to the thylakoid membrane?
photosystems containing photosynthetic pigments such as chlorophyll and carotenoids, electron carriers, enzymes like NADP+ reductase and ATP synthase (stalked particle)
where does the light reaction take place?
thylakoid membrane (including grana and intergranal lamella)
where does the dark reaction/ Calvin Cycle take place?
stroma
what are the photosystems embedded in the thylakoid membrane (there are two)
PSI = PS700
PSII = PS680
what are the components of a photosystem?
light harvesting complex (LHC) and a reaction centre (RC)
what are the pigments found in the light harvesting complex (LHC)?
accessory pigments such as chlorophyll a , chlorophyll b and carotenoids
what is the final electron acceptor in non-cyclic photophosphorylation?
NADP+ which forms NADPH cataylsed by NADP+ reductase
what are the functions of these pigments?
absorb light energy between 400-700 nm and transfer the energy to the RC
outline the steps of non-cyclic photophosphorylation
- PSII containing photosynthetic/accessory pigments (chlorophyll a, chlorophyll b and carotenoid) absorbs light energy in the LHC
- light energy is passed down neighbouring pigments until it reaches a pair of special chlorophyll a in the RC
- photoactivation of special chlorophyll a causes an electron to be displaced
- displaced electron is accepted by the primary electron acceptor
- photolysis of water occurs to replenish the displaced e-
H+ accumulates in the thylakoid space
2H2O(l)→4H++4e−+O2(g) - the electron is then passed down electron carriers of decreasing energy levels of the first ETC from PSII to PSI, until it reaches a pair of special chlorophyll a in the RC of PSI
- the energy released from the flow of electrons is used to pump protons (H+) from the stroma to the thylakoid space
a steep proton gradient is thus established as the thylakoid membrane is impermeable to ions due to the hydrophobic core and H+ accumulate in the thylakoid space - photoactivation of special chlorophyll a occurs simultaneously in PSI, resulting in an electron being displaced
- the electron displaced from the PSI is passed down electron carriers of decreasing energy levels of the second ETC
- the electron is accepted by the final electron acceptor NADP+ to form NADPH which is catalysed by NADP+ reductase
- diffusion of H+ from the thylakoid space to the stroma through the hydrophilic channel of ATP synthase (stalked particle) down a concentration gradient releases energy
12.which is coupled to ATP synthesis, catalysed by ATP synthase (chemiosmosis)
what does the RC consists of?
primary pigments (special chlorophyll a)
what is Photosynthetically Active Radiation (PAR)?
light energy from a range of 400-700 nm
what colour of light brings about a high rate of photosynthesis?
blue and red
what wavelength of visible light is not absorbed? (colour)
green
direction of diffusion of H+
from thylakoid membrane to the stroma
describe the formation of a steep proton gradient
energy released from the flow of electrons of the first ETC is used to pump H+ from the stroma to the thylakoid space, resulting in the accumulation of H+ in the thylakoid space as the thylakoid membrane is impermeable to ions due to it hydrophobic core
