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Where in the chloroplast does the light dependent stage occur?
in the thylakoids
Where in the chloroplast does the light-independent stage of photosynthesis occur?
he stroma
Why are there many different photosynthetic pigment
Each pigment absorbs light most efficiently at specific wavelengths. Having multiple pigments allows capture of more energy, compared to having just one pigment
Which photosynthetic pigment is found in all photosynthetic plants?
chlorophyll a
Which colours of light do chlorophyll pigments absorb, and which do they reflect?
Chlorophyll a and b absorb red light (wavelength 650-700 nm) and blue light (wavelength 400-450 nm). They reflect green light (500-550nm).
Plants containing carotenoid pigments (xanthophyll and carotene) tend to be which colours?
Red, orange and yellow. The carotenoids absorb blue light and reflect red, orange and yellow. These pigments give carrots, tomatoes and egg yolk colour
Explain the difference between an absorption spectrum and an action spectrum.
Absorption spectrum measures which wavelengths of light are absorbed by the pigments. An action spectrum measures the rate of photosynthesis at diff wavelengths
Name the technique used to separate chloroplast pigments.
chromatography
How is the Rf value calculated in chromatography?
distance travelled by the pigment/distance travelled by the solvent
Define photoactivation
process where two electrons in the chlorophyll molecule become excited (due to absorption of light energy) causing them to leave the molecule.
What happens to the electrons that leave the chlorophyll molecule during photoactivation?
Two electrons are taken up by an electron acceptor. They move down electron carriers within the thylakoid membrane in the ETC and release energy as they go
How is the energy from the ETC used in the light-dependent stage?
it is used to pump two H+ ions from the stroma into the thylakoid space. This creates a H+ gradient across the thylakoid membrane
How is the H+ gradient used to make ATP?
H+ exit the thylakoid membrane through ATP synthase which catalyses the formation of ATP using the energy in the H+ gradient. NADP accepts H+ and gets reduced
What happens to water during the light-dependent stage of photosynthesis?
Water is split using light energy (photolysis). 2H2O → 4H+ + 4e- + O2
State what happens to the products of the photolysis of water.
H+ taken up by NADP, e- replace those lost by the chlorophyll during photoactivation, O2 given off as waste product
What are the two important products of the light-dependent stage that are used in the light-independent stage?
ATP and reduced NADP- these compound transfer energy from the light-dependent stage which is used later
