photosynthesis Flashcards
what are the main stages in the light dependent stage in photosynthesis-describe and explain them
1.photolysis- splitting of water using light energy(electrons, protons and oxygen)
2.photoionisation of chlorophyll-light energy is absorbed by the chlorophyll and the energy results in electrons becoming EXCITED and raising up energy levels to leave chlorophyll- chlorophyll has been ionised by light
3.production of ATP and reduced NADP( happens in chemiosmosis)
4.chemiosmosis-excited electrons get picked up by an electron carrier and go along an ELECTRON TRANSFER CHAIN and go across protein proton pumps which they GIVE some energy to the proton pump to ACTIVELY pump protons into the thylakoid space- series of REDOX reactions, each new carrier is a slight lower energy than the previous.
Charged protons travel down an ELECTROCHEMICAL GRADIENT through the enzyme ATP synthase- result in production of ATP as this cause a change in shape of the protein which provides the energy to catalyse ADP + Pi = ATP
some of the protons that diffused through ATP synthase will be reused and pumped back into the thylakoid space but some of the PROTEINS in the chloroplast stroma are PICKED UP by the COENZYME NADP as well as it picks up the electrons at the end of the electron transfer chain and this causes it to become REDUCED NADP
explain the stages of the light independent reaction/Calvin Cycle
1) CO2 reacts with Ribulose Bisphosphate (RuBp), this reaction is catalysed by the ENZYME RUBISCO. This creates 2x Glycerate phosphate molecules (GP)
2) The REDUCED NADP from the light dependent reaction is used to REDUCE Gp to Triose Phosphate and the energy for this provided by ATP from the LDR
3) Some Triose phosphate can be regenerated back into Ribulose bisphosphate with the used of the hydrolysis of ATP
4) Some Triose Phosphate is converted to useful organic substances (e.g glucose)
where does the light independent and dependent reaction occur in the chloroplast
Light Dependent-Occurs on thylakoid membranes or grana
Light Independent- Stroma, this fluid contains the enzyme Rubisco which means that this stage is temperature sensitive
What are the products of the light dependent and independent reaction
Light dependent-Reduced-NADP, ATP & oxygen
Light independent -NADP, ATP
what are the 2 processes of the light captured in the Light-dependent reaction
- Photolysis of water
2. Add an inorganic phosphate molecule for ADP to convert to ATP
Some plants are more shade tolerant than others e.g.
forest floor plants.
These plants will have different concentrations of the
different pigments to shade-intolerant plants.
Explain why
Answer: to absorb a different range of light wavelengths to ensure photosynthesis can continue with those wavelengths left behind after other plants above have absorbed the other wavelengths.
use of chromatography to investigate the pigments isolated from leaves of different plants, e.g., leaves from shade-tolerant and shade-intolerant plants or leaves of different colours.
why in the practical did you use a organic solvent,instead of water.
and state the controls of this practical
Water can’t be used since the pigments are hydrophobic
Use the same volume of the solvent
Make sure the solvent is below the origin.
Make sure the chromatogram is removed before the solvent reaches the top.
The more soluble a pigment is in the solvent, the further it travels.
use of chromatography to investigate the pigments isolated from leaves of different plants, e.g., leaves from shade-tolerant and shade-intolerant plants or leaves of different colours.
why in the practical did you use a organic solvent,instead of water.
and state the controls of this practical
Water can’t be used since the pigments are hydrophobic
Use the same volume of the solvent
Make sure the solvent is below the origin.
Make sure the chromatogram is removed before the solvent reaches the top.
The more soluble a pigment is in the solvent, the further it travels.
Investigation into the effect of a named factor on the rate of dehydrogenase activity in extracts of chloroplasts (the Hill reaction).
1) Why did the solution used to produce the chloroplast suspension have the same water potential as the chloroplasts?
2) Why was the solution ice cold at the start?
3) any control tubes e.g. why have a DCPIP tube in the light with no chloroplasts?
4) why is DCPIP decolourised
1) to make sure that OSMOSIS didn’t occur so that the CHLOROPLAST don’t burst or shrivel
2)To slow enzyme action and prevent damage to the chloroplasts before the experiment begins.
3)Shows that light does not directly affect DCPIP and that chloroplasts are needed.
4)DCPIP is reduced by electrons from the light dependent reaction of photosynthesis (artificial
NADP substitute).
Some species of seaweed are submerged in water for most of the time. Explain how being under water might affect the rate of photosynthesis.(3 marks)
effect; detail; effect on photosynthesis; some effects are less light / light absorbed by water different wavelength of light temperature availability of carbon dioxide availability of water
(more than one effect award 1 mark only)
