photosynthesis exam qs Flashcards
in photosynthesis, which chemicals are needed for the light dependent reaction? (1 mark)
a) reduced NADP, ADP, Pi water and oxygen
b) NADP ATP and water
c) reduced NADP, ATP, water and carbon dioxide
d) NADP, ADP, Pi and water
NADP, ADP, Pi and water
describe what happens during photoionisatiom in the light dependent reaction? (2 marks)
M1: chlorophyll absorbs light
M2: light excites electrons in chlorophyll
explain why the student marked the origin using a pencil rather than using ink (1 mark)
ink and leaf pigments would mix
describe the method the student used to separate the pigments after the solution of pigments had been applied to the origin (2 marks)
M1: level of solvent below origin
M2: Remove before solvent reaches the top
The pigments in leaves are different colours. Suggest and explain the advantage of having different coloured pigments in leaves (1 mark)
absorbs different wavelengths of light for photosynthesis
Heat stress decreases the light dependent reaction of photosynthesis.
Explain why this leads to a decrease in the light independent reaction (2 marks)
M1: less ATP
M2: less reduced NADP
A decrease in the activity of the enzyme rubisco would limit the rate of photosynthesis
Explain why. (2 marks)
M1: less carbon dioxide reacts with RuBP
M2: less GP
Where precisely is rubsico found in a cell? (1 mark)
stroma
the scientists concluded that heat stress reduces the activity of rubisco in plant leaves by affecting rubisco activase.
Use all the information to evaluate their conclusion. (4 marks)
M1: rubsico activity increases with temperature
M2: rubsico activase activity decreases at high temperatures
M3: results suggest activase does not affect activity of rubsico
M4: no stats test done
The solution that the student used to produce the chloroplast suspension had the same water potential as the chloroplasts. Explain why it was important that these water potentials were the same (2 marks)
M1: osmosis does not occur
M2: chloroplasts does not burst
explain why the student set up Tube 1 (2 marks)
M1: to show light does not affect DCPIP
M2: to show chloroplasts are required
Explain the results in tube 3 (2 marks)
M1: reduction of DCPIP by electrons
M2: from light dependent reaction
Explain the advantage of the student using the IC50 in this investigation (1 mark)
can compare different concentrations of weed killers
Explain how chemicals which inhibit the decolorisation of DCPIP could slow the growth of weeds (2 marks).
M1: less ATP produced
M2: less reduced NADP produced
Explain why the scientists measured the rate of production of oxygen in this investigation (2 marks)
M1: oxygen produced in light dependent reaction
M2: the fasted oxygen is produced, the fasted the light dependent reaction
The scientists suggested that mutant plants producing more chlorophyll b would grow faster than normal plants in all light intensities
Explain how these data support this suggestion. (4 marks)
M1: have fast production of ATP and reduced NADP
M2: so have faster light independent reaction
M3: so produce more sugars that can be used in respiration
M4: so more energy for growth
other than the thermometer, explain how two features of the calorimeter shown in the diagram above would enable a valid measurement of the total heat energy released. (2 marks)
M1: stirrer distributes heat energy
M2: water has high specific heat capacity
In natural ecosystems, most of the light falling on producers is not used in photosynthesis
Suggest two reasons why (2 marks)
M1: light misses chlorophyll
M2: light is wrong wavelength
The light absorbed by chlorophyll is used in the light dependent reaction.
Name the two products of the light dependent reaction that are required in the light independent reaction (2 marks)
M1: ATP
M2: reduced NADP
A teacher studying these data with her students told her class that no definite conclusions could be drawn when comparing the mean values in the graph
Suggest why the teacher said this (2 marks)
M1: no standard deviation bars
M2: to show if overlap occurs so difference in means is significant
Atrazine bind to proteins in the electron transfer chain in chloroplasts of weeds, reducing the transfer of electrons down the chain.
Explain how this reduces the rate of photosynthesis in weeds. (4 marks)
M1: reduced transfer of protons across thylakoid membrane
M2: so less ATP produced
M3: so less reduced NADP produced
M4: so light independent reaction stops
When treated with atrazine, weeds have been shown to give off small amounts of heat
Suggest an explanation for this observation. (1 mark)
energy is released from excited electrons that were lost from chlorophyll
Suggest the purpose of each of the three leaf treatments (3 marks)
M1: no grease means stomata are open
M2: grease on lower surface means stomata is sealed
M3: grease on both surfaces means all CO2 uptake is stopped
describe the results shown for treatment 1 (2 marks)
M1: mean rate of carbon dioxide uptake was constant and fell after the light turned off
M2: uptake fell from 4.5 to 0
The stomata close when the light is turned off.
Explain the advantage of this to the plant (2 marks)
M1: because water is lost through stomata
M2: closure prevents water loss
Treatment 2 shows that even when the lower surface of the leaf is sealed there is still some uptake of carbon dioxide
Suggest how this uptake of carbon dioxide continues (1 mark)
carbon dioxide uptake through the upper surface of the leaf
In both treatment 1 and treatment 2 the uptake of carbon dioxide falls to zero when the light is turned off.
Explain why. (2 marks)
M1: no use of carbon dioxide in photosynthesis in the dark
M2: no diffusion gradient maintained for carbon dioxide into leaf
What measurements should the student have taken to determine the rate of photosynthesis?
(1 mark)
oxygen concentration
Other than temperature and pH, give two factors which should be kept constant during this investigation (2 marks)
M1: light intensity
M2: time
The student did not use a buffer to maintain the pH of the solution. Explain what would happen to the pH of the solution during this investigation. (2 marks)
M1: pH increases
M2: more carbon dioxide removed for photosynthesis
Suggest and explain why the rate of photosynthesis was low between 525nm and 575nm wavelengths of light. (2 marks)
M1: less absorption of these wavelengths of light
M2: light required for light dependent reaction
Name the process that resulted in the development of woodland from farmland (1 mark)
succession
Explain the increase in diversity of birds as the woodland developed (3 marks)
M1: greater variety of plants
M2: more food sources
M3: more habitats
Give two factors which could be limiting the rate of photosynthesis in the sun plant between points A and B on the figure (1 mark)
temperature and carbon dioxide
Explain why CO2 uptake is a measure of net productivity. (1 mark)
shows gross productivity minus respiration
Use the information in the figure to explain how the shade plant is better adapted than the sun plant to growing at low light intensities (2 marks)
M1: shade plant has lower rate of respiration
M2: greater net productivity
