T5 Energy transfer in and between organisms Flashcards
1 mark
In photosynthesis, which chemicals are needed for the light-dependent reaction?
☑ NADP, ADP, Pi and water;
2 marks
Describe what happens during photoionisation in the light-dependent reaction.
1. Chlorophyll absorbs light
OR
Light excites/moves electrons in chlorophyll;
Ignore photosystems.
2. Electron/s are lost
OR
(Chlorophyll) becomes positively charged;
Ignore site/molecule from where electrons are lost.
Accept electrons go to electron transport/carrier chain for ‘electrons lost’.
A student obtained a solution of pigments from the leaves of a plant. Then the student used paper chromatography to separate the pigments. Explain why the student marked the origin using a pencil rather than using ink. 1 mark
Describe the method the student used to separate the pigments after the solution of
pigments had been applied to the origin. 2 marks
Ink and (leaf) pigments would mix
OR
(With ink) origin/line in different position
OR
(With pencil) origin/line in same position
OR
(With pencil) origin/line still visible;
1. Level of solvent below origin/line;
Reject water or any named aqueous solution.
Accept named organic solvent.
2. Remove/stop before (solvent) reaches top/end;
1 mark
The pigments in leaves are different colours. Suggest and explain the advantage of having
different coloured pigments in leaves.
(Absorb) different/more wavelengths (of light) for photosynthesis;
Accept wider/larger range of wavelengths.
Accept frequency for wavelength.
Accept light-dependent reaction /photophosphorylation /photoionisation
for photosynthesis.
2 marks
Heat stress is a condition that often occurs in plants exposed to high temperatures for a
prolonged period of time. Heat stress is a major factor in limiting the rate of photosynthesis.
Heat stress decreases the light-dependent reaction in photosynthesis.
Explain why this decreases the light-independent reaction. 2 marks
- (Less/no) ATP;
- (Less/no) reduced NADP;
Accept NADPH, NADPH + H, NADPH2 NADPH + H+
Reject reduced NAD, NADH etc,
2 marks
Heat stress is a condition that often occurs in plants exposed to high temperatures for a
prolonged period of time. Heat stress is a major factor in limiting the rate of photosynthesis.
Another effect of heat stress is a decrease in the activity of the enzyme rubisco. A
decrease in the activity of an enzyme means that the rate of the reaction it catalyses
becomes slower.
A decrease in the activity of the enzyme rubisco would limit the rate of photosynthesis.
Explain why
- (Less/no) carbon dioxide (reacts) with RuBP;
- (Less/no) GP;
1 mark
Where precisely is rubisco found in a cell?
- Stroma (of/in chloroplast);
Reject: stoma
Reject stroma of cytoplasm/chlorophyll
Reject stroma of mitochondrion
Ignore references to Calvin cycle or the light-independent reaction
4 marks + 1 mark
Atrazine binds 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
When treated with Atrazine, weeds have been shown to give off small amounts of heat.
Suggest an explanation for this observation.
- Reduced transfer of protons across thylakoid membrane
OR
Reduced chemiosomotic gradient / proton gradient across thylakoid membrane; - (So) less ATP produced;
- (So) less reduced NADP produced;
Accept NADPH / NADPH2 / NADPH+
Reject reduced NAD - (So) light-independent reaction slows / stops;
OR
Less reduction of GP to triose phosphate.
Idea that energy is released from high energy / excited electron/s (that were lost from
chlorophyll)
Crops use light energy to produce photosynthetic products.
Describe how crop plants use light energy during the light-dependent reaction 5 marks
- Excites electrons / electrons removed (from chlorophyll);
Accept: higher energy level as ‘excites’. - Electrons move along carriers/electron transfer chain releasing
energy;
Accept: movement of H+
/protons across membrane releases
energy.
Reject: ‘produces energy’ for either mark but not for both. - Energy used to join ADP and Pi to form ATP;
Reject: ‘produces energy’ for either mark but not for both.
Accept: energy used for phosphorylation of ADP to ATP
Do not accept P as Pi but accept phosphate. - Photolysis of water produces protons, electrons and oxygen;
- NADP reduced by electrons / electrons and protons / hydrogen;
Accept: NADP to NADPH (or equivalent) by addition of
electrons/hydrogen.
Do not accept NADP reduced by protons on its own
After harvesting, the remains of crop plants are often ploughed into the soil.
Explain how microorganisms in the soil produce a source of nitrates from these remains 5 marks
- Protein/amino acids/DNA into ammonium compounds /
ammonia;
Accept: any named nitrogen containing compound e.g. urea. - By saprobionts;
Accept: saprophytes. - Ammonium/ammonia into nitrite;
- Nitrite into nitrate;
- By nitrifying bacteria/microorganisms;
Reject: nitrifying bacteria in root nodules.
1, 3 and 4. Accept: marks for conversion even if incorrect type of
bacteria named as being involved.
2 and 5. Reject: marks for type of bacteria if linked to incorrect
process e.g. nitrite converted to nitrate by saprobionts.
3 and 4. Accept: for one mark ammonia/ammonium into nitrate if
neither mark point 3 or 4 awarded.
Note: there are no marks for the role of nitrogen-fixing bacteria as
the question refers to producing a source of nitrates from the remains of crops.
Explain the relationship between stomatal opening and photosynthesis. 2 marks
- Stomata allow uptake of carbon dioxide;
- Carbon dioxide used in / required for photosynthesis;
Describe the process of glycolysis. 4 marks
- Phosphorylation of glucose using ATP;
- Oxidation of triose phosphate to pyruvate;
Accept removal of hydrogen from triose phosphate for oxidation. - Net gain of ATP;
Accept any description that indicates a net gain e.g., 4 produced, 2
used. - NAD reduced;
Accept NADH/NADH2/NADH + H+
produced.
Accept all mark points in diagrams.
Malonate inhibits a reaction in the Krebs cycle.
Explain why malonate would decrease the uptake of oxygen in a respiring cell. 2 marks
- Less/no reduced NAD/coenzymes
OR
Fewer/no hydrogens/electrons removed (and passed to electron transfer
chain);
Accept less/no FAD reduced. - Oxygen is the final/terminal (electron) acceptor;
Where in a cell does glucose turn into pyruvate occur?
Cytoplasm/cytosol;
The Respiratory Quotient (RQ) can provide information on the type of respiration taking
place in an organism. The following equation is used to calculate the RQ.
RQ=Vol of CO2 produced during respiration/Vol of O2 used during respiration
What would be the RQ for aerobic respiration of glucose? 1 mark
A student calculated that the RQ of germinating seeds was 1.8.
Use the information provided to explain this result. 2 marks
1/one/1.0;
1. Aerobic and anaerobic respiration occurring;
Accept: some/mainly anaerobic respiration occurring.
2. More carbon dioxide produced than oxygen uptake;