13.11 Past Paper Practise
Q1.
Q2.
(b)
Q3.
Q4.
Q5.
Q6.
Q7.
Q8.
Q9.
Q10.
Q11.
Q12.
Q13.
Q14.
Q15.
Describe the role of chloroplast pigments in light absorption. [7]
any seven from:
1 pigments arranged in light-harvesting clusters ;
2 photosystems ;
3 accessory pigments surround primary pigment ;
4 accessory pigment example ; e.g. chlorophyll b / carotene
5 primary pigment is chlorophyll a ;
6 reaction centre ;
7 accessory pigments absorb light energy ;
8 ref. to different wavelengths to chlorophyll a ;
9 pass energy on to, chlorophyll a / primary pigment / reaction centre ;
10 pigments absorb light at different wavelengths / maximising light absorbed for photosynthesis ;
Outline how the Calvin cycle produces triose phosphate and outline the conversion of triose phosphate into amino acids. [8]
any eight from:
1 carbon dioxide fixation / carbon dioxide combines with RuBP ;
2 using rubisco ;
3 6C unstable compound formed ;
4 2 x GP formed ;
5 GP reduced to TP ;
6 using ATP ;
7 and reduced NADP ;
8 from light-dependent stage ;
9 TP / GP, combines with, nitrate ions / ions containing nitrogen ;
10 ions enter via roots ;
11 ATP required ;
Q16.
The diagram below shows a vertical section through a leaf as seen under a light microscope.
(a) Name the parts A, B & C. [3]
A – vascular bundle;
B – palisade mesophyll;
C – spongy mesophyll;
(b) In which part would you find most chloroplasts? [1]
B/palisade mesophyll;
(c) The diagram below shows the electron microscope features of a chloroplast.
i) Name structures 1 to 6. [6]
1 = double membrane/envelope;
2 = granum;
3 = photosynthetic units (quantasomes) (Quantasomes are particles found in the thylakoid membrane of chloroplasts in which photosynthesis takes place. They are embedded in the surface of thylakoid discs in chloroplasts. They are composed of lipids and proteins that include various photosynthetic pigments and redox carriers.);
4 = stroma;
5 = lipid droplet;
6 = starch grain;
(ii) What reaction of photosynthesis occurs in,
1. Structure 4.
2. Structure 2. [2]
1. dark/Calvin/light independent reaction;
2. light/Hill/light dependent reaction;
Q17.
The graph below shows the effect of light intensity on photosynthesis.
(a) What is the limiting factor in region X? [1]
light intensity;
(b) What is being demonstrated at Y & Z? [3]
Y – some other factor is limiting reaction;
Z – light intensity is no longer limiting the reaction;
probably carbon dioxide concentration is now limiting;
(c) Draw a simple apparatus that you could use to investigate the effect of light intensity on an aquatic plant such as Canadian Pondweed (Elodea canadiensis). [3]
correct arrangement of beaker, funnel and test tube;
plant in correct position with end in stem of funnel;
water and oxygen bubbles correctly shown;
Q18.
The diagram below shows the ultrastructure of a chloroplast.
(a) On the diagram, label
(i) the site of the light dependent reaction of photosynthesis.
(ii) a site of the light independent reaction of photosynthesis.
(iii) a site of food storage. [3]
(i) stack of grana/thylakoid/quantasome should be labelled;
(ii) stroma should be labelled;
(iii) starch grain/oil droplet should be labelled;
(b) Radioactively labelled (14C) carbon dioxide has been used to identify the intermediate compounds in the light
independent stage of photosynthesis (Calvin cycle). Which intermediate compound would be the first to contain
the 14C? [1]
glycerate phosphate/phosphoglyceric acid/PGA;
(c) Name three chloroplast pigments. [3]
chlorophyll a;
chlorophyll b;
carotene;
phaeophytin/xanthophyll;
Q19.
The graph below shows the effect of temperature on the rate of photosynthesis in two plants, A and B.
(a) Find the rate of photosynthesis at 17oC for both plants using the graph above. [2]
A……
B……
A = 15 mmol CO2 m-2 sec-1; (allow 15.1)
B = 25 mmol CO
2 m-2 sec-1; (allow only 1 mark if no units)
(b) Which plant is likely to grow better in a cool, temperate region? Give a reason for your answer. [2]
B; because it photosynthesises faster than A up to 200C/photosynthetic rate decreases/ lower than A after 20oC;
(c) Why does photosynthesis stop at high temperatures? [1]
because the enzymes are denatured/description of denaturation;( No mark for saying “killed”.)
(d) Name two environmental factors other than temperature which limit the rate of photosynthesis. [2]
Any two of: light intensity/carbon dioxide tension/lack of water;; (not just ‘light/CO2/water’)
Q20.
The table below shows the results of an experiment in which the effect of different light intensities on the rate of photosynthesis of Canadian Pondweed was measured at two different carbon dioxide tensions. Sodium hydrogen carbonate was used as a CO2 source. The different light intensities were obtained by placing a 60 watt lamp at different distances from the plant in a darkened room. The rate of oxygen evolution was measured as an indicator of photosynthetic rate.
| Distance of lamp from plant/metres | 2.00 | 1.50 | 1.00 | 0.75 | 0.50 | 0.25 | 0.10 |
| Rate of O2 release in 1% HCO3- /mm3 min-1 A | 0.2 | 0.4 | 0.7 | 1.4 | 1.4 | 1.4 | 1.4 |
| Rate of O2 release in 2% HCO3-/mm3 min-1 B | 0.6 | 0.8 | 1.1 | 1.5 | 1.8 | 1.8 | 1.8 |
(a) Plot the results on graph paper. [5]
correct labelled axes (distance on X-axis);
suitable scale (at least half the graph paper);
accurate plotting;
points joined with a ruler (according to IOB instructions for A-Level Biology);
curves labelled;
(b) (i) Describe the relationship between light intensity and the rate of photosynthesis using curve B from your
graph. [3]
from 2 to 0.5m, the rate of photosynthesis increases;
after this increasing the light intensity has no effect on the photosynthetic rate;
CO2 tension probably limiting;
(ii) Comment on the differences shown in the rates of photosynthesis in A and B. [3]
lower rate of photosynthesis overall in A;
limiting effect in A starts at lower light intensity;
lower rate of photosynthesis in A when CO2 is limiting;
The light intensity [I] at the plant is given by the formula:
where d is the distance of the light source from the plant.
Calculate the light intensities in A and B at which the rate of photosynthesis starts to be limited. Show your working. [4]
Q21.
The diagram below shows part of the light independent reaction of photosynthesis.
(a) Identify compounds A, B and C. [3]
A – carbon dioxide;
B – ADP;
C – NADP; (B and C could be the other way round)
Where in the chloroplast does this reaction take place? [1]
stroma;
Apart from being converted to glucose, what other use has GP? [1]
can be used to regenerate RuBP;
(d) State the source of compounds B and C in the photosynthetic process. [2]
from the quantosomes/thylacoid membranes;
products of light dependent reaction/photophosphorylation;
(e) How is glucose converted to starch? [2]
polymerisation/condensation/removal of water;
joining glucose molecules by alpha-glycosidic links;
Q22.
The table below shows the results of an experiment on the production and use of sugars in the leaves of a plant.
| RATE OF SUGAR PRODUCTION/USE /arbitrary units | RATE OF SUGAR PRODUCTION/USE /arbitrary units | RATE OF SUGAR PRODUCTION/USE /arbitrary units | |
| TEMPERATURE /oC | Photosynthesis (high light intensity): | Respiration: | Net gain/loss: |
| 0 | 0 | 2 | |
| 10 | 36 | 4 | |
| 15 | 42 | 5 | |
| 20 | 72 | 6 | |
| 25 | 80 | 8 | |
| 30 | 48 | 16 | |
| 40 | 12 | 30 | |
| 50 | 0 | 20 | |
| 60 | 0 | 18 |
(a) (i) From these figures work out the net gain/loss of sugar at each temperature and write the figures in the appropriate box on the table. [2]
| Temp 0C: | Net loss/gain: |
| 0 | -2 |
| 10 | 32 |
| 15 | 37 |
| 20 | 66 |
| 25 | 72 |
| 30 | 32 |
| 40 | -18 |
| 50 | -20 |
| 60 | -18 |
;; (2 marks if all correct, penalty of 1 mark per error)
(ii) Plot the results of sugar production in photosynthesis, sugar use in respiration and net gain/loss at different
temperatures, graphically. [5]
axes labelled (temp. as X axis); suitable scale; accuracy of plotting; points joined with a ruler; curves labelled;
(b) What are the optimum temperatures for:
(i) photosynthesis.
(ii) respiration? [2]
(i) 25oC;
(ii) 40oC;
(c) (i) Define the term ‘compensation point’. [2]
the light intensity;
at which the rates of photosynthesis and respiration are the same;
ii) Use the graph to estimate the temperature at which the plant reaches its compensation point. [1]
36.5oC; (accept 36.0 to 37.0)
Q23.
The graph below shows the effect of oxygen concentration on the rate of photosynthesis.
(a) Comment on the effect of oxygen concentration on photosynthesis. [3]
oxygen is an inhibitor of photosynthesis at higher concentrations;
little or no inhibition at atmospheric concentrations;
oxygen is a competitive inhibitor of RuBP carboxylase;
The graph below shows the effect of changing the carbon dioxide concentration on the rate of photosynthesis.
(b) What conclusions can you draw from this graph? [4]
atmospheric levels of carbon dioxide are sub-optimal for photosynthesis;
rates of photosynthesis can be increased by increasing atmospheric concentration of carbon dioxide;
especially at high light intensity;
reference to principle of limiting factors;
(c) (i) Define the term “compensation point”. [2]
the light intensity;
at which the rates of photosynthesis and respiration are equal/no net gain or loss in weight;
(ii) Describe what happens when the compensation point is exceeded. . [2]
photosynthesis exceeds respiration;
thus plant gains sugar for storage;
(iii) Explain why it is of advantage for a woodland herb to have a low compensation point. [2]
dim light in wood;
thus compensation point occurs at a low light intensity so plant starts to accumulate sugar sooner;
Q24.
(a) Distinguish between each of the following pairs of photosynthetic terms.
(i) Absorption spectrum and action spectrum. [3]
absorption spectrum shows amount of light absorbed (by photosynthetic pigments) at different wavelengths;
action spectrum shows rate of photosynthesis at different wavelengths;
both have similar profiles/peaks in red and blue;
(ii) Cyclic and non-cyclic photophosphorylation. [3]
cyclic involves photosystem 1 and non-cyclic involves both photosystems 1 and 2;
cyclic generates ATP and non-cyclic generates ATP and NADPH;
non-cyclic is coupled to photolysis of water but cyclic is independent of this;
(iii) C3 and C4 plants. [3]
C3 plants produce glyceraldehyde 3 phosphate (3C) from ribulose bisphosphate and CO2;
C4 plants produce malic acid (4C) from phospho-enol pyruvic acid and CO2;
C4 plants more efficient in high O2 tensions;
(b) Describe the function of each of the following in photosynthesis:
(i) magnesium ions. [2]
magnesium ions are a component of chlorophyll;
bound onto porphyrin ring of chlorophyll;
(ii) quantosomes. [2]
large subunits on thylakoids house photosystem II;
small subunits on thylakoids house photosystem I;
Q25.
The experiment below is designed to show that sunlight is necessary for photosynthesis.
The plant is destarched by leaving it in the dark for 48 hours prior to the investigation. It is then left in the sunlight
for at least 5 hours.
(a) (i) Why is the plant destarched first? [2]
to ensure no starch is present in the plant at the beginning of the experiment;
as this is what is being tested for;
(ii) Why does the plant destarch in the dark? [2]
starch is broken down to sucrose/glucose;
and used for respiration/transported to roots/storage organ;
(b) Two leaves, A & B, are detached and tested for starch after 5 hours. Explain how you would test the two
leaves for starch. [5]
dip leaf in boiling water to kill cells;
place in boiling alcohol to remove chlorophyll;
wash in hot water to soften;
spread on a white tile and flood with iodine in potassium iodide;
blue/black indicates presence of starch;
(c) Describe the expected results of the two leaves after testing for starch. [3]
A is completely blue black, B is only blue black where there was no cover;
covered part of B remains iodine colour;
thus starch only made in areas exposed to light;
Q26.
The diagram shows the biochemical processes taking place in two plant cell organelles:
(a) Name organelles X and Y and substances A and B. [4]
X- chloroplast;
Y- mitochondrion;
A- oxygen;
B- carbon dioxide;
(b) Oxidative phosphorylation occurs in organelle Y and photophosphorylation occurs in organelle X. Outline the
difference between oxidative phosphorylation and photophosphorylation. [6]
oxidative phosphorylation uses energy from oxidation;
of reduced coenzymes/NADH;
to produce ATP;
photophosphorylation involves using light energy;
to produce ATP;
and reduced NADP/NADPH;
(c) (i) The light reaction produces ATP and NADPH, which are used in the dark reaction. What are they used for in the dark reaction? [2]
ATP used as energy supply for CO2 fixation in the dark/Calvin reaction;
NADPH used as reducing power when CO2 is converted to carbohydrate in dark/Calvin reaction;
(ii) State two uses of ATP produced in plants. [2]
ATP is needed for many synthetic chemical reactions;
and processes such as active transport;
Q27.
Read through the following account of photosynthesis and then complete it by inserting the most appropriate word
or words into the spaces.
There are three pigments commonly found in the chloroplasts of flowering plants. These are chlorophyll a, chlorophyll b and ………………………………. . Chlorophylls absorb mainly …………………….. and ……………………… wavelengths of light. During cyclic photophosphorylation the absorption of light causes the displacement of an electron from the chlorophyll molecule. This electron is returned to the chlorophyll via a series of ……………………. which are at progressively lower energy levels. Coupled with this electron flow is the synthesis of ……………. This compound is then used in the light independent reaction which occurs in the …………………………………… region of the chloroplast. During non-cyclic photophosphorylation, the electron is combined with ………………….. ions resulting from the photolysis of ………………………… to form the reduced coenzyme called ………………………
This reduced coenzyme is used in the ……………………………. cycle to convert ……………………………………… acid to phosphoglyceraldehyde (PGAL). This can be converted to ……………………………………….. which is the acceptor molecule for the carbon dioxide used in photosynthesis. The electron emitted from the chlorophyll molecule is replaced by electrons from the …………………………………………. ions produced by photolysis. As a result ………………………………. gas is liberated. [14]
carotene;
red; blue; {the order is not important, as long as two different colours are written}
electron carriers;
ATP;
stroma;
hydrogen;
water;
NADPH;
Calvin; phosphoglyceric;
ribulose bisphosphate;
hydroxide;
oxygen;
(b) Explain why plants need a healthy root system to photosynthesise. [2]
water absorbed by roots is a reactant/supplies electrons/H;
for uptake/transport of minerals/needed for turgidity;
Q28.
Suggest explanations for each of the following:
(a) Leaves in the tops of beech trees have two or three layers of palisade mesophyll cells, but the leaves lower down only have one layer of palisade mesophyll cells. [3]
more light at top of tree than at bottom which is shaded;
thus more chloroplasts needed at top and so more palisade cells/fewer chloroplasts needed in shade
/comment on adaptation to microclimates;
possibly lower leaves cannot make enough food to enable growth of extra cells/lower leaves have less nutrition;
(b) Peas and beans tend to contain much higher concentrations of protein than cereals. [2]
peas and beans contain Rhizobium/root nodules for nitrogen fixation;
thus can make more protein;
(c) Power stations frequently have adjacent man-made lakes containing algae, such as Chlorella. [3]
waste carbon dioxide produced by power station is bubbled through lake;
assimilated by Chlorella for growth and reproduction;
Chlorella is harvested for use as cattle food/reduces CO2 emission and greenhouse effect;
Q29.
The graph below shows results of investigations into the mechanism of stomatal opening.
(a) Describe the relationship between stomatal aperture width and starch concentration between:
(i) 8.00 am and noon. [1]
stomatal width increases as concentration of starch decreases;
(ii) 4.00 pm and 8.00 pm. [1]
stomatal width decreases as concentration of starch increases;
(b) (i) Using information from the graph and your own knowledge, suggest a mechanism for stomatal opening. [4]
light stimulates conversion of starch to sugars;
therefore as light intensity increases, starch decreases;
sugars reduce water potential of guard cells;
water enters osmotically;
as guard cells swell, stomatal pore opens;
ref uneven thickening of guard cell walls;
(ii) How might the width of stomatal aperture differ from the above, if the plant was in dry conditions during
the 12 hour period? Explain your answer. [2]
closed/reduced aperture;
deficit of water means guard cells cannot absorb any and so cannot swell;
(c) Describe one technique which can be used to measure the stomatal density on the underside of a leaf. [3]
peel off epidermis/make a varnish imprint;
use low power light microscope and eyepiece micrometer;
count number of stomata in a square mm;
Q30.
A drop of water containing a strand of the green algae, Spirogyra, and some free living aerobic bacteria were mounted on a microscope slide. The slide was then illuminated with light which was split into its constituent colours (wavelengths) using a prism. The figure shows the distribution of bacteria after a few minutes.
(a) Describe the distribution of bacteria. [1]
most bacteria in red light and blue light/400-450 nm and 650-700 nm/few in yellow-green areas/equivalent;
(b) Suggest an explanation for the distribution of bacteria. [3]
bacteria congregate where oxygen concentration is greatest;
oxygen released in photosynthesis;
these are the most effective (wavelengths) in photosynthesis;
(c) Chloroplasts contain several pigments. What is the significance of this in photosynthesis? [3]
each pigment absorbs different wavelengths/parts of visible spectrum/has different absorption maxima;
accessory pigments/carotene/xanthophyll become excited/energised;
and pass excited electrons onto chlorophylls;
therefore leaves/plants are able to absorb more/a lot of light;
Q31.
The graph shows the effect of light on the uptake and release of carbon dioxide of a green plant.
(a) Outline the significance of light intensity X. [2]
compensation point;
light intensity at which CO2 uptake = CO2 output/rate of photosynthesis equals rate of respiration;
plant can only gain mass/grow when X is exceeded;
(b) Explain the shape of the graph at Y. [2]
increasing light intensity stimulates light dependent stage/stimulates cyclic/non-cyclic photophosphorylation;
some other factor becoming limiting/slowing rate of reaction;
such as carbon dioxide concentration;
(c) (i) List the products of the light reaction. [3]
oxygen;
NADPH;
ATP;
(ii) Outline how products of the light dependent stage are used in the light independent stage of photosynthesis. [2]
ATP provides energy for conversion of PGA to TP;
NADPH provides hydrogen/H atoms/reducing power for conversion of PGA to TP;
Q32.
The graph shows the results of an investigation into the uptake and release of carbon dioxide by an aquatic green unicellular alga, such as Chlorella.
(a) Calculate the mean uptake of carbon dioxide over a six hour period in the light. [2]
(b) Which of the two lines, X or Y, represent gross CO2 use in photosynthesis? Explain your answer. [3]
Y;
CO2 absorbed in light;
plus CO2 released in respiration (in light); (Reject respiration in dark -it is not photosynthesising in the dark)
(c) For period A express the net photosynthesis as a percentage of the gross photosynthesis. Assume the respiration rate to be the same as in the previous dark period. Show your working. [2]
(d) Waste gases containing CO2 from power stations are sometimes pumped through pools containing Chlorella.
Explain two benefits of this. [4]
Chlorella absorbs CO2 to make biomass;
this can be sold as cattle fodder/food/fertiliser;
Chlorella absorbs CO2 and so reduces greenhouse effect;
reduces global warming/eq. ;
Q33.
(a) State the main function of each of the following mineral ions in a healthy plant.
(i) nitrate. [1]
amino acid/protein/DNA/RNA/nucleotide synthesis;
(ii) phosphate. [1]
carries energy in form of ATP/ref. to photophosphorylation;
(iii) magnesium. [1]
component of chlorophyll molecules/component of middle lamella (of cell wall);
(b) What is meant by the term ‘limiting factor’? [2]
factor which limits/restricts the rate of a process/named metabolic process;
that factor which is closest to its minimum value;
In an investigation to determine the optimum application of nitrogen fertiliser to barley, trials were conducted in two fields. One of the fields had previously received high applications of phosphate fertiliser. The second field had previously received a low application of phosphate fertiliser. The graph shows the results of the investigation.
(c) (i) State the effect of phosphate levels on the yield of barley. [1]
higher phosphate increases yield;
(ii) Determine the optimum nitrogen application in the field which has received high phosphate. [1]
60 (59-61) kg ha-1;
(d) (i) State one possible harmful environmental consequence of adding too much nitrogen fertiliser. [1]
leaching out into water contributing to eutrophication/blue baby syndrome/may increase risk of stomach cancer if
converted to nitrosamines;
Q34.
A student investigating chlorophyll pigments set up the apparatus shown in the figure below.
(a) Outline how the student would have obtained the chlorophyll spot. [4]
cut up leaves and macerate/grind up;
suitable solvent/acetone/acetone ether mixture;
micropipette on to paper repeatedly;
allow to dry each time/use of hair dryer;
(b) State two precautions which should be taken in setting up this investigation. [2]
Any two of:
use pencil line, not ink/pen/
do not allow solvent to touch line/
seal/allow time to achieve saturated atmosphere in tube/
do not allow paper to touch sides/avoid contamination by substances on fingers/
keep cold/in dark;;
(c) Chlorophyll contains a number of pigments. Explain the biological significance of this. [2]
different pigments absorb different wavelengths/parts of visible spectrum;
greater amount of light absorbed/faster photosynthesis;
Q35.
A student used paper chromatography to separate the pigments from a sample of petals. The procedure followed by the student is shown in the diagram below.
(a) State one precaution which the student should have taken in this investigation. [1]
ensure pigment spot is above solvent/ensure atmosphere in container was saturated with solvent before running;
(b) Outline the chemical principle illustrated by this technique. [2]
solutes/pigments dissolve in solvent;
solvent moves up paper;
distance moved by solutes/pigments depends on their relative solubility/molecular size;
The table shows the distance moved by the solvent and pigments.
| Substance: | Distance moved (mm): |
| Solvent front Pigment A Pigment B Pigment C | 93 18 35 36 |
(c) (i) Define the term Rf value. [2]
relative flow (Rf) is a physical constant;
for a specific solute in a specific solvent;
it is the distance moved by the solute divided by the distance moved by the solvent (front);
(ii) Calculate the Rf values for pigments B and C. Show your working. [2]
(iii) Suggest one way by which greater separation of pigments B and C could have been achieved. [1]
2-way chromatography/run with a different solvent;