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Title: Biology Edexcel unit 4 photosynthesis
Description: past paper questions and answers
Description: past paper questions and answers
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Photosynthesis
1
...
The first of these involves the
light-dependent reactions
...
Place a cross in the box next to the term that completes each
statement correctly
...
(3)
...
...
(c) In an investigation, wheat plants were grown using artificial lighting
...
When the wheat plants were mature, the total biomass of the
plants and the mass of the grain (seeds) they produced were measured for each type of
lighting
...
(i) Calculate the grain yield, as a percentage of total biomass, for the wheat grown under
metal halide lamps
...
(2)
Answer
...
(3)
...
...
...
(Total for Question 1 = 13 marks)
2
...
The total
energy used in this synthesis is known as the gross primary productivity (GPP)
...
(june 2010)
(2)
...
...
4 × 106 J m–2 year–1
...
7 × 106 J m–2 year–1 of this energy in metabolic processes
...
(i) Explain what is meant by the unit J m–2 year–1
...
...
Show your working
...
%
(iii) Place a cross in the box next to the metabolic process that best describes the
process that accounts for most of the difference between GPP and NPP in plants
...
(6)
...
...
...
...
(iii) Suggest two advantages of growing crops of wheat in glasshouses with artificial
lighting rather than growing them in open fields
...
(Total for Question 2 = 12 marks)
1
3
...
(Jan 2011)
(a) The following statements are about carbon fixation
...
(1)
A The light-dependent reactions of the Calvin cycle
B The light-independent reactions of the Calvin cycle
C The light-dependent reactions of the Krebs cycle
D The light-independent reactions of the Krebs cycle
(ii) Place a cross in the box next to the enzyme that catalyses carbon fixation
...
(1)
A Cristae of a mitochondrion
B Granum of a chloroplast
C Matrix of a mitochondrion
D Stroma of a chloroplast
(b) Varieties of the crop plant, maize (Zea mays), are grown in many countries which
have relatively long, warm growing seasons
...
A typical corn cob is shown in the photograph below
...
(iii) The table below shows the range of temperatures for the main crop-growing season
for maize, in four regions of the World
...
Using the data shown in the graph, complete the table by selecting the most suitable
maize variety for Central Europe
...
(5)
...
...
(i) Suggest why the development of corn cobs, suitable for producing cereal products,
depends on the rate of carbon fixation in maize plants
...
...
...
In order to meet this demand, new varieties of maize have been
developed from older traditional varieties by scientific breeding programmes
...
The rate of carbon fixation is higher at 25°C than at 14°C for each of the six varieties of
maize
...
(2)
...
...
In seaweeds that are found on shores around Britain, photosynthesis occurs during
the time that they are submerged at high tide
...
Seaweeds found lower down
the shore are submerged for longer periods in deeper water
...
(i) Complete the diagram to show the structures involved in the light-dependent
reactions of photosynthesis
...
(2)
(ii) The table below shows two statements taken from a student’s essay about the lightdependent reactions of photosynthesis
...
(2)
...
2
(iii) Explain how oxygen is produced during the light-dependent reactions of
photosynthesis
...
Describe the structures in a chloroplast that are involved in this reaction
...
...
...
(b) As light penetrates deeper water, red, orange and yellow wavelengths are absorbed
by the seawater, whereas in shallow water most wavelengths penetrate
...
The relative rates of photosynthesis are compared with the rate in light with a wavelength
of 660 nm (red)
...
...
(c) The energy released by reaction S is used to form GALP (glyceraldehyde 3phosphate) during the Calvin cycle
...
Suggest how GALP may be used to synthesise cellulose
...
...
Place a tick () in the most appropriate box in each column
...
...
...
(4)
...
...
...
The diagram below summarises the interconversion of ATP and ADP
...
1
...
(June 2012)
(a) Place a cross in the box next to the region of the chloroplast that would be
involved in the fixation of carbon dioxide
...
Cells of a unicellular alga were suspended in a
solution containing 1
...
After 250 seconds, the carbon dioxide in
the solution was reduced to 0
...
The cells were illuminated with a bright light and some were removed at regular
time intervals for 500 seconds
...
(i) Suggest two reasons why a suspension of cells of a unicellular alga, in a
solution, is more suitable for this investigation than using leaves
...
...
(i) Substance W
A carbon dioxide
B an electron
C inorganic phosphate
(ii) Reaction S
A carboxylation
B hydrolysis
C phosphorylation
(iii) Reaction T
A carboxylation
B hydrolysis
C phosphorylation
(3)
...
(ii) Suggest why it would be advisable to illuminate the cells at a high light intensity during
this investigation
...
3
...
...
...
...
Describe and suggest an explanation for the changes in the concentrations of RuBP and
GP shown in the graph
...
...
(b) An investigation was carried out by a student, to find the effect of temperature on
the rate of photosynthesis in Elodea canadensis (Canadian pondweed)
...
This was repeated at different temperatures
...
The results of this investigation are shown in the graph below
...
(1)
A increase in mass of Elodea
B mass of nitrate absorbed
C volume of carbon dioxide produced
D volume of oxygen produced
...
Suggest what the results of the investigation show about the minimum
temperature required for photosynthesis in Elodea
...
(2)
...
...
...
...
(iii) Explain the meaning of the following statement
...
”
(2)
...
1 = 12 marks)
5
...
(Jan 2013)
(a) Explain why the light-independent stage cannot take place without the lightdependent stage
...
...
...
...
Enzymes control the rate of photosynthesis in Elodea
...
(4)
...
...
...
...
(Total for Question 5
...
...
...
...
...
...
...
...
...
...
(June 2013)
(b) The photosynthetic cells contain many chloroplasts
...
(3)
(a) Suggest why each of the following is important for the
production of
carbohydrates in the photosynthetic cells
...
(1)
A carbon fixation
B hydrolysis
C phosphorylation
D photolysis
(iii) Place a cross in the box next to the name of the enzyme
involved in reaction S
...
(4)
...
...
5
...
...
...
...
...
...
...
...
...
(Total for Question 2 = 13 marks)
2(a)(i)
1
...
idea of penetration of light ;
3
...
transport (in xylem) of water (to the leaves) /
eq ;
2
...
(water) for {light-dependent reaction /
photolysis / source of hydrogen (ions)};
OR
idea of (transporting sugar) to make more
room for more carbohydrate synthesis ;
Accept H2O but ignore incorrect formula
Accept phosphates but ignore mineral
ions
Not glucose or any other name sugars
Accept reducing power, NADPH
Accept (phosphates) for ATP synthesis
(2)
2
...
I
...
CC
2(b)(iv)
1
...
(which is) β glucose ;
3
...
between C1 and C4 / these bonds are 1-4
(glycosidic bonds) ;
5
...
reference to {straight / unbranched} (chains of
glucose) ;
7
...
The diagram below shows a chloroplast
...
(1)
(b) Give one other factor, not shown above, that would be required for this reaction to
occur in a chloroplast
...
(1)
(c) Describe the role of the electrons in the light dependent reaction of photosynthesis
...
...
(a) (i) Name the parts labelled A, B, C and D
...
B
...
C
...
(2)
(ii) State the part of the chloroplast, shown on the diagram, where oxygen is produced
...
(4)
(d) Describe and explain how the products of the light dependent reaction are involved in
the production of glyceraldehyde-3-phosphate (GALP)
...
(1)
(iii) Explain how oxygen is produced in chloroplasts during photosynthesis
...
...
...
High
concentrations of oxygen, within a chloroplast, can reduce the rate of photosynthesis
...
...
...
...
...
(4)
(e) GALP does not accumulate in a chloroplast during photosynthesis
...
...
...
The diagram below summarises the light dependent reactions of photosynthesis
...
(3)
(c) Suggest two environmental conditions which could increase the rate of oxygen
production by plants
...
(a) Give the precise location within a chloroplast where this sequence of reactions
occurs
...
(2)(Total 11)
7
...
water hydrogen ions + oxygen gas + electrons
(a) Name the reaction shown
...
(2)
(b) Give the names of product A and product B
...
Product B
...
...
Describe and explain the likely effect of atrazine on the production of carbohydrate
in a chloroplast
...
...
...
...
The graph below shows changes in the amount of light given off as fluorescence by
the leaf
...
...
(4)
(e) Atrazine can be used as a weedkiller
...
...
...
Suggest how crop plants unaffected by atrazine could be used to increase
crop yields
...
...
(2)(Total 13)
9
...
Any excited electrons that are not taken up by
electron carriers follow pathway A and release energy as light in a process called
fluorescence
...
(Snab Jan 09)
(i) Suggest an explanation for the increase in fluorescence
...
...
(2)
(ii) Suggest a reason for the fall in fluorescence
...
(1)
(d) Explain why an inhibitor of carbon dioxide fixation would lead to an increase in
fluorescence
...
...
...
(4) (Total 12)
10
...
(Snab Jan 10)
(a) Name the molecules X and Y shown on the diagram
...
Y
...
(a) Name the structures A and B
...
B
...
You should answer this question in continuous prose
...
...
(i) RuBP (Ribulose bisphosphate)
...
...
...
...
...
(6)
(c) Name one region of the chloroplast in which all three of these molecules are found
...
...
(1)(Total 9)
12
...
(Samp 07)
11
...
(Samp 04)
(a) (i) Explain how the pair of electrons move from chlorophyll to the electron carrier
system
...
Complete the table below by writing in the
appropriate letter and the name of each structure
...
...
(2)
(ii) Explain how electrons lost from chlorophyll are replaced
...
...
2H2O 4H+ + 4e– + O2
(i) Explain what happens to the electrons released by photolysis
...
(2)
(iii) Explain how ATP is synthesised when electrons pass between electron carriers B
and C
...
...
...
(2)
(ii) The electrons are later involved in the reduction of NADP
...
...
b Explain how substance Y is converted to GALP
...
...
...
(3)
(c) The rate at which plants produce carbohydrate by photosynthesis is known as gross
primary productivity
...
GPP + R = NPP
GPP + NPP = R
GPP = NPP + R
GPP = NPP – R
(1)
(d) The table below shows the net primary productivity in four different ecosystems
...
...
GALP is converted to a phosphorylated 6-carbon sugar which in turn can be
converted to a number of products such as sucrose and glucose
...
Describe how phloem tissue is adapted for this function
...
...
...
(i) It is estimated that 85% of the energy available to primary consumers will not be
available to secondary consumers
...
Show your working
...
kJ m–2 year–1
(2)
(ii) Suggest two reasons for the differences in the net primary productivity as the
distance from the equator increases
...
...
(2) (Total 13)
13
...
(EdTB)
...
14
...
(a) Explain the term limiting factor with reference to photosynthesis
...
………………………………………
………………………………………………
...
……………………………………… (2)
(b) An investigation into the effect of light intensity and carbon dioxide concentration on
photosynthesis was carried out using pond weed
...
The light
was provided by a lamp
...
The graph below shows how the rate of oxygen production of the pond weed changed
with light intensity when immersed in two different concentrations of sodium
hydrogencarbonate
...
(2)
X…………………………………………
Y……………………………
10
0
...
5 mol dm –3 sodium
hydrogencarbonate
0
...
6
/ cm 3 min –1
………………………………………………
...
………………………………………
0
...
………………………………………
0
...
1 mol dm –3 sodium
hydrogencarbonate
0
...
…………………………… (3)(Total 14 marks)
15
...
Explain why temperature can be a limiting factor in photosynthesis
...
2
0
...
………………………………………
0
0
50
100
150
200
250
300
350
400
Light intensity / arbitrary units
(i) Explain the shape of the graph between a light intensity of 0 and 400 arbitrary units in
the sodium hydrogencarbonate concentration of 0
...
………………………………………………
...
……………………………………… (2)
(b)
The diagram below shows the structure of a chloroplast
...
……
………………………………………………
...
……
………………………………………………
...
……
………………………………………………
...
………………………………………………
...
A ……………………………………………
...
………………………………………
C ……………………………………………
...
5 carbon compound + X
………………………………………………
...
……
Regeneration
………………………………………………
...
…… (3)
(iii) A number of precautions would need to be taken while carrying out this investigation
in order to obtain reliable data
...
Y
NADPH + H +
ATP
Triose phosphate
Glucose phosphate
………………………………………………
...
………………………………………………
...
… Y ………………………………… (2)
………………………………………………
...
Describe the process of photolysis and explain its role
...
…
...
11
………………………………………………
...
………………………………………………
...
………………………………………………
...
………………………………………
...
………………………………………………
...
………………………………………………
...
Simazine is a herbicide that kills plants by disrupting the flow of electrons in the
membranes of chloroplasts
...
Two
samples of plants were grown under the same controlled conditions
...
Both samples were supplied
with radioactive carbon dioxide (14CO2) in a well lit, sealed chamber for an hour
...
The mass of
radioactive carbon fixed in the plants was measured
...
...
(1)
(b) Explain why the plants were killed immediately after they were removed from the
chamber
...
(1)
(c) The results of the experiment are given in the table below
...
6
1
...
...
(2)
(d) An investigation of photosynthesis in cells taken from a green alga was carried out
...
The quantities of GP and RuBP in these cell samples were measured
...
After 3 minutes, the concentration of carbon dioxide was decreased to
0
...
The graph below shows the results of this investigation
...
003% carbon dioxide
Quantities
of RuBP
and GP
/ arbitrary
units
RuBP
GP
0
1
2
3
4
5
6
Time / minutes
(i) Describe the effects of the decrease in the concentration of carbon dioxide on the
quantities of GP and RuBP
...
...
...
...
(2)
(ii) Suggest explanations for the effects you have described in part (i)
...
(5)(Total 7 marks)
17
...
They are synthesised from glycerate 3-phosphate (GP)
...
...
(1)
18
...
...
(2)(Total 9 marks)
12
Scale in mm
...
(2)(Total 12 marks)
Light
Capillary tube
19
...
Syringe
CO 2
Gas bubbles
RuBP
Aquatic plant in
perforated tube
FBPase
Test tube filled
with water
Glucose
PGA
PGAL
(a) Explain what is meant by the term limiting factor
...
...
(2)
(b) State two environmental conditions, other than light intensity, which would need to
be controlled
...
...
...
...
(4)
(c) The aquatic plant was allowed to carry out photosynthesis for 10 minutes
...
Sucrose
(a) Some stages of the Calvin cycle require energy from ATP
...
...
...
...
(5)
FBPase is an enzyme involved in one step of the pathway used to re-form the CO2
acceptor molecule RuBP
...
The graph below shows the effect of this treatment on the sucrose
content of the leaves of treated and untreated plants
...
...
200
% of normal
sucrose
content
150
100
50
...
0
Untreated Treated
plants
plants
(b) Describe the effect of reduced FBPase activity on the sucrose content of leaves
...
(4)
(d) Describe how you could modify this apparatus to determine the effect of different
wavelengths of light on photosynthesis
...
...
...
...
...
...
...
(a) In the space below, draw a diagram of a chloroplast showing the main features of
this organelle
...
Rate of
photosynthesis
/ arbitrary units
blue light
red light
(a) Using the information in the two graphs, explain the relationship between the
absorption and action spectra for this flowering plant
...
...
...
...
...
...
...
...
...
...
...
...
(2)(Total 10 marks)
21
...
...
...
...
a
...
1
...
(made of) membranes ;3
...
contain {pigment / chlorophyll} / eq ;5
...
i
...
(62
...
38
...
ii
...
ref to different lighting has little effect / little variation in percentage grain yields ;
2
...
which is (probably) {not significant/ insignificant} ;
4
...
the best yield is metal halide / eq ;
iii
...
crops can be grown {out of season / all year round} / eq ;
2
...
idea of less physical damage from {weather / animals / eq} ;
4
...
ref to control of other named factor, eg CO2,
temperature, humidity, water supply ;
2
...
1
...
reference
...
idea of {not hitting the {chloroplast / chlorophyll}} / it is transmitted ;
4
...
g
...
photosynthesis so more light can be used ;
b
...
{joules / energy} per {square metre / metre squared/(unit) area} per {year / unit time} ;
b
...
Award 2 marks for correct answer (84
...
84)
1
...
4 – 3
...
7) ;
2
...
4 ;[consequential errors apply]
iii
...
(QWC – Spelling of technical terms (shown in italics)
1
...
in {granum / grana} ;
3
...
electrons released from {chlorophyll/photosystem / eq} / eq ;
5
...
reference to series of {redox / oxidation & reduction / eq} reactions ;
7
...
reference to {synthesise ATP from ADP +P /phosphorylate ADP} ;
9
...
reference to ATP {synthetase / synthase /ase} ;
11
...
idea of electrons from {photolysis / eq} used to replace those lost ;
13
...
a
...
i
...
idea of carbon fixation produces {GP / eq};
2
...
{faster / eq} C-fixation means faster{sugar / starch / eq} production / eq ;
4
...
reference to increased GPP (of crop) ;
b
...
1
...
therefore this effects number of {collisions / enzyme-substrate complex} ;
b
...
1
...
idea that (in Central Europe) {temperatures never reach 25oC / data
for 25 oC is irrelevant} / 14oC is {within the range / close to the average temperature};
3
...
25 / 15
...
A has highest rates of CO2 fixation at 14oC / eq ;
5
...
{B / C / D /E / F / others} would have relatively low {growth / yield / eq} at 14oC/ eq ;
4
...
i
...
drawing mark - recognisable {granum / grana} with clear stacks (of thylakoids /
eq) shown /eq;
2
...
yes,no- no,yes
iii
...
reference to energy from light ;2
...
of water ;
b
...
Or
b
...
general points:
1
...
idea of top of the shore is shallower water where most wavelengths are available /
lower shore is deeper water where only green (and blue)available ;
3
...
high(est) rates in {red / blue} light / eq / {very low / lowest} in green light ;
5
...
high(est) rate in green light / eq ;
7
...
a
...
ACCEPT any mark point from a clearly annotated diagram
1
...
reference to (a granum is) a stack of {thylakoids / membranes} OR grana are
connected by lamellae ;
3
...
reference to (membranes contain) {ATPase / ATPase channel} ;
5
...
1
...
reference to formation of {glucose / hexose/ 6C sugar} (from GALP) ;
3
...
idea that cellulose consists of {ß-glucose / beta glucose } ;
5
...
reference to 1-4 (bonds) ;
7
...
idea that cellulose is a long chain molecule e
...
polysaccharide, polymer ;
9
...
1(a) D - stroma; (1)
(b)(i) 1
...
reference no damage
to {plant / leaf / other cells} (during sampling) / eq ; 3
...
idea of {RuBP / GP /
15
products / eq} cannot pass into {other cells / rest of plant} ; 5
...
idea of controlling the {mass / number/surface area} of cells ; 7
...
light is needed for light-dependent reaction ; 2
...
idea that {the effect of carbon dioxide concentration can be seen /
carbon dioxide (concentration) is (only) limiting factor / eq } ; 4
...
{ATP / NADPH / light-dependent products /
eq} required for {light-independent reactions / Calvin cycle / carbon dioxide fixation} ; (3)
(b)(iii) 1
...
ref to
(RuBP and GP in) Calvin cycle ;
RuBP 3
...
rises because being regenerated / eq ; 5
...
idea that RuBP level remains constant once (new) equilibrium
reached ; GP 7
...
drops because less {carbon dioxide available to convert into GP) / less carbon fixation
/ eq} ; 9
...
credit correct manipulation of figures for a description of either RuBP or GP ; (6)
5
...
idea that products of lightdependent stage are {needed for / used in / eq} {lightindependent stage / Calvin cycle} ; 2
...
reference to use of {reduced NADP / eq} for {reduction
/ eq} of {carbon dioxide / GP / eq} ; 4
...
Accept source of hydrogen ions for GALP Ignore ref to ATP (3)
(b)(i) D volume of oxygen produced ; (1)
(b)(ii) 1
...
idea of no photosynthesis at 0oC but photosynthesis is taking place
at 10 oC ; 3
...
idea that at 0 oC water is frozen ; 3
...
reference to abiotic factors {are non-living / non-biological / do not involve
organisms / eq} ; 2
...
Ignore controlled
(2)(b)(iv) Supporting conclusion: 1
...
rate increases (up to 30 oC) because more {enzyme-substrate
complexes / collisions between enzymes and substrates} / eq ; 3
...
idea that other
factors could be affecting photosynthesis ; 5
...
idea of {correlation / not causation} ; 1
...
(a) (i) A stroma B starch (grain) / lipid droplet C thylakoid (membrane) / chlorophyll
D granum (2) for all correct (1) for 2 or 3 correct 2 marks
(ii) C / thylakoid / granum / D ; 1 mark
(iii) photolysis/splitting water using light energy ; release of electrons to chlorophyll ;
releases hydrogen ions ; oxygen released ; OH source of oxygen ; 3 marks
(b) reduced production (of carbohydrate) ; less carbon dioxide fixed ;ref RuBP ;
ref Calvin cycle / eq ; less carbon available for reduction to carbohydrate ;
ref to enzyme / RuBPcarboxylase ; 3 marks
(c) high light intensity ; ref
...
passed to chlorophyll / photosystem / replace electrons lost by chlorophyll / eq ;
2
...
ATP production ; 4
...
reference to electron carriers / electron transport chain ; 6
...
GP ; 2
...
using H from reduced NADP ;4
...
10/12 GALP /eq ;2
...
(rest used to form) glucose ;4
...
(a) 1
...
membrane ; (2)
3(b) A ATP; B reduced NADP / eq; (2)
3(c) photolysis; (1)
3(d) 1
...
less reduced NADP ;
3
...
less ATP (to supply energy) ;
5
...
competition ; 2
...
for carbon dioxide; 4
...
for water / ions ; 6
...
treat crop with atrazine ; 2
...
reference to reduced competition ; 4
...
reference to selective breeding / genetic modification ; max (2)
9
...
provides {H / electrons / eq} ; 2
...
GP is (reduced)/ eq ; 4
...
during light-independent {stage / eq} / Calvin cycle / eq ; max (3)
2(c)(i) 1
...
carriers can not {accept / take up / eq} electrons ;
3
...
NADP stays reduced /NADPH not used / eq ;
2
...
because RuBP cannot take up CO2 / eq ;
4
...
(because NADPH not used) all electron carriers
reduced / path B blocked / eq ; 6
...
(a) A – thylakoid (membrane) ; B – granum / grana ; (2)
1(b)(i) 1
...
ref fixation of carbon dioxide ; 3
...
ref reduction (to GALP) ; 2
...
ref use of ATP ; (2)
1(b)(iii) 1
...
formation of glucose / other organic compounds /produce biomass / eq ;
3
...
(a) (i) (Gaining) light energy/chlorophyll excited/photoexcitation Results in {excited
electrons/electrons raised to a higher energy level} Electrons able to leave chlorophyll
molecule/oxidation of chlorophyll Get picked up by molecule A/must have somewhere to
go 2 marks
(ii) Photolysis/splitting using light energy Of water Hydroxide ions as source of
electrons/2OH- 2OH + 2e- Cyclic photophosphorylation 2 marks
(iii) As electrons move from carrier to carrier energy is released/eq
Oxidation — reduction reactions
(Energy used to) synthesise ATP from ADP + Pi
H+ moved into lumen of thylakoid using light energy
16
H+ diffuse out of thylakoid synthesising ATP 2 marks
(b) 1
...
(During the) light independent stage
3
...
Reference to {RuBP carboxylase/Rubisco} 5
...
Reference to {reduced NADP/NADPH+/NADPH2}
7
...
To {GALP/TP/PGAL/3C sugar/triose}
9
...
{GALP/eq} used to form glucose
11
...
a
...
i
...
{enter / used in} {Photosystem II / PSII}; 2
...
after {excitation by light / absorption of light};
4
...
ref to reduction of CO2;2
...
in Calvin cycle;4
...
leads to formation of carbohydrate; 6
...
less light available farther from equator;
2
...
{less water available / lower rainfall} farther from equator;
4
...
Accept converse statements
...
a X Ribulose bisphosphate / RuBP 5 (carbon atoms)
Y {PGA / GP / eq} 3 (carbon atoms) [1 mark for each two correct] (2)
b Y is reduced; Using ATP and reduced NAD; (2)
c 1 Reference to sieve tubes (cells) and companion cells;
2 Sieve tube cell has {perforated end walls / sieve plates};
3 To allow passage of materials / eq;
4 Sieve tube cell has no nucleus / reference to nucleus present in companion cell;
5 No vacuole / few cell organelles / organelles pushed to the sides;
6 To provide more space for translocation;
7 Companion cell has {dense cytoplasm / many mitochondria / eq}
for {metabolic activity / energy};
8 Plasmodesmata connecting sieve tube cell with companion cell;
9 For exchange of materials / eq; 10 Transfer cells;
11 To load the sieve tube cells; (6) [Total 10 marks]
14
...
Increase in rate from 0 to 300 / 350 (light intensity) ;
2
...
Light is the limiting factor / eq ; [accept converse]
4
...
Another factor has become limiting ;
6
...
(Provides) carbon dioxide ;
2
...
Reference to comparative figures for rates / approx
...
For both concentrations rate starts to levels off at 300 / 350 light intensity / lower
concentration levels off above 250 compared with 300 ;
5
...
Splitting water in (presence of) light ;
2
...
Electrons replace the electrons lost from PS11 / P680 / chlorophyll ;
4
...
NADPH / eq used, in light-independent reaction / Calvin cycle / to reduce carbon
dioxide ; 3[14]
15
...
Sucrose ;
2
...
Active process / requires {energy / ATP} ;4
...
Reference to {reduction in cell organelles / sieve plates / perforated end walls} ;
6
...
Mass flow ;
17
8
...
From {leaves / eq} to {growing regions / storage organs} / reference to source to sink ;
10
...
(a) Light {intensity / wavelength} / photoperiod / carbon dioxide concentration / {soil
/ eq} / {watering / humidity} / temperature / {age / size / mass / eq} of plant;
1
[Reject amount]
(b) Prevent { reactions / respiration / photosynthesis / carbon fixing / uptake
1
of carbon dioxide} / eq;
(c) 1
...
ATP produced in {light dependent reactions / photosystems /chloroplast membranes /
thylakoids};
3
...
RuBP regeneration requires ATP / cannot regenerate RUBP;
5
...
Production of carbohydrate requires ATP / less carbohydrate produced;
7
...
Conversion to PGAL requires energy from ATP / reduced NADP;
9
...
(a) Stroma of chloroplast / stroma
1
+
(b) NADPH / reduced NADP / NADPH2 / NADPH + H / NADPH + H; ATP;
2
(c) Idea of carbon dioxide fixation / carbon dioxide acceptor;
To form 6C {compound / intermediate / molecule} / to form {2 × 3C molecules / GP};2
(d) (i) RuBP increases and GP decreases;
Description of one curve (e
...
GP decreases and levels off, both quantities equal at 3
...
[RuBP rises because ] it is being regenerated / it accumulates / eq;
2
...
[GP falls because] less is being formed;
4
...
(a) 1
...
Increasing this factor increases the rate (of photosynthesis);
3
...
Temperature; Use water bath / description of heat filter / eq;
2
...
{Wavelength / colour} of light; Use same {light source / filter / gel};
4
...
{Equilibrate / eq} before timing;
2
...
Use syringe to move {oxygen / gas bubble} into capillary tube eq;
4
...
Correct reference to determining volume of oxygen / eq;
6
...
Reference to repeats to give {mean /reliable} results / eq;
4
(d) 1
...
Reference to appropriate qualification e
...
filters placed in correct position / keeping
light intensity the same / all other factors the same
2 [12]
19
...
Light harvested / eq; 2
...
Reference to {accessory / eq} pigments;
4
...
Reference to carriers / electron acceptors / electron transport chain;
6
...
Photophosphorylation;
8
...
Less PGAL converted to RuBP / less RuBP reformed;
2
...
Enzymes for sucrose more active than for RuBP production; 2
(d) 1
...
Sweeter crop / better quality crop;
3
...
Increased profit;
2[11]
20
...
shape and quality of diagram;
ACCEPT round / oval clear diagram with a smooth, clear, complete outline
...
double membrane i
...
has two lines clearly not cristae;
3
...
correctly labelled position of light dependent and independent reactions;
4
(b) 1
...
(photosystems) {emit /eq} electrons;
3
...
ATP generated / eq; 5
...
using {H / eq} from {photolysis /eq}; 7
...
oxygen {diffuses out (of leaf / photosynthetic tissue) / used in respiration};
2
...
(a) 1
...
action spectrum shows activity at different wavelengths / eq;
3
...
indicates that pigments are involved in {photosynthesis / eq};
5
...
use of {chromatography paper / (silica) gel plates / eq};
2
...
left to run until solvent {reaches / near to} {top / other end} of {paper / plate};
4
...
reference to use of Rf values to identify pigments; max 4
(d)
1
...
less chlorophyll formed if magnesium deficient / eq;
3
Title: Biology Edexcel unit 4 photosynthesis
Description: past paper questions and answers
Description: past paper questions and answers