Download 4. Photosynthesis Booklet TN

SACKVILLE SCIENCE DEPARTMENT
A2 BIOLOGY
Photosynthesis Booklet Teachers Notes/Markscheme
Structure and role of chloroplasts
1. (a)
W
(chloroplast outer) membrane/envelope;
DO NOT CREDIT cell/plasma, membrane
DO NOT CREDIT inner membrane alone but
IGNORE if stated together with outer
X
granum/grana;
ACCEPT granal stack/thylakoid stack
Y
stroma;
DO NOT CREDIT stoma/matrix/cytoplasm
Z
thylakoid(s)/(intergranal) lamella(e);
Mark the first answer on each prompt line. If the answer is correct and an additional
answer is given that is incorrect or contradicts the correct answer then = 0 marks.
(b)
(1) (DNA) coding for, gene(s)/protein/enzyme or (ribosome) protein/enzyme, synthesis;
IGNORE ‘information’/ref to replication
DO NOT CREDIT making amino acids
(2) (enzymes for production of/proteins for) chlorophyll synthesis/pigment
synthesis/photosystem;
(3) (protein for) electron, acceptor(s)/carrier(s);
CREDIT named acceptor/carrier (e.g. NADP/cytochrome)
(4) ATP synth(et)ase;
(5) (enzyme/PSII) for, photolysis/splitting of water;
(6) (enzymes for) Calvin cycle/light independent reaction;
CREDIT Rubisco
DO NOT CREDIT any mps in context of respiration
2. autotroph
can make, organic molecule(s)/named organic molecule(s), from, inorganic
molecule(s)/carbon dioxide;
IGNORE ref to biological molecules
ACCEPT fixes carbon dioxide to produce (named) carbohydrates/protein/lipid
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heterotroph
relies on/needs to use/has to obtain/feeds on and digests, (named) organic molecules (that
have been made by another organism);
idea of need or taking in and breaking down is important
‘gets its organic molecules from another organism’ = 0 marks
‘has to get its organic molecules from another organism’ = 1 mark
Mark the first answer on each prompt line. If the answer is correct and an additional
answer is given that is incorrect or contradicts the correct answer then = 0 marks.
3. (a)
E
granum/grana;
IGNORE ref to stacks of, lamellae/thylakoids
F
stroma;
DO NOT CREDIT stoma/storma
Mark the first answer on each prompt line. If the answer is correct and an additional
answer is given that is incorrect or contradicts the correct answer then = 0 marks.
(b)
for membrane formation or phospholipid/cholesterol/glycolipid, for membrane;
fatty acid/(named) pigment, synthesis;
IGNORE ref to ATP production (as primarily generated by photophosphorylation in a
chloroplast)
ACCEPT ref to repair of membrane
ACCEPT ref to (chloroplast) envelope instead of membrane
DO NOT CREDIT ref to cell surface membrane (as this is not in the chloroplast)
Pigments and light absorption
1.
intensity
(1) In deeper water there is, less/lower, light intensity;
(2) (these pigments) can absorb what (little) light there is;
ACCEPT trap/harvest/capture
IGNORE use/collect
wavelength
(3) Not all wavelengths of light can penetrate or mainly shorter wavelengths can penetrate
or (mostly) blue light (450-529nm) penetrates;
idea of restricted range of wavelengths able to penetrate (rather than wavelengths are
different)
ACCEPT ‘higher frequency’ instead of ‘shorter wavelength’
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(4) (these pigments) can absorb wavelengths of light that can penetrate (deeper water);
ACCEPT trap/harvest/capture
IGNORE use/collect
2. (a) (i) control;
CREDIT a description e.g. comparison; to compare results with; to show that (wavelengths
of) light is producing the effect; to show the result produced without light; create baseline;
create set point; validity
IGNORE ‘fair test’
DO NOT CREDIT ‘control variable’/’controlled variable’
(b)
(1) discs, the same size/cut with same cutter, so same surface area;
ALLOW for same amount of pigment/chloroplast
(2) discs taken from same part of the leaf/leaves used from the same part of the plant so
same amount of, pigment/chloroplast;
(3) tubes same distance from light source so light intensity is the same;
(4) light bulb the same (wattage) each time so light intensity is the same;
(5) same thickness of filter so light intensity is the same;
(6) carry out in darkened room/only 1 light source in room/completely cover tube with
filter, so only light of desired wavelength enters;
(7) CO2 in excess/AW, so CO2 not limiting/enough CO2 for photosynthesis/enough CO2 for
Calvin cycle/enough CO2 for light dependent stage;
(8) same, volume/concentration/batch, of indicator so that colour changes are
comparable;
(9) heat, sink/shield, between light source and tube to reduce temperature changes;
(10) carry out at, same/constant, temperature as temperature affects enzyme,
activity/structure;
ALLOW for same amount of pigment/chloroplast
Enzyme ref must be qualified
(11) carry out, repeats/replicates, to, calculate mean/identify anomalies;
IGNORE ref to improving reliability
IGNORE how anomalies dealt with
DO NOT CREDIT preventing anomalies
(12) AVP (to include precaution and explanation);
CREDIT any reasonable precaution with a suitable explanation (even if explanation already
given) e.g. rinse test tubes with distilled water so starting pH is the same
(c) chlorophyll a;
ALLOW chlorophyll A/chlorophyll
IGNORE p680/p700/PSI/PSII
DO NOT CREDIT chlorophyll a and b
DO NOT CREDIT chlorophyll alone
Mark the first answer. If the answer is correct and an additional answer is given that is
incorrect or contradicts the correct answer then = 0 marks.
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(d)
(1) chlorophyll/pigments/leaf, reflect/does not absorb/absorbs little, green light/light of this
wavelength;
Needs to refer to green rather than other colours
(2) (green light) cannot be used in photosynthesis/no photosynthesis/little
photosynthesis/no light dependent reaction (or described)/little light dependent
reaction (or described) correct ref to action spectrum in green region;
Needs to refer to green rather than other colours
(3) little/no, photolysis/splitting of water;
CREDIT (some) photolysis with accessory pigments
(4) little/no, CO2, taken up/fixed (in light independent reaction);
(5) some CO2 produced during respiration;
(6) (slight) increase in CO2, increases acidity/decreases pH;
CREDIT increase in H+ decreasing pH for accessory pigments
(7) AVP;
e.g. accessory pigments absorb (some) green light
The biochemistry of photosynthesis
1.
Mark the first answer in each box. If the answer is correct and an additional answer is given
that is incorrect or contradicts the correct answer then = 0 marks.
ACCEPT lower case letters
DO NOT CREDIT ‘N and C’ instead of B, as they have been asked to use B
IGNORE ‘N and C’ if stated in addition to B in rows 1 and 2
ACCEPT B for this row
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A2 BIOLOGY
2.
(1) (primary and accessory) pigments, are in/form a(n), photosystem/complex/antenna
complex;
if pigments are named, state that chlorophyll a and at least 1 name accessory pigment are in
a photosystem
(2) photon/light energy, absorbed by pigment (molecule(s));
idea of absorption required in the context of this Q
IGNORE falls on/hits/strikes
(3) electron, excited/moves to a higher energy level/delocalised, and returned to pigment;
DO NOT CREDIT if this electron is passed to, electron acceptor/ETC
DO NOT CREDIT in context of chlorophyll a
(4) (energy/photon) passed from one pigment to another;
DO NOT CREDIT ref to electron being passed
(5) (energy/photon) passed to, reaction centre/chlorophyll a/P680/P700/PSI/PSII/primary
pigment;
DO NOT CREDIT ref to electron being passed
But apply ecf from mp 4
(6) range of/accessory, pigments allow range of wavelengths to be absorbed;
CREDIT ‘photon energy’ for ‘wavelengths’
IGNORE in context of P680 and P700
IGNORE ref to photophosphorylation, as irrelevant to Q
QWC – technical terms used appropriately and spelt correctly;
Use of three terms from: pigment, antenna complex, photon, reaction centre, chlorophyll
a/A, primary accessory wavelength(s)
3. (a) rubisco;
Mark the first answer. If the answer is correct and an additional answer is given that is
incorrect or contradicts the correct answer then = 0 marks.
(b) ATP/reduced NADP;
DO NOT CREDIT oxygen (as it is not used in the light independent reaction)
Mark the first answer. If the answer is correct and an additional answer is given that is
incorrect or contradicts the correct answer then = 0 marks.
(c) glycerate-3-phosphate/GP/triose phosphate/TP;
Mark the first answer. If the answer is correct and an additional answer is given that is
incorrect or contradicts the correct answer then = 0 marks.
(d) amino acid;
Mark the first answer. If the answer is correct and an additional answer is given that is
incorrect or contradicts the correct answer then = 0 marks.
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(e) ribulose bisphosphate/RuBP;
ACCEPT ribulose biphosphate
Mark the first answer. If the answer is correct and an additional answer is given that is
incorrect or contradicts the correct answer then = 0 marks.
(f) oxygen;
DO NOT CREDIT ATP/reduced NADP (as they are used in the light independent reaction)
Mark the first answer. If the answer is correct and an additional answer is given that is
incorrect or contradicts the correct answer then = 0 marks.
4. (a)
Credit in either order
ATP;
Reduced NADP/NADPH/NADPH2/NADPH + H+;
DO NOT CREDIT reduced NAD/NADH/NADH2/NADH + H+
DO NOT CREDIT oxygen/O2 (as not used in Calvin cycle)
Mark the first two answers. If either of the answers is correct and an additional answer (i.e.
3rd etc.) is given that is incorrect or contradicts the correct answer then -1 for each
additional incorrect answer.
e.g. ATP () and NADPH () and GP (-1) = 1
NADH () and ATP () and oxygen (-1) = 0
GP () and H2O () and ATP and NADPH = 0
ATP () and NADPH () and GP (-1) and H2O (-1) = 0
(b)
(1) regenerates/produces, ribulose bisphosphate/RuBP;
(2) so cycle can continue/for (further) CO2 fixation/to combine with CO2;
(3) formation of (named), sugar/glucose/hexose/sucrose/starch/cellulose;
IGNORE carbohydrate without qualification but
CREDIT suitably named carbohydrate
(4) formation of (named) fat/triglyceride/lipid/fatty acids/glycerol/amino
acids/protein/nucleic acids/nucleotides;
(5) 10 x TP for RuBP and 2 x TP for production or most TP used to produce RuBP and the rest
for production;
Needs to refer to both
CREDIT 5/6 regenerated and the rest for production
(c)
oxygen used and carbon dioxide, produced/excreted;
(only) occurs in the light/light (energy) required or uses, (same) photosynthetic
enzyme/Rubisco or involves Calvin cycle;
DO NOT CREDIT comments that categorically state ‘it is respiration’
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CREDIT ‘sun’ instead of ‘light’
IGNORE ref to light dependent stage [S and C x 2]
(d)
(1) reduces (rate of) photosynthesis/increases (rate of) photorespiration;
(2) less Rubisco available for CO2/more oxygen competing with CO2 for Rubisco/more O2
binding to Rubisco/O2 outcompetes CO2 for Rubisco;
ACCEPT oxygen blocks active site of Rubisco
CREDIT ‘enzyme’ instead of Rubisco
Needs to convey the idea that oxygen more successful/more oxygenase activity
Be careful not to credit RuBP
(3) less CO2, fixation/for Calvin cycle;
(4) CO2 given off;
(5) Less, glycerate 3-phosphate/GP/TP, produced;
IGNORE number before name unless used to indicate more or less (compare flow charts)
(6) Less RuBP, regenerated/formed;
[S and C x 3]
(e)
idea that oxygen, not a substrate for/cannot bind to/will not compete for, PEP carboxylase
or PEP carboxylase, is only specific to carbon dioxide;
ACCEPT PEP carboxylase cannot ‘fix’ oxygen
[S and C x 1]
Photosynthetic rate
1.
(1) photosynthesis/named stage, is controlled by/needs/involves/uses, (named photosynthetic)
enzymes;
Needs to be clear generalised statement – cannot be implied from a description of the effects
(2) temperature can be, increased by heater/reduced by ventilation (or fan) maintained by air
conditioning (or other method);
IGNORE ‘enzymes are affected by temperature’
Needs to indicate how factor is controlled
(3) increase CO2 concentration (in environment) by burning, fuel/gas/paraffin;
(4) idea that increased/more/higher, CO2 (conc), so CO2 no longer a limiting factor/increases
CO2 fixation/(or described) increases Calvin cycle (or described);
Needs to indicate how factor is controlled
CREDIT increase in CO2 by other reasonable methods
ALLOW ref to maximum rate for increase in rate
(5) idea that easier to control, water supply/irrigation (to prevent
wilting)/humidity/minerals/fertiliser;
Look for idea that factors can be more easily regulated in the greenhouse rather than outside
CREDIT use of hydroponics
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A2 BIOLOGY
(6) idea that easier to control use of, pesticides/pest control/biological control;
Look for idea that factors can be more easily regulated in the greenhouse rather than outside
(7) AVP;
e.g. gas/paraffin, heater supplies heat and CO2; prevents described damage of plants by, wind
chill/frost/wind/hail/etc; description/effect, of photorespiration
Question is asking for an increased rate of photosynthesis and maximum production
IGNORE LIGHT
2. (a) (i) 0.0017;;
Correct answer, given to 4 dp = 2 marks
If answer not shown on answer line, CREDIT correct answer written in the appropriate space
in the table.
If answer is incorrectly rounded or rounded to the wrong number of dp or written in
standard form (1.7 x 10-3) then award 1 working mark.
If answer is incorrect then award 1 working mark for seeing 1 ÷ 576 or 1 ÷ 242
(a) (ii)
(1) (internal) radius/diameter, of capillary tube;
ACCEPT radius/diameter, of bubble
ACCEPT width of tube
(2) cross-sectional area (of capillary tube);
ACCEPT cross-sectional area of bubble
(3) (use) πr2h;
(a) (iii)
(1) (sodium) hydrogencarbonate;
ACCEPT bicarbonate
DO NOT CREDIT carbonate
(2) bubble in, CO2/exhaled air;
(3) dry ice;
(b) (i)
idea that some of the oxygen
(1) would dissolve in the water;
IGNORE ‘oxygen is in the water’
(2) used in, respiration/oxidative phosphorylation;
IGNORE produces energy
(3) may escape the collection apparatus;
(4) trapped in, a bubble attached to/air spaces in, the leaf;
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(b) (ii)
(1) (nitrogen) was present in the air (spaces) in the, leaf/plant;
(2) (nitrogen) leaves the plant with the oxygen;
idea that (nitrogen) comes out of solution/’undissolved’ (as less soluble in warm water);
(b) (iii)
(1) higher than, expected/normal/in atmosphere;
(2) (plant is) respiring/produces CO2 during respiration;
IGNORE produces energy
(3) CO2, has been added to water/is present in excess;
(4) (CO2) comes out of solution/’undissolved’ (as less soluble in warm water);
(5) less/low(er), as some CO2 will dissolve in, water/solution;
DO NOT CREDIT if in context of lower than O2 and N2
(6) less/low(er), as CO2 used in photosynthesis;
DO NOT CREDIT if in context of lower than O2 and N2
3. (a)
oxygen
(1) oxygen only produced in one (named) stage of photosynthesis;
CREDIT for O2 ‘only measures the rate of the light dependent stage/photolysis’
(2) oxygen produced might be used for respiration;
carbon dioxide
(3) CO2 only used in one (named) stage of photosynthesis;
CREDIT for CO2 ‘only measures the rate of the Calvin cycle’
(4) CO2 produced during respiration might be used for, photosynthesis/light independent
reaction/Calvin cycle;
(5) O2/CO2/both, could be an underestimate or represents net production (O2) or represents
net use (CO2);
ACCEPT a description e.g. ‘measurement is less than expected because not al the oxygen
produced can be measured’ (but not if expressed in terms of experimental error – e.g.
dissolves in the water)
IGNORE refs to reliability/accuracy
(b) (i) light intensity;
Mark the first answer. If the answer is correct and an additional answer is given that is
incorrect or contradicts the correct answer then = 0 marks.
(b) (ii) carbon dioxide concentration/partial pressure of CO2/temperature;
DO NOT CREDIT ‘high’ or ‘low’, as these indicate situations rather than factors
AVP;
e.g. stomatal density; stomatal size; chlorophyll concentration; number of chloroplasts;
enzyme turnover rate;
IGNORE (temporary) changes in stomatal, opening/closing
IGNORE ref to water availability
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Mark the first answer. If the answer is correct and an additional answer is given that is
incorrect or contradicts the correct answer then = 0 marks.
(b) (iii) (aerobic/anaerobic) respiration;
ACCEPT Krebs cycle/link reaction/decarboxylation
DO NOT CREDIT photorespiration (as light intensity stated as being low)
Mark the first answer. If the answer is correct and an additional answer is given that is
incorrect or contradicts the correct answer then = 0 marks.
(b) (iv)
(1) at 0, respiration only/no photosynthesis;
between 0 and X
(2) idea that (rate of) respiration is greater than (rate of) photosynthesis;
DO NOT CREDIT no photosynthesis
at X
(3) idea that (rate of) respiration equals (rate of) photosynthesis/at compensation point;
after X
(4) idea that (rate of) photosynthesis is greater than (rate of) respiration;
IGNORE photorespiration throughout
CREDIT ‘Calvin cycle’ for ‘photosynthesis’ throughout
For mps 2, 3 and 4 must include clear ref to both respiration and photosynthesis
(c) (i)
reduced NADP/NADPH/NADPH2/NADPH+;
ATP;
oxygen;
ACCEPT O2 (to be consistent with the other answers to this question)
Mark the first 3 answers.
IGNORE numbers of molecules
(c) (ii)
(1) prevents photophosphorylation;
(2) cyclic and non-cyclic;
(3) no/less, ATP/reduced NADP, for, light-independent stage/Calvin cycle/GP to TP;
‘no ATP for photosynthesis’ is not quite enough
DO NOT CREDIT (oxidised) NADP
(4) no (named) substrate made for respiration;
substrate e.g. glucose/starch/carbohydrate/sucrose/sugars
IGNORE triose phosphate/food/nutrients
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4. (i) -864.3 (kg ha-1); -7.4 (%);
DO NOT CREDIT answer that is not given to 1 dp
DO NOT CREDIT correct numerical answer without minus sign
If no answers on the answer lines, then look in the appropriate boxes in the table for the
answers.
ALLOW ecf from value for kg ha-1
(ii) idea that the number of, plots/samples, was, too/very, small;
Just ref to a smaller number of plots is not quite enough
CREDIT idea that the number of plots was not large enough
IGNORE ref to the idea that the difference is very large
(iii)
(1) prevents non-cyclic photophosphorylation;
IGNORE ref to cyclic photophosphorylation
(2) no electron(s) available to form reduced NADP;
CREDIT red NADP/NADPH/NADPH + H+/NADPH2 for ‘reduced NADP’
(3) idea that ATP production by cyclic photophosphorylation is not prevented;
(4) no/less, ATP and no reduced NADP available for, Calvin cycle/light independent
reaction/conversion of GP to TP;
(iv)
idea that energy given off from, high energy/excited, electron (emitted by,
chlorophyll/reaction centre);