photosynthesis

Question 1

describe how the structure of the granum is adapted to its function

Answer 1

1 contain , (named) pigment (molecules) /
photosystems ;
2 contain ,
(named) electron carriers / ETC / ATP synth(et)ase ;
3 idea that has a large surface area (in a small volume)
for , light absorption /
light dependent reaction(s) /
light dependent stage /
electron transport ;

Question 2

with reference to the biochemistry of photosynthesis, explain why the theoretical rate of photosynthesis is not achieved at higher light intensities

Answer 2

1 at high light intensity
other (named) factor becomes a limiting factor ;
2 idea that temperature becomes limiting as ,
Calvin cycle / light independent reaction ,
involves enzymes /
relies on kinetic energy of molecules ;
3 idea that CO2 (concentration) becomes limiting as it is
required for ,
Calvin cycle / light independent reaction /
formation of (named) Calvin cycle compound /
reaction with RuBP / fixation by Rubisco ;

Question 3

suggest one way in which the structure of a leaf from a plant adated to shade differs from a plant adapted to light

Answer 3

shade leaf will have
1 large(r) / more , chloroplast(s) / (palisade) mesophyll ;
2 more , grana / thylakoids (in chloroplast) ;
3 large(r) surface area (of leaves)

Question 4

outline the ways in which heterotrophic organisms are dependent on plants

Answer 4

1 animals / heterotrophs (need to) obtain organic material from plants / autotrophs ;

2 (plants / autotrophs) produce organic molecules during photosynthesis / Calvin cycle /

3 (plants / autotrophs) produce oxygen during , 
photosynthesis / photolysis / 
light dependent stage; 
4 glucose / carbohydrate / oxygen , 
(produced in photosynthesis) 
are used in respiration by , 
animals / heterotrophs ;

Question 5

name a primary photosynthetic pigment

Answer 5

chlorophyll A

Question 6

name an accessory pigment

Answer 6

chlorophyll b, xanthophyll carotenoid

Question 7

state the advantage of a plant containing a range of accessory pigments in photosystems

Answer 7

able to absorb
a range of different
(light) wavelengths

Question 8

Name the compound that is synthesised in the light-dependent stage as a result of the generation of an electrical and pH gradient across the thylakoid membrane.

Answer 8

ATP

Question 9

Identify the enzyme that catalyses the fixation of carbon dioxide.

Answer 9

rubisco / RuBP carboxylase

Question 10

Identify the first stable product of carbon dioxide fixation.

Answer 10

GP / glycerate(3-)phosphate

Question 11

Identify the compound that is regenerated in the Calvin cycle so that more carbon dioxide can be fixed.

Answer 11

RuBP / ribulose bisphosphate

Question 12

Name two different polysaccharides that can be synthesised from the end products of the light-independent stage of photosynthesis.

Answer 12

starch / amylose / amylopectin
and
cellulose ;

Question 13

a product of the light-dependent reaction that is not used in the light-independent reaction.

Answer 13

oxygen

Question 14

a 5-carbon compound

Answer 14

ribulose bisphosphate / RuBP

Question 15

a compound that can be made from TP but is not part of the Calvin cycle.

Answer 15

amino acid

Question 16

a 3-carbon compound

Answer 16

glycerate-3-phosphate / GP / triose phosphate / TP ;

Question 17

a product of the light-dependent reaction that is used in the light-independent reaction.

Answer 17

ATP / reduced NADP ;

Question 18

Suggest what this raw material might be used for in the chloroplast.

Answer 18

for membrane formation
or
phospholipid / cholesterol / glycolipid , for membrane ;
fatty acid / (named) pigment , synthesis

Question 19

describe how light is harvested in the chloroplast membranes.

Answer 19

1 (primary & accessory) pigments are in photosystem
2 photon / light energy , absorbed by pigments
3 electron , excited / moves to higher energy level
4 (energy / photon) passed from one pigment
to another ;
5 (energy / photon) passed to reaction centre with chlorophyll a / P680 / P700 /
PSI / PSII /
range of accessory pigments allow range of wavelengths to be absorbed

Question 20

Triazine herbicide acts on the weeds by binding to a specific protein associated with photosystem II, blocking the movement of electrons between electron carriers.
Explain the effect that the herbicide binding to this protein will have on photosynthesis.

Answer 20

1 prevents non-cyclic photophosphorylation ;
2 no electron(s) available to form 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 ;

Question 21

Plants treated with triazine herbicide can, when illuminated under experimental conditions, be seen to fluoresce (emit light) and give off small quantities of heat.
Suggest how this experimental finding could be explained.

Answer 21

idea that energy given off from ,
high energy / excited , electron
(emitted by , chlorophyll / reaction centre) ;

Question 22

Discuss why measuring carbon dioxide uptake may or may not give a better indication of photosynthetic activity than measuring oxygen production.

Answer 22

1 oxygen only produced in one (named) stage of
photosynthesis ;
2 oxygen produced might be used for respiration ;
3 carbon dioxide
CO2 only used in one (named) stage of photosynthesis ;
4 CO2 produced during respiration might be used for photosynthesis /
light independent reaction /
Calvin cycle ;
O2 / CO2 / both , could be an underestimate

Question 23

Name the process that produces carbon dioxide in the plant.

Answer 23

(aerobic / anaerobic) respiration ;

Question 24

Name the products of the light-dependent stage of photosynthesis.

Answer 24

reduced NADP / NADPH / NADPH2 / NADPH+ ;
ATP ;
oxygen ;

Question 25

Paraquat is a weedkiller. It binds with electrons in photosystem I.
Suggest how paraquat results in the death of a plant.

Answer 25

1 prevents photophosphorylation ;
2 cyclic and non-cyclic ;
3 no / less , ATP / reduced NADP , for ,
light-independent stage / Calvin cycle /
GP to TP ;
4 no (named) substrate made for respiration

Question 26

Suggest the role of DNA and ribosomes in a chloroplast

Answer 26

1 (DNA) coding for , gene(s) / protein / enzyme
or
(ribosome) protein / enzyme , synthesis ;
2 (enzymes for production of / proteins for)
chlorophyll synthesis / pigment synthesis /
photosystem ;
3 (protein for) electron , acceptor(s) / carrier(s) ;
4 ATP synth(et)ase ;
5 (enzyme / PSII) for , photolysis / splitting of water ;
6 (enzymes for)
Calvin cycle / light independent reaction ;

Question 27

The length of the gas bubble was measured (in mm).State what additional information would be required to calculate the volume of gas produced.

Answer 27

1 (internal) radius / diameter , of capillary tube ;
2 cross-sectional area (of capillary tube) ;
3 (use) π r2 h ;

Question 28

Suggest how the student supplied the aquatic plant with a source of carbon dioxide.

Answer 28

1 (sodium) hydrogen carbonate ;
2 bubble in , CO2 / exhaled air ;
3 dry ice ;

Question 29

Suggest why not all of the oxygen produced by the plant is collected

Answer 29

idea that some of the oxygen
1 would dissolve in the water ;
2 used in , respiration / oxidative phosphorylation ;
3 may escape the collection apparatus ;
4 trapped in , a bubble attached to / air spaces in ,
the leaf ;

Question 30

Suggest a reason for the presence of nitrogen in the gas collected.

Answer 30

1 (nitrogen) was present in the air (spaces) in the ,
leaf / plant ;
2 (nitrogen) leaves the plant with the oxygen ;
3 idea that (nitrogen) comes out of solution /
‘undissolved’ (as less soluble in warm water) ;

Question 31

Suggest why the presence of these pigments is an advantage to seaweeds that live in deeper water.

Answer 31

intensity
1 in deeper water there is , less / lower , light intensity ;
2 (these pigments) can absorb what (little) light there is ;
wavelength
3 not all wavelengths of light can penetrate
or
mainly shorter wavelengths can penetrate
or
(mostly) blue light (450 – 520 nm) penetrates ;
4 (these pigments) can absorb
wavelengths of light that can penetrate
(deeper water) ;

Question 32

Suggest and explain one benefit of the greater mean number of stomata per mm2 on the lower surfaces of the sun leaves.

Answer 32

benefit
allows entry of more CO2 ; 
explanation 
(CO2) for , light-independent reaction / Calvin cycle 
or 
light-dependent reaction is taking place quickly / 
reduced NADP building up / ATP building up 
or 
CO2 not as limiting (than when there are fewer stomata) 
or 
idea that increases access to air spaces
for distribution of CO2 ; 
OR 
benefit 
reduces transpiration ; 
explanation 
idea of stomata sheltered from , air currents / heat 
(when on lower surface) 
or 
idea that diffusion shells maintained ;

Question 33

Name the products of the light dependent stage that are used in the Calvin cycle.

Answer 33

ATP ;
reduced NADP / NADPH / NADP
H2 / NADPH + H+ ;

Question 34

Discuss the fate of triose phosphate (TP) in the Calvin cycle.

Answer 34

regenerates / produces , ribulose bisphosphate / RuBP ;
so cycle can continue / for (further) CO2 fixation /
to combine with CO2 ;
formation of (named) , sugar / glucose / hexose / sucrose /
starch / cellulose ;
formation of (named) ,
fat / triglyceride / lipid / fatty acids / glycerol /
amino acids / protein /
nucleic acids / nucleotides ;
10x TP for RuBP and 2x TP for production
or
most TP used to produce RuBP and the rest for production ;

Question 35

How can factors other than light conditions be controlled to increase the rate of photosynthesis and maximise production?In your answer you should explain why the rate of photosynthesis is affected by the controlled factors you have discussed.

Answer 35

photosynthesis / named stage,
is controlled by / needs / involves / uses ,
(named photosynthetic) enzymes ;
temperature can be,
increased by heater /
reduced by ventilation (or fan)
maintained by air conditioning (or other method) ;
increase CO2 concentration (in environment) by burning,
fuel / gas / paraffin ;
idea that increased / more / higher, CO2 (conc),
so CO2 no longer a limiting factor /
increases CO2 fixation / (or described)
increases Calvin cycle (or described) ;
idea that easier to control,
water supply / irrigation (to prevent wilting) / humidity /
minerals / fertiliser ;
idea that easier to control use of,
pesticides / pest control / biological control ;