photosynthesis

Question 1

Where does the light dependent stage occur (1)

Answer 1

grana/ thylakoid

Question 2

Where does light independent stage occur (1)

Answer 2

stroma

Question 3

Plants take up minerals from the soil They are combined with products from light independent stage to produce other molecules needed by the plant
Give three example of minerals taken up from the soil and sate what molecules are produced when each example combines with the products of the light independent stage (3)

Answer 3

• synthesis of amino acids/proteins using a nitrogen source
• synthesis of phospholipids using phosphate
• synthesis of chlorophyll using magnesium
• synthesis of nucleotides with nitrogen and phosphate source

Question 4

Explain how carbon dioxide is used in the production of glycerate-3-phosphate (2)

Answer 4

• ribulose bisphosphate and carbon dioxide linked together / carbon dioxide is fixed with RuBP
• RuBP carboxylase/RUBISCO is the enzyme that catalyses the reaction
• unstable 6c compound initially formed/split into two 3C

Question 5

Describ how glycerate-3-phosphate is converted to triose phosphate (3)

Answer 5

• glyverate 3 phosphate reduced
• using reduced NADP
• ATP also required to supply energy /glycerat-3-phosphate is phosphorylated
• reduced NADP/ATP from light dependent reactions

Question 6

State why only some of the triose phosphate produced by calvin cycle can be used to produce hexose phosphate (1)

Answer 6

some triose phosphate needed to regenerate RUBP

Question 7

Suggest how many time the calvin cycle must occur to produce one molecule of glucose (1)

Answer 7

six times

Question 8

Diuron is a weed-killer which is a very specific and sensitive inhibitor of photosynthesis. It blocks the
electron carrier binding site on photosystem II. This stops the electron flow from where it is generated, in
photosystem II, to the electron carrier. This reduces the ability of the plant to convert light energy into
chemical energy.
Diuron only blocks electron flow from photosystem II. It has no effect on photosystem I or other reactions
in photosynthesis, such as light absorption or carbon fixation in the Calvin cycle.
(a) Explain the effects of Diuron on non-cyclic photophosphorylation and why cyclic photophosphorylation
is not affected. (4)

Answer 8

• stops electrons for PSII being moved to PSI
• so blocking reducton of NADP to NADPH
• cyclic photophosphorylation only involved PSI
• is not stopped as electrons pass from PSI and return to PSI
• and the carrier involved in this is not affected

Question 9

Diuron is a weed-killer which is a very specific and sensitive inhibitor of photosynthesis. It blocks the
electron carrier binding site on photosystem II. This stops the electron flow from where it is generated, in
photosystem II, to the electron carrier. This reduces the ability of the plant to convert light energy into
chemical energy.
Diuron only blocks electron flow from photosystem II. It has no effect on photosystem I or other reactions
in photosynthesis, such as light absorption or carbon fixation in the Calvin cycle.
(b) Suggest why a plant would die when the weedkiller Diuron is sprayed onto it. (3)

Answer 9

• plant cannot regenerate NADPH so calcin cycle cannot work
• no hexose sugar will be formed
• for respiration

Question 10

Stae precicsley where chlorophull a is found in photosynthetic cell (2)

Answer 10

• reaction centre/antenna complex
• in photosystem
• in the thylakoid membrane

Question 11

Explain the advantage of plants having more than one pigment in their leaves (2)

Answer 11

• light/photons absorbed over a greater range of /more wavelengths
• more light/photons absorbed means more products from light dependent stage
• greater rate of photosynthesis/photosynthesis is more efficient

Question 12

Use your know,edge of photsynthesis to explain the role of these pigments in the production of ATP (3)

Answer 12

• light absorbed by pigments in photosystems
• excistes electrons to a higher energy level
• electrons emitted from reactio centre
• used to power proton pumps/generate electrochemical gradient
• movement of protons through stalked particle/ATP synthease

Question 13

Describe the function of chlorophyll a (1)

Answer 13

absorbs light energy

Question 14

Why do most leaves charicateristically have green colour (1)

Answer 14

all wavelenghts except green are absorbed/green is reflected or transmitted

Question 15

Describe the relationship between the absorption spectrum and the action pectrum and explain what this relationship tells us about light absorption and photosynthesis (2)

Answer 15

• since they follow a similar trend/ patter/shape
• suggests that the pigments/wavelengths responsible or used in light absorption are used in photsynthesis

Question 16

State exactly where in the chloroplast you would expect to find photosystems (1)

Answer 16

thylakoid membrane/granal membrane/intergranal membrane

Question 17

Name two processes which increase carbon dioxide levels (1)

Answer 17

• respiration
• combustion

Question 18

State which organelle in a plant cell is responsible for photosynthesis (1)

Answer 18

• chloroplast

Question 19

State precisley how the process of photsynthei reduces the carbon dioxide levels (2)

Answer 19

• light independent
• calcin cylcle
• RUBP
• rubisco

Question 20

Suggest why the folloing process are required for cellular repspiration to continue
light independent stage of photsynthesis (1)

Answer 20

• produces carbohydrate/glucose/respiratory substrate

Question 21

Suggest why the folloing process are required for cellular repspiration to continue
light dependent stage of photsynthesis (1)

Answer 21

produces oxygen

Question 22

Glycine is an amino acid which chemical element would have been needed in the mineral solution in order for algae to have made this compound (1)

Answer 22

• nitrogen

Question 23

state two products of the light dependent stage of photosynthesis required in the calvin cycle (2)

Answer 23

• ATP
• NADPH

Question 24

State one possible fate of hexose sugars produced (1)

Answer 24

• energy source/cellulose/lipids/food store/amino acids/proteins/pentose sugar/disaccharide

Question 25

Explain the role of photosystems in light dependent stage of photosynthesis (3)

Answer 25

• absorb light energy/photons
• act as transducer/ transferring light energy to high enrgy electrons
• which can be used to power proton pumps/synthesis ATP/syntehsis reduced NADP/electrons passed down electron transport chain

Question 26

Following the synthesis of carbohydrate a number of inorganic ions are needed to syntheis other biological molecules
state three different biological molecules and the inorganic ions required to synthesis them (3)

Answer 26

• amino acids/proteins - nitrates
• phospholipids - phosphates
• nucleotide - nitraes and phosphates
• chlorophyll -magnesium ions (nitrates)

Question 27

herbiciced inhibit photsynthesis in many ways
one group of herbicides block electron transport so chlorophyll contrinues to absorb light energy but cannot pass energy on
light energy not used in electron emmission damages chlorophyll leading to chlorosis
dessication occurs because of formation fo oxygen free radicals highly destructive to cell embranes
How does blocking electron transport from phosystems with herbicidee could lead to death of plant (4)

Answer 27

• destruction of chlorophull - no PS/unable to absrob light energy
• no /less NADH/ATP fro calvin cycle
• no/ less carbohydrate synthesied for syntheis of biological molecules/respiration
• no/less respiration there no /less ATP for cell division/protein synthesis/active transport
• destruction of cell membranes - kills/dries out cell

Question 28

Apart from chlorophyll a name three other pigments you would exprrect to be present in a photsystem (2)

Answer 28

• chlorophyll b
• carotene
• xanthrophyll

Question 29

State precisley where a photosystem would be found in plant cell (1)

Answer 29

thylakoid membrane in a chloroplast

Question 30

An experiment was carried out to investigate the effect of leaf colour on the rate of photosynthesis laves placed in water naturally float but if small discs of leaes are punched out of leaves are in discs replaced by hydrogen carbon solution they will sink
the time for 15 light green leaf discs float to top of solution when illuminated from below can be determine and gives an estimate of rate of photsunthesis repeated for dark green leaf discs
Explain what caused discs to rise in the solution (2)

Answer 30

• oxygen produced from photosynthesis/photolysis of water
• oxygen fills airspaces in the lead so the lead is less dense/lighter/more buoynat so rises

Question 31

An experiment was carried out to investigate the effect of leaf colour on the rate of photosynthesis laves placed in water naturally float but if small discs of leaes are punched out of leaves are in discs replaced by hydrogen carbon solution they will sink
the time for 15 light green leaf discs float to top of solution when illuminated from below can be determine and gives an estimate of rate of photsunthesis repeated for dark green leaf discs
Explain why the darker green leaf discs rose faster than the lighter green discs (4)

Answer 31

• darker leave rise more quickly as they have more chloroplasts/chlorophyll/pigment in palisade mesophyll
• so more photons will be trapped/light energy absrobed/more energy transferred to highe energy electrons
• more light dependent stage
• more photolysis of water
• more oxygen production

Question 32

An experiment was carried out to investigate the effect of leaf colour on the rate of photosynthesis laves placed in water naturally float but if small discs of leaes are punched out of leaves are in discs replaced by hydrogen carbon solution they will sink
the time for 15 light green leaf discs float to top of solution when illuminated from below can be determine and gives an estimate of rate of photsunthesis repeated for dark green leaf discs
Describe how would you use this technique to investigate the effect of wavelength on photosynthesis (4)

Answer 32

• change light wavelength
• record the time taken for discs to rise
• keep hydrogen carbon concentration constant/teperature constant/light intensity/heigh of solution
• same colour lead/area/diameter/size of discs/ species of plant

Question 33

An experiment was carried out to investigate the effect of leaf colour on the rate of photosynthesis laves placed in water naturally float but if small discs of leaes are punched out of leaves are in discs replaced by hydrogen carbon solution they will sink
the time for 15 light green leaf discs float to top of solution when illuminated from below can be determine and gives an estimate of rate of photsunthesis repeated for dark green leaf discs predict the result ou would expect when investigated effect of light of wavelength on photosythesis (2)

Answer 33

• less time/faster to rise at the blue/violet/shot and red/longer wavelengths
• skower to/more time to/does not rise in yellow/green wavelengths

Question 34

GP rises when plant is dark Tp decreases where plant is dark explain whyy (5)

Answer 34

• intially CO2 and RuBP reaction continues/Gp continues to be produced
• GP cannot be converted/reduced to TP
• because ATP and reduced NADP are needed
• ATP and reduced NADP only produced in light/not produced in dark
• therfore less TP available to regernate RuBP/ as it used to produce glucose
• therefore rate of reaction of carbon dioxide and RuBP decreases