Photosynthesis

Question 1

Which part of the chloroplast is the metabolic pathway involving CO2 located in (1)

Answer 1

STROMA

Question 2

Explain why the theoretical rate of photosynthesis is not achieved at higher light intensities (2)

Answer 2

Light intensity is no longer a limiting factor and so temperature becomes the limiting factor because it is a light independent reaction/involves enzymes

Question 3

Name 3 adaptation of a plant that lives in the shade/low light intensity (3)

Answer 3

1) More chloroplasts
2) More thylakoids in chloroplasts
3) Larger surface area of leaves

Question 4

Outline the ways in which heterotrophic organisms are dependent on plants (3)

Answer 4

Plants are the start of the food chain and Heterotrophs (animals) need to obtain organic material from plants

Plants produce glucose during photosynthesis and this glucose is used in respiration by heterotrophs (animals)

Question 5

Name the primary photosynthetic pigment in the photosytems (1)

Answer 5

Chlorophyll A

Question 6

Name the accessory pigment in photosytems (1)

Answer 6

Chlorophyll B

Question 7

State the advantage to the plant of having a range of accessory pigments in photosytems (1)

Answer 7

They’re 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 (1)

Answer 8

ATP

Question 9

The Calvin cycle occurs in the STROMA of the chloroplast.

Identify the enzyme that catalyses the fixation of carbon dioxide (1)

Answer 9

Rubisco

Question 10

The Calvin cycle occurs in the STROMA of the chloroplast.

Identify the first stable product of CO2 fixation (1)

Answer 10

GP or phosphoglycerate

Question 11

The Calvin cycle occurs in the STROMA of the chloroplast.

Identify the compound that is regenerated in the Calvin cycle so that more CO2 can be fixed (1)

Answer 11

RuBP or ribulose biphosphate

Question 12

The Calvin cycle occurs in the STROMA of the chloroplast.

Name the 2 different polysaccharides that can be synthesised from the end products of the light-independent stage of photosynthesis.

Answer 12

Starch and cellulose

Question 13

Name an enzyme associated with photosynthesis (1)

Answer 13

Rubisco

Question 14

Name a product of the light-dependent reaction that is used in the light-independent reaction (1)

Answer 14

ATP or reduced NADP

Question 15

Name a 3 carbon compound associated with photosynthesis (1)

Answer 15

Triose Phosphate (TP) or Glycerate-3-phosphate (GP)

Question 16

Name a compound that can be made from TP but is not part of the Calvin cycle (1)

Answer 16

Amino acid

Question 17

Name a 5 carbon compound associated with photosynthesis (1)

Answer 17

Ribulose Biphosphate (RuBP)

Question 18

Name a product of the light-dependent reaction that is not used in the light-independent reaction (1)

Answer 18

Oxygen

Question 19

Explain what is meant by an autotroph and heterotroph (2)

Answer 19

An autotroph can make organic molecules from inorganic molecules e.g. CO2

A heterotroph has to obtain its organic molecules that have been made by another organism by eating that organism

Question 20

The chloroplast contains fat droplets and act as a reserve of raw material for the chloroplast.

Suggest what this raw material might be used for in the chloroplast (1)

Answer 20

For membrane formation / for phospholipid for the membrane

Question 21

Describe how light is harvested in the chloroplast membranes (6)

Answer 21

1) Primary and accessory pigments are in a photosystem and the light energy (PHOTONS) are absorbed by pigment molecules
2) Electrons experience excitation and return to the pigment which facilitates the passing of energy/photons from 1 pigment to another
3) Energy/photons then pass to the reaction centre/chlorophyll A/ primary pigment
4) Here, accessory pigments allow a range of wavelengths to be absorbed

Question 22

One way to determine the rate of photosynthesis is to measure the uptake of carbon
dioxide.

Discuss why measuring carbon dioxide uptake may or may not give a better indication of
photosynthetic activity than measuring oxygen production. (2)

Answer 22

CO2 only measures the rate of the Calvin cycle whereas O2 measures the rate of the light dependent stage

Question 23

Carbon dioxide is given off by the plant when the light intensity is lower than 0.5 (random figure that is low).
Name the process that produces carbon dioxide in the plant (1)

Answer 23

(aerobic / anaerobic) respiration

Question 24

Explain the biochemical processes that are occurring in the
plant:
• as light intensity increases from 0 to 0.5.
• at light intensity 0.5.
• at light intensities greater than 0.5.

Answer 24

1) At 0, only respiration takes place
2) Between 0 and 0.5 the rate of respiration is greater than the rate of photosynthesis

3) At 0.5, 3 the rate of respiration equals rate of photosynthesis /
at compensation point

4) After 0.5, rate of photosynthesis is greater than rate of
respiration

Question 25

Name the products of the light-dependent stage of photosynthesis (3)

Answer 25

1) Reduced NADP
2) ATP
3) oxygen