photosynthesis and respiration

Question 1

scientists studied the rate of carbon dioxide uptake by grape leaves.
Grape leaves have stomata on the lower surface but no stomata on the upper surface

the scientist recorded the carbon dioxide uptake by the leaves with three different treatments

suggest the purpose of each of three-leaf treatments

Answer 1

treatment 1: to allow CO2 uptake as normal/ it means that the stomata are open

treatment 2: to stop CO2 uptake through the stomata

treatment 3: to make sure the sealing grease is effective/ to stop all CO2 uptake

Question 2

the stomata close when the light is turned off

Explain the advantage of this to the plant

Answer 2

when the stomata are open, water is lossed when it closes water loss via the stomata stops

Question 3

treatment 2 shows that even when the lower surface of the leaf is sealed there is still some uptake of carbon dioxide

suggest how this uptake of CO2continues

Answer 3

CO2 diffuses into the plant via the upper surface through the CUTICLES

Question 4

in both treatment 1 and treatment 2, the uptake of CO2 falls to zero when the light is turned off

EXPLAIN WHY

Answer 4

when the lights are turned off there is no longer a need for CO2 as photosynthesis can not occur so the stomata closes

This means a diffusion gradient into the leaf is no longer maintained for CO2

Question 5

what measurements should the student have taken to determine the rate of photosynthesis

Answer 5

the concentration of O2 AND time

Question 6

suggests and explain why the rate of photosynthesis was low between 525 and 575nm wavelengths of light

Answer 6

light in this wavelength is green light and green light is reflected not absorbed

Question 7

explain why the scientists measured the rate of production of oxygen in this investigation

Answer 7

O2 is produced in the light-dependent reaction via photolysis

it follows that the faster o2 is produced the faster the light dependant reaction is

Question 8

the scientists suggested that mutant plants producing more chlorophyll b would grow faster than normal plants in all light intensities

Explain how these data support this suggestion

Answer 8

1. have a faster production of ATP and NADP from the light dependant stage
2. so they have a faster light-independent reaction
3. so more sugars e.g. glucose is produced that can be used in respiration
4. so more energy is available for growth

Question 9

give two factors that could be limiting the rate of photosynthesis in the sun plant between points A and B on the figure

Answer 9

temperature and CO2

Question 10

use the information in the figure to explain how the shade plant is better adapted to growing at low light intensities

Answer 10

the lower rate of respiration

and so more glucose is available for growth

Question 11

describe how acetyl-coenzyme A is formed from pyruvate

Answer 11

pyruvate is oxidised to form acetate to form hydrogen and carbon dioxide

acetate then binds with coenzyme A to form acetyl coenzyme A

Question 12

explain why converting pyruvate to lactate allows the continual production of ATP during anaerobic repsiration

Answer 12

pyruvate to lactate accepts the hydrogen from reduced NAD and is reduced itselt

This allows NAD to be reformed and so glycolysis can continue

Question 13

for the first 10 minutes, the tap attached to tube A was left open and the syringe form tube B was removed

suggest three reasons why the apparatus was left for 10 minutes

Answer 13

1. to allow the seeds to equilibrate to the new environment
2. to allow the apparatus to stabilise to the change in pressure/ pressure changes
3. to allow the respiration rate of seed to stabilise

Question 14

during the experiment, the coloured liquid in the tubing moved towards tube B

Explain why

Answer 14

o2 is taken up

CO2 given out is absorbed by the KIG

so pressure falls in B

Question 15

what do you do when the question metions O2

Answer 15

O2 acts as the terminal electron acceptor and bind with electrons and protons to form water

Question 16

use your knowledge of photosynthesis and respiration to describe and explain how the concentration of carbon dioxide in the air changes

• over a period of 24 hours
• at different heights above ground

Answer 16

1. high concentration of CO2 at night time is linked to the plants respiring in darkness
2. no photosynthesis in the dark only in the light
3. light, the rate of photosynthesis is greater than the rate of respiration so CO2 concentrations decrease
4. CO2 decreases with hight (due to plants at ground level having less photosynthetic tissue)

Question 17

iron deficiency results in a decrease in the uptake of carbon dioxide

Explain why

Answer 17

1. less triose phosphate converted to RUBP
2. so CO2 is not needed to combine with RUBP/less triose phosphate so less RUBP

Question 18

explain why it is important to keep conditions the same

Answer 18

so any differences are due to (insert independent variable)

Question 19

what is important to remember when answering a question that asks why the rate of CO2 uptake decreases

Answer 19

less Gp is converted to triose phosphate

so less triose phosphate is converted to ribulose biphosphate therefore CO2 is needed to combine with RUBP

Question 20

Plants produce ATP in their chloroplasts during photosynthesis

They also produce ATP during respiration
Explain why it is important for plants to produce ATP during respiration in addition to during photosynthesis

Answer 20

1. When it is dark e.g. nighttime, no ATP is being produced as photosynthesis does not occur
2. some plant tissue is unable to photosynthesis and produce ATRP
3. plants use more ATP than produced in photosynthesis
4. for active transport
5. and for synthesis of organic substances such as glucose

Question 21

describe the light dependent reaction

Answer 21

Question 22

Answer 22

Ampk inhibits the production of acetyl coenzyme A to Malonyl-CoA

therefore more fatty acid is moved to the mitochondira

so fatty acids can be used in oxidation to produce ATP

Question 23

the scientists then compared the length of time that the control mice and the trained mice could carry out prolonged exercise

The trained mice were able to exercise for a longer time period than the control mice

Answer 23

1. (More aerobic respiration) produces more ATP;
2. Anaerobic respiration delayed;
3. Less or no lactate;