Paper 2 - Respiration and Gas Exchange

Question 1

What is the role of diffusion in gas exchange?

Answer 1

• To distribute O2 to cells for aerobic respiration and produce ATP energy and remove CO2 as a waste product
• For CO2 to be taken in for photosynthesis in plants and remove O2 as a waste product

Question 2

Explain gas exchange of carbon dioxide and oxygen in relation to
respiration

Answer 2

• O2 in taken in via stomata for aerobic respiration
• CO2 is excreted as a waste product of metabolism

Question 3

Explain gas exchange of carbon dioxide and oxygen in relation to photosynthesis

Answer 3

• CO2 in taken in via stomata for photosynthesis
• O2 is excreted via the stomata as a waste product of plant metabolism

Question 4

How is the structure of the leaf adapted for gas exchange?

Answer 4

• Thin for fast diffusion
• Air spaces in spongey mesophyll layer for fast diffusion
• Large surface area for diffusion
• Many stomata for gas exchange

Question 5

Describe the role of stomata in gas exchange

Answer 5

• Guard cells move to allow gases to pass in and out
• CO2 and O2 are examples of gases that are exchanged through the stomata

Question 6

How does respiration continue during the day and night

Answer 6

• Light is not required for aerobic respiration
• Breaks down starch molecules into glucose to be used to produce ATP energy is aerobic respiration

Question 7

How does the net exchange of carbon dioxide and oxygen depends on the intensity of light?

Answer 7

• If light intensity is high, CO2 intake is increased for photosynthesis
• If light intensity is high, more O2 is excreted to due more photosynthesis

Question 8

Describe an experiment to investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator

Answer 8

• Place plants in 3 test tubes of water and have 1 test tube with just water as control
• Wrap one is aluminium
• Wrap one in muslin
• Place lamp 10cm away from all of them
• Add 1 spatula of hydrogen-carbonate indicator to each
• The test tube wrapped in foil’s solution will turn yellow due to the presence of C02
• The test tube wrapped in muslin’s solution will turn purple due to the lack of CO2
• The test tube not wrapped in anything will ain orange
• Control will remain orange
• Repeat with the lamp at different distances from the plant