Gas Exchange

Question 1

Define diffusion

Answer 1

The net movement of molecules from an area of high concentration to an area of low concentration down their concentration gradient

Question 2

What gas do plants need to take in for aerobic respiration?

Answer 2

Oxygen (O2)

Question 3

What gas to plants need to remove from respiration?

Answer 3

Carbon dioxide (CO2)

Question 4

What gas do plants need to take in for photosynthesis?

Answer 4

Carbon dioxide (CO2)

Question 5

What gas do plants need to remove from photosynthesis?

Answer 5

Oxygen (O2)

Question 6

Give 3 adaptations of leaf tissue for gas exchange

Answer 6

• Stomata (pores) allow diffusion of gases in and out of the plant
• Thin to shorten the diffusion distance
• Air spaces in the spongy mesophyll layer allow gases to diffuse

Question 7

Why don’t plants keep the stomata open permanently?

Answer 7

Plants need to close the stomata to reduce water loss

Question 8

Draw a graph to show how photosynthesis and respiration are affected by light intensity

Answer 8

Question 9

Why do plants release more CO2 compared to O2 at night?

Answer 9

• Respiration continues during the night whereas photosynthesis does not
• Respiration releases CO2 and photosynthesis releases O2

Question 10

Describe the general structure of the lungs

Answer 10

• Trachea branches into two bronchi
• Bronchi branch into bronchioles
• Bronchioles terminate in alveoli

Question 11

Describe the structure of an alveolus

Answer 11

• Small sacs with capillaries around them
• Contain a surfactant so walls don’t stick together and so gases can dissolve to help diffusion

Question 12

What is the purpose of the pleural membrane?

Answer 12

The pleural membrane covers the lungs, reduces friction and keeps the lungs moist

Question 13

What are the intercostal muscles?

Answer 13

They are a group of muscles found between the ribs that are involved in breathing by changing the size of the thorax

Question 14

How do the diaphragm and intercostal muscles work together during expiration (breathing out)?

Answer 14

Expiration:
- Diaphragm relaxes and moves up
- External intercostal muscles relax
- Volume in the thorax decreases and air moves out

Question 15

How do the diaphragm and intercostal muscles work together during inspiration (breathing in)?

Answer 15

Inspiration:
- Diaphragm contracts and moves down
- External intercostal muscles contract
- Volume in the thorax increases and air moves in

Question 16

Give 3 health issues caused by smoking

Answer 16

• Cancer
• Bronchitis
• Coronary heart disease

Question 17

How does smoker’s cough arise?

Answer 17

• Cilia on cells lining the trachea waft mucus containing dirt out of the lungs
• Smoking can kill cells lining the trachea
• A build-up of mucus in the lungs can cause people to develop smoker’s cough