OESWTE: Gas exchange in humans and plants

Question 1

What three features of the human lungs maximise the rate of diffusion:

Answer 1

• Short diffusion pathway
• Large surface area
• Steep concentration gradient of oxygen and carbon dioxide

Question 2

Explain the factor of short diffusion pathway:

Answer 2

• The alveolar epithelium is one cell thick
• Gases have a short diffusion distance so gas exchange is quick and efficient.

Question 3

Explain the factor of large surface area:

Answer 3

• The large number of alveoli increases the surface area available for oxygen and carbon dioxide to diffuse across.

Question 4

Explain the factor of steep concentration gradient of oxygen and carbon dioxide:

Answer 4

• The constant ventilation and flow of blood
• Oxygenated blood is brought away from the alveoli and deoxygenated blood is brought to them.
• Maintains concentration gradient needed for gas exchange

Question 5

Explain inhalation in the human lungs:

Answer 5

• Diaphragm contracts
• External intercostal muscles contract
• Thorax volume increases, pressure decreases
• Air is forced into the lungs

Question 6

Explain exhalation during exercise in the human lungs:

Answer 6

• Diaphragm relaxes
• Internal intercostal muscles contract
• Thorax volume decreases, pressure increases
• Air is forced out of the lungs

Question 7

Single celled organisms absorb and release gases by diffusion through their ___________.

Answer 7

Cell-surface membranes

Question 8

What is the main gas exchange surface in plants?

Answer 8

Mesophyll cells

Question 9

In plants what are the pores called which gases move in and out of?

Answer 9

Stomata

Question 10

What cells control the opening and closing of the stomata?

Answer 10

Guard cells

Question 11

Why do insects have an exoskeleton?

Answer 11

• Protection
• Prevent water loss (with lipid layer)

Question 12

What do insects have instead of lungs?

Answer 12

Tracheal system

Question 13

What are spiracles?

Answer 13

• Round, valve-like openings along the abdomen of an insect

Question 14

What substances enter and leave via spiracles?

Answer 14

• Oxygen
• Carbon Dioxide

Question 15

What is the trachea?

Answer 15

A network of internal tubes

Question 16

In an insects tracheal system, what is the purpose of trachea tubes having rings?

Answer 16

• Strength the tubes
• Keep the tubes open

Question 17

Explain the anatomy of an insects tracheal system:

Answer 17

Spiracles (holes) along the insects abdomen.
Trachea attach to spiracles.
Trachea branches into tracheoles.

Question 18

What is the role of the tracheoles in an insects tracheal system?

Answer 18

Deliver oxygen to respiring cells.

Question 19

What are the three methods of moving gases into the tracheal system in insects?

Answer 19

1) Diffusion
2) Mass transport
3) Anaerobic respiration

Question 20

Explain diffusion as a method of moving gases into the tracheal system in insects:

Answer 20

• Respiring cells use up oxygen and produce carbon dioxide
• Concentration gradient from the tracheoles to the atmosphere

Question 21

Explain mass transport as a method of moving gases into the tracheal system in insects:

Answer 21

• Insects abdominal muscles contract and relax

Question 22

Explain anaerobic respiration as a method of moving gases into the tracheal system in insects:

Answer 22

• When insects are in flight their cells respire anaerobically to produce lactate.
• Lactate lowers water potential of the cells, so water moves from the tracheoles into the cells (osmosis)
• Decreases volume of the tracheoles so more air is drawn in.

Question 23

Give the three insect adaptations to prevent water loss:

Answer 23

• Small surface area:volume ratio for water to evaporate from
• Waterproof exoskeleton
• Spiracles can open and close

Question 24

When a plant has sufficient water it enters the guard cell making them turgid. This _____ the stomatal pore.

Answer 24

Opens

Question 25

If a plant is dehydrated the guard cells become flaccid. This _____ the stomatal pore.

Answer 25

Closes

Question 26

Give the 5 adaptations of xerophytes:

Answer 26

1) Stomata are sunk in pits to trap water vapour (reduces evaporation) 2) Layer of hairs on the epidermis to trap water around the stomata 3) Stomata is inside curled leaves (protects them from wind) 4) Reduced number of stomata 5) Thick, waxy, waterproof cuticle

Question 27

Give an example of an area with a low partial pressure:

Answer 27

Respiring tissues

Question 28

Give an example of an area with a high partial pressure:

Answer 28

Alveoli

Question 29

What happens to oxygens in areas of low partial pressure?

Answer 29

Oxygen is offloaded

Question 30

What happens to oxygen in areas with a high partial pressure?

Answer 30

Oxygen is loaded

Question 31

What is the advantage of the alveolus' walls containing the protein elastin?

Answer 31

Helps the alveoli return to their normal shape after inhaling and exhaling air.

Question 32

What are the three adaptations of the alveoli that increase the rate of diffusion?

Answer 32

- Alveolar epithelium is only one cell thick (short diffusion pathway) - Large surface area for gas exchange - Good blood supply (allows steep concentration of oxygen and carbon dioxide)

Question 33

Define tidal volume:

Answer 33

The volume of air in each breath.

Question 34

Define ventilation rate:

Answer 34

The number of breaths per minute.

Question 35

What is tuberculosis caused by?

Answer 35

Bacteria

Question 36

What is the impact of a reduced tidal volume?

Answer 36

Less air can be inhaled with each breath

Question 37

Define FVC:

Answer 37

Forced vital capacity - The maximum volume of air it is possible to breathe out after a deep breath in.

Question 38

Define FEV:

Answer 38

Forced expiratory volume - The maximum volume of air that can be breathed out in 1 second.

Question 39

Insect trachae provide tubes of air. How does this increase the efficiency of gas exchange?

Answer 39

Means gases can diffuse quickly into tissues.