gas exchange 2

Question 1

Describe the process of inhalation in humans

Answer 1

1- Diaphragm contracts and flattens

2- External intercostal muscles contract, and internal intercostal muscles relax

3- Ribcage pulled up and out

4- So volume of thorax increases

5- So pressure in thorax decreases

6- Pressure in thorax lower than atmospheric, so air moves into lungs down the pressure gradient

Question 2

What are the three most key important features of an efficient gas exchange system

Answer 2

1- Large surface area

2- Short diffusion distance / pathway

3- Concentration gradient maintained

Question 3

Describe the process of exhalation in humans

Answer 3

1- Diaphragm relaxes and domes

2- External intercostal muscles relax, and internal intercostal muscles contract

3- Ribcage pulled in and down

4- So volume in thorax decreases

5- So pressure in thorax increases

6- As pressure in thorax is greater than in atmosphere, air moves down pressure gradient out of lungs

Question 4

Pulmonary ventialation rate equation

Answer 4

PVR = tidal volume x breathing rate

Question 5

Tidal volume equation

Answer 5

PVR / breathing rate

Question 6

Breating rate equation

Answer 6

PVR / tidal volume

Question 7

Explain how the human gas exhange system is specialised - for large surface area

Answer 7

Large number of alveoli

Question 8

Explain how the human gas exhange system is specialised - for short diffusion distance/pathway

Answer 8

1- Alveoli epithelium cell is one cell thick

2- Capillary walls are one flattened cell thick

Question 9

Q
Explain how the human gas exhange system is specialised - for maintaining high concentration gradient

Answer 9

Constant flow of blood through capillary network
Ventilation in lungs replenishes air

Question 10

How are single celled organisims speciallised for gas exchange

Answer 10

1- Cells are flattened and long, so large surface area and reduced diffusion distance/pathway

2- Oxygen quickly used in respiration so maintains a high concentration gradient

Question 11

Explain how the fish gas exhange system is specialised - for large surface area

Answer 11

Large number of gill fillaments and lamellae

Question 12

Q
Explain how the fish gas exhange system is specialised - for short diffusion distance/pathway

Answer 12

Lamellae are thin
Many capillaries in the lamellae

Question 13

Explain how the fish gas exhange system is specialised - for concentration gradient maintained

Answer 13

counter-current mechanism

Question 14

Explain the counter-current mechanism

Answer 14

1- Blood and water flow in opposite directions

2- Blood always passes water with higher oxygen concentration

3- Oxygen diffusion gradient maintained across entire length of gill

4- So diffusion occurs across entire length of gill

Question 15

Explain how the insect gas exhange system is specialised - for large surface area

Answer 15

Tracheoles are highly branched

Question 16

Explain how the insect gas exhange system is specialised - for short diffusion distance/pathway

Answer 16

Tracheoles are highly branched
Tracheole walls are thin and permeable to oxygen
Many spiracles

Question 17

Describe the movement of oxygen in insect gas exhange systems

Answer 17

A
Spiracles open to allow oxygen to move by diffusion down diffusion gradient which then lead to trachea to traceoles to cells

Question 18

Describe adaptations to insect gas exchange system when anaerobically respiring

Answer 18

Water moves out of tracheoles, reducing diffusion distance of oxygen in water

Question 19

Describe abdominal pumping

Answer 19

1- Only occurs when CO2 concentration very high

2- Pumping raises pressure in body

3-So carbon dioxide moves out down pressure gradient into atmosphere

Question 20

How is the insect gas exhange system adapted to prevent water loss

Answer 20

1- Chitin exoskeleton is impermeable

2- Spiracles close during inactivity

3- Spiracle surrounded by hairs which traps a layer of air saturated with water, decreasing concentation gradient

Question 21

How are plants specialised to maximise gas exchange

Answer 21

1- Large surface area of leaves, so greater number of stomata

2- Many stomata, so short diffusion distance to/from spongy mesophyll cells

3- Thin leaves, so short diffusion distance to/from spongy mesophyll cells

4- Carbon dioxide quickly used in photosythesis to maintain high concentration gradient

Question 22

How are plants specialised to reduce water loss

Answer 22

1- Thicker waxy cuticle to increase diffusion distance of water, and so reduce evaportation of water

2- Stomata sunken in pits

3- Stomata surrounded by hairs
4- Leaves are rolled

–> All trap water and decrease the water potential gradient

5- Leaves are spines so reduces the SA:V ratio

Question 23

How is lung capacity measured?

Answer 23

By a spirometer.

Question 24

What is normally the tidal volume?

Answer 24

0.5 dm^3.

Question 25

What is the total lung capacity?

Answer 25

Vital capacity + residual volume.

Question 26

What is normally the total lung capacity?

Answer 26

5-6 dm^3.

Question 27

What are the units for pulmonary ventilation?

Answer 27

dm^3 min^-1

Question 28

How do bronchitis and asthma affect gas exchange?

Answer 28

1- Reduce the lumen size of the bronchioles. 2- Meaning less air can travel to the alveoli. 3- Means there is a smaller concentration gradient. 4- And less oxygen for gas exchange.

Question 29

What are xerophytic plants adapted to do?

Answer 29

Survive in environments with limited water.

Question 30

Answer 30

EITHER 1. Low/slow growth; 2. Due to smaller number/area of stomata (for gas exchange); OR 3. Growth may continue at lower water potentials; 4. (Due to) adaptations in enzymes involved in photosynthesis/metabolic reactions;

Question 31

Answer 31

Stomata close; Less carbon dioxide (uptake) for less photosynthesis/glucose production;

Question 32

Describe the gross structure of the human gas exchange system and how we breathe in and out.

Answer 32

Named structures – trachea, bronchi, bronchioles, alveoli; Above structures named in correct order OR Above structures labelled in correct positions on a diagram; Breathing in – diaphragm contracts and external intercostal muscles contract; (Causes) volume increase and pressure decrease in thoracic cavity (to below atmospheric, resulting in air moving in); Breathing out - Diaphragm relaxes and internal intercostal muscles contract; (Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric, resulting in air moving out);

Question 33

Curve A could be used to find the total volume of air that this person could breathe out in one complete breath. Describe how. (2)

Answer 33

- Extrapolate/ extend the curve - Read off where curve flattens

Question 34

adaptations of xerophytes

Answer 34

1- Curled leaves to trap moisture to increase local humidity (pointing to the overall curled structure of the leaf). 2- Hairs to trap moisture to increase local humidity (pointing to the numerous small projections on the inner surface of the curled leaf). 3- Sunken stomata to trap moisture to increase local humidity (pointing to depressions on the inner surface where the stomata would be located). 4- Thicker cuticle to reduce evaporation (text box, no specific pointer within the image, but refers to a general adaptation) 5- Longer root network to reach more water (text box, no pointer, as it describes a root adaptation not visible in a leaf cross-section).

Question 35

where does most photosynthesis occur in a leaf?

Answer 35

palisade mesophyll

Question 36

why do the stomata close at night?

Answer 36

to reduce water loss via evaporation -> as photosynthesis doesn't happen at night