Gas Exchange (humans)

Question 1

how is a leaf adapted for gas exchange?

Answer 1

• thin, shorter diffusion distance for oxygen and carbon
• large SA to increase rate of absorption of sunlight and gases
• internal air spaces in spongy mesophyll for larger internal SA:vol ratio
• stomata

Question 2

give the colours of hydrogen carbonate indicator.

Answer 2

high CO2 conc = yellow
medium CO2 conc = red
low CO2 conc = purple

Question 3

describe the function of the pleural membrane

Answer 3

a thin, moist membrane lining the outside of lungs for:

• lubrication to reduce friction
• to stick outside of lungs to chest cavity for lung to follow chest movement

Question 4

describe the function of the intercostal muscles, as well as their movement during inhalation and exhalation.

Answer 4

muscles between the ribs which control their movement during inhalation and exhalation.

• inhalation: contract and make the ribcage lift upwards
• exhalation: relax

Question 5

describe the function of the diaphragm, as well as its movements during inhalation and exhalation.

Answer 5

a sheet of connective and muscle tissue at the bottom of the thorax that helps change the volume of the thorax to allow inhalation and exhalation

• inhale: contracts (moves downwards)
• exhale relaxes (moves upwards)

Question 6

give 3 adaptations of alveoli

Answer 6

• large SA
• good blood supply
• single cell walls

Question 7

name 3 harmful substances in cigarettes.

Answer 7

nicotine, tar, carbon monoxide

Question 8

describe how nicotine may lead to strokes or heart attacks.

Answer 8

• narrows blood vessels
• increasing blood pressure
• damages lining of arteries
• increases heart rate
• this can cause blood clots to form in the arteries

Question 9

describe how tar may cause chronic bronchitis

Answer 9

• stimulates goblet cells + mucus glands to enlarge
• producing more mucus
• destroys cilia
• mucus builds up, blocking smaller bronchioles and causing infection

Question 10

describe how carcinogens in tar can be harmful

Answer 10

they can change the sequence of the bases DNA and cause mutations, leading to uncontrolled cell division (cancer)

Question 11

describe how carbon monoxide in cigarettes may be damaging

Answer 11

carbon monoxide binds to haemoglobin more readily than oxygen, forming carboxyhemoglobin, so less oxygen will be carried around the body

Question 12

describe emphysema and its effect on alveoli.

Answer 12

if the lungs are infected with a harmful substance, phagocytes that enter the lung release elastase, an enzyme that breaks down elastic fibres in the alveoli.

• become less elastic
• cannot stretch and so burst
• decreased surface area.