Biology Unit 1 Booklet 4

Question 0

Describe the pathway of oxygen from an alveolus to the blood (3)

Answer 0

Diffuses (1)
Through the alveolar epithelium (1)
Into blood via the capillary endothelium (1)

Question 1

Adaptations of human lungs in relation to Fick’s law (6)

Answer 1

Small diffusion pathway (1)
Caused by thin squamous epithelial cells (1)
Large concentration gradient (1)
Caused by constant removal of oxygen by the blood and constant renewal of oxygen in the alveoli (1)
Large surface area (1)
Caused by numerous, small alveoli (1)

Question 2

Explain how ventilation maintains a concentration gradient (3)

Answer 2

Air high in oxygen is continuously entering the alveoli (1)
Air low in oxygen is continuously being removed from the alveoli (1)
Blood high in oxygen is removed (1)

Question 3

Inspiration (5)

Answer 3

Intercostal muscles contract (1)
Ribs move up and out (1)
Diaphragm muscles contract and the diaphragm flattens (1)
Volume increase (1)
Pressure decreases relative to atmospheric pressure so air moves in (1)

Question 4

Expiration (5)

Answer 4

Intercostal muscles relax (1)
Ribs move down and in (1)
Diaphragm returns to dome shape (1)
Volume decreases (1)
Pressure increases relative to atmospheric pressure so air moves out (1)

Question 5

Explain how paralysis of diaphragm leads to breathing difficulties (2)

Answer 5

Diaphragm will not flatten (1)

So lung volume will not increase (1)

Question 6

Course of TB (6)

Answer 6

Bacteria grow in upper regions of lungs where there is a plentiful supply of oxygen (1)
White blood cells accumulate at site of infection (1)
Leads to inflammation and enlargement of lymph nodes (1)
Years later bacteria may reemerge to cause a second infection (1)
Bacteria can destroy lung tissue which can result it cavities and scar tissue (1)
Sufferers can cough up damaged tissue with blood (1)

Question 7

Effects of allergies in asthma (6)

Answer 7

Allergens cause white blood cells lining the bronchioles to release histamines (1)
Lining of airways become inflamed (1)
Cells of epithelial lining secretes large quantities of mucus (1)
Fluid leaves capillaries and enters airways (1)
Muscles surrounding bronchioles contract and constrict airways (1)
Therefore lack of ventilation means concentration gradient for the diffusion of oxygen is not removed (1)

Question 8

Explain why during and asthma attack less oxygen diffuses into the blood (4)

Answer 8

Bronchioles restricted (1)
Air in alveoli is not replaced so less oxygen (1)
Concentration gradient is not maintained (1)
Rate of oxygen diffusion is lower (1)

Question 9

Explanation if symptoms of asthma (4)

Answer 9

Difficulty in breathing due to constriction of bronchioles (1)
Wheezing sound caused by air passing through restricted bronchioles (1)
Tight feeling in the chest is a consequence of not being able to ventilate the lungs adequately (1)
Coughing is a reflex response to obstructed bronchioles (1)

Question 10

Effects of emphysema (6)

Answer 10

Elastin in lung tissue has been permanently stretched (1)
Lungs no longer able to force air out of alveoli (1)
Therefore lack of ventilation means concentration gradient cannot be maintained (1)
Surface area of alveoli is reduced and they sometimes burst (1)
Diffusion of gases is less efficient (1)
I.e. rate of diffusion is lower (1)

Question 11

Explanation of symptoms of emphysema (3)

Answer 11

Shortness of breath resulting from difficulty in inhaling due to loss of elasticity in the lungs (1)
Chronic cough due to body’s effort to remove damaged tissue (1)
Bluish skin coloration is due to low levels of oxygen in blood as a result of poor gas exchange (1)

Question 12

Effects of pulmonary fibrosis (4)

Answer 12

Elastin may be destroyed so lungs no longer able to force air out of alveoli (1)
Therefore lack of ventilation mans the concentration gradient cannot be maintained (1)
Scar tissue (1)
Increases length of diffusion pathway (1)

Question 13

Explanation of the symptoms of pulmonary fibrosis (4)

Answer 13

Shortness of breath due to a considerable volume of lungs being occupied by fibrous tissues (thickened epithelium means diffusion pathway is increased) (1)
Chronic dry cough because fibrous tissue creates an obstruction in the airways (1)
Pain and discomfort in chest are the consequence of pressure and scarring due to coughing (1)
Weakness and fatigue result from reduced intake of oxygen in the blood (1)

Question 14

Explain why people with lung disease may get easily tired (5)

Answer 14

Slow rate of oxygen diffusion (1)
Less oxygen in blood (1)
Less delivered to cells for respiration (1)
Less ATP is produced (1)
Less muscles contractions (1)