Biology Chap 7 Worksheet Ans

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Worksheet 31 answers:
1. a) Nostril _ nasal cavity _ pharynx _ larynx _ trachea _ bronchi _ bronchioles

b) The lungs are efficient for gaseous exchange because:
• The lungs are made of numerous alveoli which provide a large surface area for gaseous exchange
• The surfaces of the alveoli are moist for gases to dissolve • The alveolar wall is thin consisting of one layer of epithelial cells • Each alveolus is surrounded by numerous capillary network

c) i) Because they have an anti-sticking chemical called a surfactant covering their surfaces. ii) This chemical acts by reducing the surface tension, hence keeps the alveoli open

2. a) A. Epithelial cell of alveolus B. Thin film of moisture / Alveolar fluid C. Red blood cell D. Endothelial capillary

b) Diffusion

c) R – Deoxygenate blood S – Oxygenated blood.

d) In the lungs and tissue

e) i) Deoxygenated blood has less oxygen than the alveolar air.

ii) This causes oxygen to diffuse out of the alveolus into the blood capillaries.

f) Oxygen molecules pass through and dissolve in the thin film of moisture in the alveolar wall. The oxygen then pass through the thin layer of alveolar epithelial cells and the endothelial cells of capillary wall.

g) Oxygenated blood has more oxygen and less carbon dioxide than the tissue.

3. a) A – Water B – Carbonic acid C – Carbonic anhydrase D – Haemoglobinic acid

b) i) Method I: CO2 in the tissue diffuses into the red blood cell. Method II: CO2 reacts with water to form carbonic acid.

ii) - Catalyses a reaction between carbon dioxide and water to form carbonic acid - Catalyses the dissociation of carbonic acid into hydrogen carbonate ions and hydrogen ions.

iii) To balance the electrical charge. This is known as the chloride shift.

c) It helps to maintain the blood pH by removing hydrogen ions from solution.

d) - As dissolved carbon dioxide in the blood plasma
- Carbon dioxide combine with haemoglobin to formed carbamino-haemoglobin

Worksheet 32 answers:
1.a) (i) Llama is an animal living at high altitude where there is a reduced air pressure. At this altitude the Po2 is lower compared to the sea level. The difference of Po2 in the air and the llama’s lungs is lowered thus less oxygen can diffuse across the alveoli. Thus this makes it difficult to load haemoglobin. The llama’s haemoglobin therefore has a high affinity of oxygen to compensate for this. Therefore the dissociation curve for llama is to the left of the human haemoglobin.

(ii) Mouse is a small animal. It has a larger surface area to volume ratio than human. The mouse loses heat rapidly. To compensate for this it has a higher metabolic rate than human to help generate heat. To keep tissues supplied with oxygen the haemoglobin of the mouse has a lower affinity for oxygen and therefore unloads the gas quickly to the tissues. The reduced affinity does not adversely affect the loading of haemoglobin as the partial pressure of oxygen (Po2) of air is - more than enough to fully saturate the haemoglobin.

2. a) Discuss the difference in site, structures and the functions of haemoglobin and myoglobin. Haemoglobin is found in red blood cells but myoglobin is found in muscles. Haemoglobin consists of four subunits of polypeptide, 2-αand 2-ß polypeptide however myoglobin is made up of only one polypeptide chain. In each subunits of haemoglobin there is a haem group that can binds with one-oxygen molecules. Thus one haemoglobin can carry a maximum of 4 oxygen molecules. Since myoglobin contains only one haem group thus it can binds only with one molecule of oxygen. Haemoglobin carry oxygen in the bloodstream but myoglobin keeps oxygen in muscles.

b) The myoglobin’s oxygen dissociation curve is hyperbolic in shape but the haemoglobin curve is sigmoid. At low Po2 that is below 20 mm Hg, the percentage saturation of myoglobin with oxygen decreases...
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