F4 Biology 2nd Term WS 04 ans: 7 Gas Exchange in Human III

7 Gas Exchange in Human III

2^nd WS 04

Textbook exercise (P. 28 - 32)

M.C.

1	2	3	4	5	6	7	8	9	10	11
B	B	B	A	D	A	B	C	C	C	B

Q. 17      

(a)    Y: Pleural membrane (1)

        It secretes pleural fluid   (1)

        which reduces the friction during breathing action (1)

(b)    (atmosphere) à nasal cavity à pharynx à larynx à trachea

à bronchi à bronchioles à (air sacs)   (2)                                           

(c)   The volume of air being inhaled decreases (1).

        Less fresh air combines with the remaining gas,

maintaining a high concentration of carbon dioxide in air sacs (1)

        As a result, the concentration gradient of carbon dioxide between

        the air in the air sacs and the blood become less steep (1),

        slowing down the removal of carbon dioxide from the blood. (1)

        OR

        The volume of air being exhaled decreases,

which reduces the removal of carbon dioxide from the lung (1).

Concentration of carbon dioxide in air sacs is maintained to be higher (1).

As a result, the concentration gradient of carbon dioxide between

        the air in the air sacs and the blood become less steep (1),

        slowing down the removal of carbon dioxide from the blood. (1)

        Communication (C) (1)

Q.18

(a)    Any TWO sets of the followings:

The wall of A is very thin (1)

for reducing the diffusion distance (1)

A has a rich supply of blood capillaries (1).

This can transport gases to or from the air sacs rapidly

/ maintain a high concentration gradient of gases between A and the blood (1).

Lung tissues are composed of numerous air sacs (1),

                so there is a large surface area for gaseous exchange / diffusion of gases (1)

(b)    During ventilation / breathing, parts of the gases in the lung are replaced by fresh air (1).

        And fresh air contains high level of oxygen (1)

(c)    (i)     

Title (0.5)

Reasonable setup: inverted gas jar, collecting gas under water, rubber tubing (1)

Labels: water / water trough, breathing out, rubber tubing,

collected exhaled air (Any 3) (1.5)

                Quality of drawing (1)

        (ii)    Place a burning candle into the air sample (1).

                Compare the burning time of the two samples (1).

Q. 16

(a)    (i)     The diaphragm lowers / flattens,                                                                                         1

                 so the volume of the lungs increases.                                                                                  1

         (ii)    Air is entering the lungs.                                                                                                     1

(b)    60/ 3.3                                                                                                                                         1

         = 18.2 breath/min                                                                                                                        1