1. Objective:
1. Diagram 1 shows diffusion of gas Y from an alveolus to a blood capillary.
Diagram 1
Which of the following is true about the difference in the concentration of gas Y
of a healthy person and a cigarette smoker?
Healthy individual Cigarette smoker
A Higher Higher
B Lower Higher
C Lower Lower
D Higher Lower
2. Which artery carries blood with the lowest oxygen concentration?
A. The pulmonary artery
B. The mesenteric artery
C. The hepatic artery
D. The renal artery
3. Diagram 2 shows part of the systemic circulatory system.
Diagram 2
Which of the following is the type of blood and correct blood vessel for blood
that flows from organ X to the heart?
Type of blood Blood vessel
A Deoxygenated Pulmonary artery
B Deoxygenated Vena cava
C Oxygenated Pulmonary vein
D Oxygenated Aorta

2. 4. The following statements are the characteristics of blood transported by a blood
vessel in the human body.
 High concentration of oxygen
 Low concentration of carbon dioxide
 High blood pressure
What is the blood vessel?
A. Aorta
B. Vena cava
C. Pulmonary artery
D. Pulmonary vein
5. Which of the following processes occurs during gaseous exchange between the
alveolus and the blood capillary?
A. Active transport
B. Simple diffusion
C. Osmosis
D. Facilitated diffusion

3. Structure:
1. Diagram 1 shows the structure of respiratory system in human.
Diagram 1
(a) On Diagram 1, draw labeled arrow ( ) to show the direction of
 Blood flow
 Oxygen diffusion
 Carbon dioxide diffusion [ 3 marks ]
(b) Explain why the diffusion of oxygen occur at the alveolus.
______________________________________________________________
______________________________________________________________
______________________________________________________________
[ 2 marks ]

4. 2. Diagram 2 shows the exchange of respiratory gases X and Y between the alveolus,
blood capillary and the body cells and the transport of the gaseous.
Diagram 2
(a) (i) Name the gas X and Y.
Gas X: ___________________________________________________
Gas Y: ___________________________________________________
[ 2 marks ]
(ii) Explain how the alveolus is structured to increase the efficiency of
gaseous exchange.
________________________________________________________
________________________________________________________
________________________________________________________
[ 2 marks ]
(b) Explain the difference between the concentration of gas X and Y in blood
vessel Q.
____________________________________________________________
____________________________________________________________
____________________________________________________________
[ 2 marks ]

5. (c) The concentration of gas X transported in blood vessel P of a cigarette
smoker is usually lower than the one in the healthy individual. Explain
why does this occur?
____________________________________________________________
____________________________________________________________
____________________________________________________________
[ 2 marks ]
(d) Describe how gaseous exchange occurs between alveolus and blood
capillaries.
____________________________________________________________
____________________________________________________________
____________________________________________________________
[ 3 marks ]
3. Diagram 3 shows the gaseous exchange of oxygen and carbon dioxide between
the lungs and surrounding blood capillaries.
W X W
W
V W
Y
Z
Diagram 3
Name V, W, X, Y and Z shown in diagram 3. [ 5 marks ]
V : _________________________________
W: _________________________________
X : _________________________________
Y : _________________________________
Z : _________________________________