MidYearPaper2~Question 3 ~seseri

Diagram 3.1 shows the gaseous exchange system in an insect and respiratory structure of a unicellular organism such as Amoeba.

(a) i. Name the structures labelled P and R.[2 marks]
ii. What is the function of structure Q? [1 mark]
(b) i. State the substance that forms the ring at structure R. [1 mark]
ii. State the role of the ring. [1 mark]

(c) i. At the end of structure S, there is a type of substance that helps in gaseous exchange.
What is the substance? [ 1 mark ]
ii. Describe how this substance helps in the process of gaseous exchange in cells. [2 m ]
(d) Explain respiration in an unicellar organism such as the Amoeba and what makes
the process highly efficient? [ 4 m ]

Suggested Answer:

(a) (i) P : Spiracle
R : Trachea
(ii) Q controls the opening and closing of the spiracles

(b)(i) Chitin
(ii) To prevent the air tubes from collapsing

(c)(i) Tracheole fluid / fluid
(ii) P1 - Respiratory gases can dissolve in the fluid
P2 - before it diffuses into the body cells

(d) P1 - Concentration of oxygen is higher in the outside
environment compared to inside of cell
P2 - Oxygen diffuses into the cell by diffusion across the
plasma membrane
P3 - Concentration of carbon dioxide is higher in the
amoeba compared to the outside environment
P4 - Carbon dioxide diffuses out through the plasma
membrane by diffusion
P5 - Amoeba has a relatively large surface area as compared
to the volume of its body for diffusion of gases
P6 - Its plasma membrane is thin and

P7-constantly moist for rapid diffusion of gases.......................ANY 4 points..