CIE iGCSE Co-Ordinated Science B3.1 Diffusion Exam Style Questions Paper 3
Question
(a) Fig. 10.1 is a diagram representing the concentration of oxygen molecules outside and inside a cell.
(i) On Fig. 10.1, draw one arrow to represent the net movement of oxygen molecules.
(ii) State the name of the part labelled X in Fig. 10.1.
(iii) Describe one similarity and one difference between diffusion and osmosis.
similarity …………………………………………………………………………
difference …………………………………………………………
(b) Aerobic respiration requires oxygen and releases energy.
(i) State the two products of aerobic respiration.
1 ………………………………………………………………………….
2 …………………………………………………………………………
(ii) Complete these uses of energy in the body of humans.
• ………………………………… contraction
• protein …………………………………
• ………………………………… division
▶️Answer/Explanation
Ans : 10(a)(i) arrow drawn from left to right ;
10(a)(ii) cell membrane ;
10(a)(iii) similarity:
. both involve random movement of particles / movement is down a concentration gradient ;
difference:
. osmosis is the movement of water (only) / osmosis (only) occurs across partially permeable membrane ;
10(b)(i) carbon dioxide ;
water ;
10(b)(ii) muscle ;
synthesis ;
cell ;
Question
(a) Scientists investigate diffusion by measuring the distance travelled by two different dyes X and Y. They place the dyes on agar plates and measure the distance travelled every 15 seconds. Fig. 4.1 shows the results plotted on a graph. (Sub-topic – B3.1)
(i) Describe the general trend shown by both dyes in Fig. 4.1.
▶️Answer/Explanation
The general trend shown by both dyes is that the distance travelled increases with time. This indicates that diffusion is occurring, and the dyes are spreading out from their original position over time.
(ii) The dyes move through the agar by diffusion. The scientists calculate the average rate of diffusion for dye X after 30 seconds as:
\[ \frac{\text{distance travelled}}{\text{time taken}} = \frac{11}{30} = 0.37 \, \text{mm/s} \]
Calculate the average rate of diffusion for dye Y after 30 seconds.
▶️Answer/Explanation
From the graph, the distance travelled by dye Y after 30 seconds is 6 mm. Therefore, the average rate of diffusion for dye Y is:
\[ \frac{6 \, \text{mm}}{30 \, \text{s}} = 0.2 \, \text{mm/s} \]
(b) Describe the direction of motion of particles during diffusion. (Sub-topic – B3.1)
▶️Answer/Explanation
During diffusion, particles move from a region of higher concentration to a region of lower concentration. This movement occurs due to the random motion of particles, and it continues until the concentration of particles is uniform throughout the medium.
(c) Substances move into and out of cells by diffusion. (Sub-topic – B3.1)
(i) State the part of the cell that controls the movement of substances in and out of the cell.
▶️Answer/Explanation
The cell membrane controls the movement of substances in and out of the cell.
(ii) Circle two substances that diffuse into cells for respiration.
carbon dioxide fatty acids glucose oxygen starch water
▶️Answer/Explanation
The two substances that diffuse into cells for respiration are glucose and oxygen.
(d) Table 4.1 shows some components of plant cells and their function. Complete Table 4.1.
| Component of Plant Cell | Function |
|---|---|
| Vacuole | Contains cell sap to support the plant cell |
| Cytoplasm | Where chemical reactions occur / contains the cell structures / contains enzymes |
| Chloroplast | Where photosynthesis occurs |
▶️Answer/Explanation
The completed table is as follows:
| Component of Plant Cell | Function |
|---|---|
| Vacuole | Contains cell sap to support the plant cell |
| Cytoplasm | Where chemical reactions occur / contains the cell structures / contains enzymes |
| Chloroplast | Where photosynthesis occurs |