2 End-of-chapter test - Macmillan Academy

2 End-of-chapter test
1 The diagram below shows part of the cell surface (plasma) membrane.
B
D
E
A
C
a Identify the structures labelled A, B, C, D and E. [5]
b State one function of the structure labelled C. [1]
c Cell membranes are said to have a fluid mosaic structure.
Explain the meaning of fluid mosaic. [2]
d Some of the fatty-acid tails of the phospholipids in the membrane are saturated,
while others are unsaturated. What effect does the proportion of unsaturated fattyacid
tails have on the properties of the membrane [1]
e State two functions of membrane glycoproteins. [2]
2 Copy and complete the following account about cell signalling.
There are three main ways that receptors in the cell membrane are involved in cell signalling.
The receptor may form an ion channel. For example, the transmitter substance acetylcholine is
released by nerve cells at a ________________. At the membrane of the next nerve cell, it binds
to a receptor and causes ________________ ions to flood into the second cell, starting a new
nerve impulse.
A second mechanism is when the receptor itself acts as an enzyme. For example, the hormone
________________ binds with the enzyme tyrosine kinase, causing glucose to be changed into
________________ in liver cells.
A third mechanism involves a substance in the membrane called a ________________.
When this is activated, it triggers a series of reactions. The hormone adrenaline is
detected by liver cells in this way, causing the conversion of ________________
into glucose. [6]
3 a Explain the meaning of the term diffusion. [2]
b Polar molecules such as glucose can cross membranes by facilitated diffusion.
What are the differences between this mechanism and ordinary diffusion [2]
4 In relation to plant cells, explain the meaning of the following terms:
a osmosis
b pressure potential
c turgid
d plasmolysis. [4]
COAS Biology 1 Teacher Resources Original material © Cambridge University Press 2008 1

2 End-of-chapter test
5 What would happen if a plant cell with a water potential of –300 kPa were placed in the
following:
a distilled water
b a sucrose solution with a water potential of –2000 kPa.
Explain your answers. [4]
6 Three test tubes were labelled A, B and C. 10 cm 3 of distilled water was placed in tube A;
10 cm 3 of a 0.85% salt solution was placed in tube B; 10 cm 3 of a 2% salt solution was placed
in tube C. 1 cm 3 of fresh blood was then added to each of the tubes. The contents of the tubes
were shaken and spun in a centrifuge for 5 minutes to separate any blood cells from the
solutions. The results are shown in the diagram below.
a Explain the appearance of the contents of tube A after centrifuging. [3]
b Blood plasma has a salt concentration of about 0.85%. If you were to look through a
microscope at red blood cells taken from the precipitates in tubes B and C, describe how
they would differ in appearance. [2]
c Patients who have suffered severe burns lose fluid through the damaged skin. To treat this,
patients can be given transfusions of isotonic saline solution through a drip.
i Explain the meaning of isotonic saline solution. [1]
ii Explain why it is important that the solution is isotonic. [2]
7 Describe one similarity and two differences between facilitated diffusion and
active transport. [3]
8 Digestive enzymes are secreted from the cells of the pancreas by exocytosis.
Describe this process. [3]
9 A pea plant was grown in a sample of soil. The concentration of nitrate ions (NO 3 – ) in the soil
water was measured, and found to be 2 mmol dm –3 . The concentration of nitrate ions inside a
root cell of the pea plant was 29 mmol dm –3 . The inside of the root cell was also found to be
negatively charged compared with the outside of the cell. State the most likely mechanism that
would account for the uptake of nitrate ions by the plant, giving two reasons for your answer. [3]
Total:
46
Score: %
Grade boundaries: 80% A, 70% B, 60% C, 50% D, 40% E
COAS Biology 1 Teacher Resources Original material © Cambridge University Press 2008 2