1.	The table below refers to components of the cell surface membrane (plasma membrane) and to their roles in transporting substances across the membrane.
Complete the table by inserting an appropriate word or words in the empty boxes.

(Total 6 marks)

2.	Write an essay on the following topic:
	The structure and functions of cell surface membranes.
(15)
structure and function of cell surface membranes:
Introduction could include:
outline of fluid mosaic model -
communication with external medium, barrier -
controls exchange of material -
fluid mosaic model:
phospholipids and orientation -
proteins, glycocalyx, channels -
microvilli -
passage through the membrane:
diffusion, facilitated diffusion, Na/K -
osmosis, active transport, ATPase -
lipid soluble molecules, adrenaline 
polar molecules through pores, channels -
Vesicles:
cytosis -
endocytosis, phagocytosis, pinocytosis -
exocytosis, secretory vesicles others:
glycosides as receptors, insulin-
adhesion between cells -
immunological response S = 13, B = 2,C = 2

3.	The diagram below shows the general structure of a phospholipid.

(a)	(i)	Name the parts labelled A and B.
A	................................................................................................................
B	................................................................................................................
(2)
(ii)	Name the type of reaction by which the bonds between parts A and B may be broken.
...………………………………………………………………………………
(1)
(b)	Phospholipids are major components of cell membranes.  Explain how the properties of phospholipids are important in membrane formation.
...…………………………………………………………………………………....
...…………………………………………………………………………………....
...…………………………………………………………………………………....
...…………………………………………………………………………………....
(3)
(Total 6 marks)

4.	The diagram below represents the structure of part of the cell surface membrane.

(a)	Name the molecules labelled A, B and C.
A …………………………………………………………………………………….
B …………………………………………………………………………………….
C …………………………………………………………………………………….
(3)
(b)	Describe one function of part C.
……………………………………………………………………………………….
……………………………………………………………………………………….
……………………………………………………………………………………….
……………………………………………………………………………………….
(2)
(Total 5 marks)

5.	The diagram below shows the structure of a molecule found in the cell surface membrane.

(a)	Name the type of molecule shown in the diagram.
.....................................................................................................................................
(1)
(b)	Name A and B as labelled on the diagram.
A .................................................................................................................................
B .................................................................................................................................
(2)
(c)	Region X is said to be hydrophobic.  What is meant by the term hydrophobic? 
.....................................................................................................................................
.....................................................................................................................................
(1)
(d)	Explain why the cell surface membrane is described as a fluid-mosaic.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 6 marks)

6.	The diagram below shows the structure of the cell surface membrane.

(a)	The cell surface membrane is composed of a phospholipid bilayer. Explain why tile phospholipids in the bilayer are arranged with the fatty acid tails pointing inwards and the phosphate heads outwards.
……………………………………………….………………………………………
……………………………………………….………………………………………
……………………………………………….………………………………………
……………………………………………….………………………………………
……………………………………………….………………………………………
……………………………………………….………………………………………
(3)
(b)	The diagram has been magnified three million (3 × 106) times. Calculate the width of the cell surface membrane in tin (micrometres). Show your working.

Answer ………………………… mm
(3)
(c)	State one function of each of the following components of the cell surface membrane.
Carbohydrate ………………………………………………………………………..
Protein ………………………………………………………………………………
(2)
(Total 8 marks)

7.	Give an account of the structure and functions of the cell surface membrane.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
	(Allow three lined pages)
(Total 10 marks)