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 (Bio, Hbio)
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
[Total 15 marks]

3.	(a)	(i)	A = glycerol	1
	B = fatty acid (residue)	1
(ii)	hydrolysis	1
(b)	polar (molecules) / hydrophilic heads/eq & hydrophobic tails/eq	1
form a bilayer / bimolecular double layer 
[accept from clear diagram]	1
(polar/hydrophilic) heads outside / (non–polar/hydrophobic) tails inside	1
[6]

4.	(a)	A	phospholipid ;
B	protein ;
C	glycoprotein ;	3
(b)	act as a marker / antigen / recognition site ;
other molecules combine with it / detecting similar / non-self cells ;
OR
reference to receptor / binding site ;
other (specific) molecules / named e.g. / combine with it ;	2
[5]

5.	(a)	Phospholipid ;	1
(b)	A	Glycerol / propan 1,2,3 triol ;
B	Ester bond / ester linkage ;	2
(c)	Insoluble in water / does not dissolve in water / non-polar ;	1
(d)	(Fluid because) phospholipids move (around membrane) ;
	(Mosaic because) membrane contains proteins /
glycoproteins (lying amongst phospholipids) / eq ;	2
[6]

6.	(a)	{Fatty acid / tails} are {hydrophobic / non-polar} ;
(so orientate themselves) away from {water / polar environment} ;
{Phosphate / heads} are {hydrophilic / polar} ;
(so can) interact with {water / polar environment} ;	3
(b)	Correct measurement ;   [27 mm or 37 / 38 mm]
Divide by magnification  ;
Correct conversion to mm ;   [answer = 0.009 or 0.012 / 0.013]	3
(c)	Carbohydrate: Cell recognition / cell adhesion / eq ;	1
	Protein: Transport of molecules / eq OR
receptor for hormone / eq OR enzymes ;	1
[8]

7.	Accept points only in correct context
	1.	phospholipid bilayer ;
2.	polar / phosphate / hydrophilic (groups of phospholipids) face outwards ;
3.	nonpolar / hydrophobic / fatty acid tails face inwards ;
4.	reference to cholesterol ;
5.	molecules can move around ;
6.	proteins present in membrane ;
7.	qualification of the location of these proteins ;
8.	glycosidic / carbohydrate side chains on lipids / proteins / glycolipids / 
	glycoproteins / glycocalyx ;
9.	involvement of proteins in transport (across membrane) ;
10.	by active transport / facilitated diffusion described (e.g. reference to 
	attachment / change in shape) ;
11.	some proteins are enzymes ;
12.	partially / selectively permeable / eq ;
13.	reference to cell-cell interaction / recognition / antigens ;
14.	reference to receptors for hormones / neurotransmitters ;
15.	vesicle fusion / formation / description of membrane involvement in
	exo- or endo-cytosis ;
[10]