6. Liposomes are spherical structures composed of phospholipids. They can be made by adding phospholipids to water. Liposomes can be used to study membrane permeability.     The diagram shows a liposome.     Right-click on the blue button to open Fig 6.1        

5.2 The diagram shows the structure of thymine and four other bases, P, Q, R and S. Bases P and S can form three hydrogen bonds each and bases Q and R can form two hydrogen bonds each.     Explain which of the four bases P, Q, R or S is adenine. (2)   Right-click on the blue button to open Fig 5.2        

2.1.1 Using the information in the graph, state which of the vessels A and B is an artery and which is a vein.   Vessel A…… Vessel B ………. (1)

6.2.3 The phospholipid bilayer plays an important role in this control of movement of molecules. Explain why the phospholipid molecules form a bilayer. (3)

2. The walls of arteries and veins include endothelium, smooth muscle tissue and elastic tissue. The graph below shows the relative thickness of these tissues in the walls of two blood vessels with a similar diameter.     Right-click on the blue button to open Figure 2.1        

2.3 Warfarin is an anticoagulant drug that can be used to treat cardiovascular disease (CVD).    2.3.1 Explain the benefits of warfarin in the treatment of CVD. (3)

4.2 Explain the appearance of the red blood cells in solution B. (3)

INSTRUCTIONS   1. Answer all questions.   2. Show all the steps in any calculations and state the units.   3 The total mark for this paper is 80.   4 The marks for each question are shown in brackets – use this as a guide as to how much time to spend on each question.   5 Read each question carefully before you start to answer it.   6 Write your answers neatly and in good English and Biological terminology.   7 Try to answer every question.   8 Check your answers if you have time in the end.   9 Make sure all the work is your own.   10 Make sure of your spelling and clarity of expression in the structured questions.  

  TOTAL QUESTION 5

5.5 The DNA of an organism carries its genetic code. The diagram below shows part of the DNA of a gene.   C C A T T C                 Choose the correct answer indicating the mRNA produced from this DNA. (1)