2015_human_biology_unit_1_marking_guide - for moodle!!.docx - HUMAN BIOLOGY Unit 1 2015 Marking Guide 2 2015 Human Biology Unit 1 Marking Guide Section

2015_human_biology_unit_1_marking_guide - for moodle!!.docx...

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Marking Guide HUMAN BIOLOGY Unit 1 2015
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2 2015 Human Biology Unit 1 Marking Guide Section One: Multiple-choice 30% (60 Marks) 1 C 2 C 3 B 4 A 5 A 6 D 7 C 8 C 9 A 10 C 11 A 12 C 13 A 14 A 15 A 16 C 17 B 18 D 19 C 20 C 21 A 22 B 23 A 24 B 25 D 26 A 27 D 28 C 29 D 30 C
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2015 Human Biology Unit 1 Marking Guide 3 Section Two: Short answer 50% (100 Marks) Question 31 (13 marks) (a) (i) Draw a diagram on an erythrocyte. (1 mark) need to draw biconcave surface/ no nucleus (ii) Explain two ways in which the structure of an erythrocyte is well suited to its function. Description Marks No nucleus – more space for haemoglobin 1 Biconcave disc increases surface area allowing more rapid exchange of gases across the surface 1 (b) Describe the main function of: (i) leucocytes: Description (any 1 of the following) Marks Remove dead/ injured cells/ pathogens 1 (ii) plasma proteins: Description (any 1 of the following) Marks blood clotting 1 Antibodies – immune response 1 Alter osmotic pressure of blood 1
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4 2015 Human Biology Unit 1 Marking Guide (c) Explain why it would be a problem for your body if the water levels of plasma increased to 95%. Description (any 2 of the following) Marks It would change the concentration gradient between the cells and plasma 1 Too much water would leave the plasma and enter body cells 1 Result in lysis of cells/ organ failure 1 (d) How does the composition of lymph differ from that of blood (as shown in the table)? Description Marks It lacks the presence of formed elements /WBC/ RBC/ Platelets/ 1 (e) Describe TWO functions of the lymphatic system. Description Marks Return excess fluid from body tissues to blood 1 Lymph nodes involved in the body’s immune response/ filtering lymph 1 (f) Explain why it is important that blood type is known before receiving a blood transfusion. In your answer include what happens when blood types are mixed. Description (any 3) Marks When this happens it results in agglutination of RBC which blocks capillaries and result in death (must have) 1 RBC have an antigen present on its surface (A/ B/ AB/ None) 1 Plasma has antibodies present which can bind to an antigen (anti A to antigen A etc) 1 Therefore need to ensure transfusion does not contain the complementary antibody to the person’s RBC antigens 1
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2015 Human Biology Unit 1 Marking Guide 5 Question 32 (19 marks) (a) (i) State the function of the following structures: Description Marks C – involved in mitosis and meiosis/ cell division / form spindles to which chromosomes attach 1 D –controls all protein production by the cell/ control centre of the cell 1 L – provides a surface for chemical reactions/ channels transport or store materials 1 (b) Describe how proteins are arranged in a plasma membrane and the part they play in transporting substances into and out of cells. Description Marks They are embedded in the phospholipid bilayer on either surface (must have) 1 pass from one side to the other (must have) 1 Channel proteins allow the movement of ions and water 1 By diffusion/ passively/ without the use of energy 1
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