Civics Group Index Number Name (use BLOCK LETTERS)

ST. ANDREW’S JUNIOR COLLEGE2008 JC1 Common Test

H2 BIOLOGY 9747/2

Paper 2: Core

Thursday 26 Jun 2008 2 hours

Additional Materials: Answer PaperCover Sheet for Section B

INSTRUCTIONS TO CANDIDATES

Do not open this booklet until you are told to do so.

Write your name, civics group and index number on all the work you hand in.Write in dark blue or black pen.You may use a soft pencil for any diagram, graph or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.

Section A (Structured Questions)Answer all seven questions.Write your answers in the spaces provided on the question paper.

Section B (Essay Questions)Choose one of the two questions.Write your answers on the separate answer paper provided.All working for numerical answers must be shown.

INFORMATION TO CANDIDATES

At the end of the examination,1. Attach Section B answers to the cover sheet provided.2. Enter the number of the Section B questions you have answered on the

cover sheet.

The number of marks is given in brackets [ ] at the end of each question or part question.

For Examiner’s Use

Section A

1/15

2/10

3/10

4/13

5/10

6/10

7/12

Total/80

This document consists of 21 printed pages.[Turn over

2

Section A

Answer all questions.

1 Peptic cells from the lining of mammalian stomach secrete the enzyme precursor pepsinogen. Some of these cells were isolated and maintained in a culture solution containing radioactively labeled amino acids. Samples of the cells were taken at regular intervals and prepared for electron microscopy. The following figure shows a drawing from an electron micrograph of a peptic cell. The time taken, in minutes, for radioactivity to be detected in the various cell organelles viewed under the electron microscope is shown on the right of the drawing.

(a) (i) Name the organelles labeled A to D.

A ………………………………………………………………………………………………..

B ………………………………………………………………………………………………..

C ………………………………………………………………………………………………..

D …………………………………………………………………………………………….[2]

(ii) Explain the detection at different times in the organelles labeled B and D.

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SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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(iii) Describe how the material in the organelles labeled A passes out of the cell.

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(iv) Explain why large numbers of the organelle labeled E are required in cells synthesizing and secreting proteins.

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Cells can alter the lipid composition of their membranes as an adjustment to changing temperature. For example, in winter wheat, the ratio of unsaturated phospholipids to saturated phospholipids begins to change during autumn.

(b) (i) State how the ratio of unsaturated phospholipids to saturated phospholipids will change during autumn.

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(ii) Explain how this change of ratio is advantageous for winter wheat.

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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(c) Cholesterol is a lipid found in the cell membranes of all animal tissues. It is either synthesized in the endoplasmic reticulum, or derived from the diet, in which case it is delivered by the bloodstream in low-density lipoproteins. The following figure shows the location and structure of cholesterol.

(i) With reference to membrane structure, suggest how cholesterol is held in the membrane.

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(ii) Explain the importance of cholesterol in cell membranes.

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[Q1 Total: 15]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

hydroxyl group

steroid ring

6

2 Thermus aquaticus is a bacteria which thrives in hot springs. A serine protease found in these bacteria is found to have two disulphide bonds at amino acids positions Cys69-Cys99 and Cys163-194. Three mutants of this serine protease were prepared in which the disulphide bonds Cys69-Cys99, Cys163-Cys194 and both of these disulphide bonds, respectively, were disrupted by replacing Cys residues with

Ser residues.

The table below summarises the results of the experiment when enzyme activity and stability for the wild type and 3 mutant serine proteases were investigated.

Serine Protease

Disulphide bondCys69-Cys99

Disulphide bondCys163-Cys194

Enzyme activity at 40°C / %

Time taken for half of total enzyme to

denature at 90°C / minWild type No change No change 100 45Mutant 1 Disrupted No change 68 40Mutant 2 No change Disrupted 6 10Mutant 3 Disrupted Disrupted 3 10

(a) (i) Explain why disulphide bonds are disrupted when the 2 two cysteine residues are replaced with two serine residues in amino acid at positions 69 and 99 of the polypeptide chain?

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(ii) With reference to the table above, explain which disulphide bond is more important for catalytic activity and conformational stability of the serine protease in Thermus aquaticus?

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Collagen is the main structural protein in the human body. It strengthens the tendons and supports the skin and internal organs. Bones and teeth are made by adding mineral crystals to collagen. Collagen molecules are composed of three polypeptide chains, wound together in a tight triple helix.

(b) (i) Explain why collagen is described as a fibrous protein.

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(ii) Name the types of bonds in the collagen molecule that hold together:

the primary structure;

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the secondary structure;

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(iii) Describe the main features of collagen that contribute to its tensile strength.

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SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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[Q2 Total: 10]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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3 The figure below shows the effect of increasing sucrose concentration on the activity of sucrase. The rate was determined by measuring the amount of reducing sugar produced in 15 minutes using a fixed amount of the enzyme.

(a) Explain the effect of increasing sucrose concentration on rate of reaction in terms of enzyme action

(i) between 0 and 0.6 mol dm-3 sucrose concentration.

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(ii) Between 0.6 and 0.8 mol dm-3 concentration.

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(iii) Above 0.8 mol dm-3 sucrose concentration.

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SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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A strain of the bacterium, Streptococcus pneumoniae, has been found. This strain does not grow in the presence of the antibiotic vancomycin, but neither does it die. This vancomycin tolerance is caused by a mutation of a gene coding for an enzyme G.

(b) Explain briefly how a mutation of a gene coding for the enzyme G:

(i) may still result in the production of a functional enzyme.

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(ii) may result in an enzyme with reduced activity.

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SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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[Q3 Total: 10]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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4 The graph below shows how the amount of DNA per cell of Chrysanthemum makinoi varies during periods A to E in the cell cycle

(a) (i) Radioactive thymine was supplied to the cells of some growing Chrysanthemum tissue. With reference to the graph, during which period (A to E) of the cell cycle does radioactivity of the nuclei first increase? Explain your answer.

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(ii) At anaphase of mitosis, sister chromatids separate to become individual chromosomes. Identify the period (A to E) during which anaphase occurs. Explain your answer.

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SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

A B C

D

E

13

The figure below shows the chromosomes from a cell of another plant species during anaphase I.

(b) (i) State the haploid chromosome number of this species.

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(ii) At the time shown in the figure, this cell contained 8 picograms of DNA. How much DNA would be present in each gamete produced from this cell?

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(iii) Explain why haploid cells need to be produced during a life cycle which includes sexual reproduction and state what would happen otherwise.

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SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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(c) Using the table below, distinguish between chromatids and chromosomes.

Chromatids Chromosomes

[2]

(d) Outline the sources of genetic variation in a sexually reproducing population of organisms.

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[Q4 Total: 13]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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5Step 1: During research into the mechanism of DNA replication, bacteria were grown for many generations in a medium containing only the ‘heavy’ isotope of nitrogen, 15N. This resulted in all the DNA molecules containing only 15N. This is illustrated in the figure below.

Step 2: These bacteria were then grown in a medium containing only “light’ nitrogen, 14N. After the time taken for the DNA to replicate once, the DNA was analysed.

Step 3: The bacteria continued to grow in the ‘light’ nitrogen, 14N, medium until the DNA had replicated once more. The DNA molecules were then analysed.

Step 4: The bacteria was allowed to grow in the ‘light’ nitrogen, 14N, medium for another round of DNA replication.

(a) (i) Complete the bar chart below to indicate the expected results of the composition of these DNA molecules after Step 4.

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

% D

NA

mo

lecu

les

0

75

50

25

100

DNA containing 14 N only DNA containing 14 N/15N DNA containing 15 N only

% D

NA

mo

lecu

les

0

75

50

25

100

DNA containing 14 N only DNA containing 14 N/15N DNA containing 15 N only

16

[2]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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The following shows simple diagrams of DNA molecules, indicating the nitrogen content of each.

(ii) With reference to the above diagrams, select the letter or letters which best represent the resulting bacterial DNA from Step 2 and 3.

Step 2 ...…………………………………………………………………………….

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Step 3 .……………………………………………………………………………….……....

[1]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

18

The figure below illustrates the binding of an enzyme to a DNA double helix during DNA replication.

(b) (i) Explain how the binding of this enzyme to the double helix cause changes to both their original structures.

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(ii) Both regions X and Y are helical in nature, yet they are different in their structural makeup. Briefly explain this statement.

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SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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On a planet in a distant galaxy, the organisms have evolved such that they have 6 rather than 4 different bases in their DNA, with a base composition: 24.5% U, 19% V, 25.2% W, 7.4% X, 18.8% Y and 7% Z; and they have 30 naturally occurring amino acids instead of 20.

(c) (i) With reference to the information given above, deduce the DNA structure of the extra-galactic organisms.

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(ii) State, with a reason, the minimum number of nucleotides that code for an amino acid.

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[Q5 Total: 10]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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6 The figure below shows the structure of influenza virus. Influenza virus is a member of the Orthomyxoviridae family of viruses and comprise two genera: influenza A and B viruses, and influenza C virus. Influenza A, B and C viruses are distinguished on the basis of their internal nucleoprotein and matrix proteins which are specific for each viral type.

(a) State the nature of the genetic material found in the influenza virus.

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(b) Name structure P and Q. Explain their roles in the success of influenza virus life cycle.

Structure P …………………..

Role…………………………………………………………….…………………………….…

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Structure Q …………………..

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SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

Q

P

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(c) The highly pathogenic avian flu subtype H5N1 is currently the world’s largest pandemic threat. Billions of dollars are being pumped into the research of H5N1 and other subtypes in preparation for an imminent influenza pandemic. New vaccines need to be created constantly to combat these viruses. Explain why this is so.

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(d) Describe the two different mechanisms by which enveloped viruses penetrate host cells.

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[Q6 Total: 10]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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7 The figure below is an electron micrograph of an organism isolated from the gut of a human.

(a) (i) With reference to the figure, state 2 distinguishing features which show that this organism is a bacterium.

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(ii) Using the table below, state 2 structural differences between the chromosome of a bacterium and a human cell.

Bacterium Human cell

[2]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

PromoterOperator Structural genes

lacIP lacZ lacY lacA

Promoter

Time

Am

ount o

f -ga

lactosidase

All glucose utilized

0

24

A study of the bacterium’s chromosome showed that it possessed a lac operon to allow the bacterium to metabolise lactose. The structure of the lac operon is shown below:

(b) Bacterium is grown on a medium of lactose and glucose. On the axes below, draw a graph showing how the amount of -galactosidase in the bacterium is affected after all glucose has been utilized.

[2]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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The graph below shows the growth of bacteria in the presence of glucose and lactose.

(c) Describe and explain the three parts of graph C.

Part I:

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Part II:

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Part III:

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SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

Cell count /%

Concentration/ M

Time/ min

A

B

C

Legend for graphs:

A = lactose

B = glucose

C = bacteria

Part I II III

26

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[Q7 Total: 12]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008

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Section B

Answer one of the questions.

Your answers should be illustrated by large, clearly labelled diagrams, where appropriate.

Your answers must be in continuous prose, where appropriate.

Your answers must be set out in sections (a), (b) etc., as indicated in the question.

8 (a) Compare and contrast DNA and RNA. [8]

(b) Describe how the information on mRNA is used to synthesize functional polypeptides. [12]

[Total: 20]

9 (a) Describe in detail the lysogenic life cycle of a bacteriophage using a named example. [10]

(b) Name the enzymes found in HIV and explain their importance in the replication of the virus. [5]

(c) Explain how viruses damage host cells. [5]

[Total: 20]

SAJC/9747 H2 Biology Paper 2 (Core) Jc1 H2 Common Test 2008