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Papa Refmnce (comple4e below)
Candidate Signature
6101101
EEde
xcemBiology
Biology (Human)
Advanced SubsidiaryIAdvanced
Unit Test 1
Thursday 10 January 2002 - Afternoon
Time: 1 hour 20 minutes
Materials required for examination Iterns includedwith question papers
Ruler Nil
Instructi~nsto Candidates
Eixamina'suse only
Tcam Leader's use only
In the boxes above, write your centre number, candidate number, the paper reference,your signature, surname and initials. The paper reference is shown above. Check that youhave the booklet for the correct unit.Answer ALL NINE questions in the spaces provided in this booklet.Your answer to Question 9 should be written on the lined pages. If you need to useadditional answer sheets, attach them loosely but securely inside this booklet.Show a l l the steps in any calculations and state the units. Calculators may be used.Include diagrams in your answers where these are helpful.
Information for Candidates
The marks for individual questions and parts of questions are shown in round brackets:e.g. (2).The total mark for this question paper is 70.
Advice to Candidates
You will be assessed on your ability to organise and ptesent information, ideas,descriptions and arguments clearly and logically, taking account of your use of grammar,punctuation and spelling.
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Answer ALL questions in the spaces provided
1. The table below refers to features of prokaryotic and eukaryoticcells. If the feature isusually present, place a tick ( J )in the appropriate box and if the feature is absent, placea cross ( I ( ) in the appropriate box.
(Total 4 marks)
Feature
Cell surface membrane
Plasmids
Ribosomes
Mitochondria
2. Read through the following passage about protein structure, then write on the dottedlines the most appropriate word or words to complete the passage.
Proteins are composed of long chains of monomers called ..............................................which are linked together by ............................................... bonds. These bonds are
formed by ................................................ reactions between adjacent monomers. The
Prokaryotic cell
primary structure of a protein is the specific sequence of monomers in a polypeptide
chain and determines the secondary and tertiary protein structure. The secondary/
structure of a protein may be a coil, known as an .................................................which is held in shape by ................................................ bonds between different
monomers in the chain.
Eukaryotic cell
(Total 5 marks)
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Q1
7
Q2
7
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Explain what is meant by the term diffusion.
....................................................................................................................................
(2)
State two factors which influence the rate of diffusion across a cell surfacemembrane.
Give one way in which active transport differs from diffusion.
(Total 5 marks)
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4. Describe the role of messenger RNA (mRNA) in the following processes.
(a) Transcription
....................................................................................................................................
(b) Translation
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(a) Give two features that help to identify this as an animal cell.
The drawing below shows an animal cell, magnified X 1000, undergoing mitosis.
(2)
Name the parts labelled A and B.
B ................................................................................................................................(2)
Name the stage of mitosis shown in the drawing.
..............................A....................................................................................................(1)
Calculate the actual maximum diameter of this cell. Show your working.
.....................................................Answer
(2)
(Total 7 marks1
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6. The graph below shows the results of..an investigation into the effect of substrateconcentration on the initial rate of an enzymecontrolled reaction.
Initial 0.15rate of reactionlmg of product S-'
0.10
Substrate concentrationlmgcm-3
(a) Suggest two conditions, apart from temperature, that should be kept constant inthis investigation.
2 .................................................................................................................................(21
(b) Explain why changes in the substrate concentration cause an increase in the rate of reaction between points A and B on the graph.
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(c) ,Suggest why the curve levels off between points B and C.
....................................................................................................................................
(2)
(d) On the graph on page 6, sketch a curve to show how the results for theinvestigation would change if it were repeated at a lower temperature.
Explain any differences between the two curves.
(Total 9marks)
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7. A procedure was carriedout to separatehe major organelles within liver cells. Thisinvolved breaking up (homogenising) liver tissue in an icecold salt solution which hadthe same water potential as the cell cytoplasm.
Ultracentrifugation was then used to separate the organelles. Ultracentrifugation is aprocess that separates materials of different densities by spinning them in a tube at
different speeds. The denser materialsare forced to the bottom of the tube as a pellet,while less dense materials remain nearer to the top of the tube in liquid known as the
supematant.
The flow chart below summarises the steps involved in this procedure.
Liver tissue broken upin icecold salt solution
Supernatant centrifuged at medium- speed for 20 minutes
Centrifuged at low speed for10 minutes
Supernatant centrifuged at highspeed for 30 minutes
Final supernatant
+
(a) Suggest why it was necessary for the salt solution to have the same water potentialas the cell cytoplasm.
Pellet A
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(b) This procedure separated mitochondria, nuclei and ribosomes into the three pellets,A, B and C. Complete the table below to show which one of these organelles
would be found in which pellet.
(c) Suggest twocomponents of the cell,other than water, that might be present in thefinal supernatant.
2 .................................................................................................................................(2)
(d) In the space below, draw and label a diagram to show the structure of a
mitochondrion.
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(e) Explain why large numbers of mitochondria are found in liver cells.
(Total 12 marks)
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8. The diagram below shows the structure of a nucleotide.
(a) Identify the parts labelled A. B and C in the diagram.
(b) The sequence of bases from part of a gene is shown below.
A G C C G T C C C G T C
Write out the sequence of bases on messenger RNA (rnRNA) that would be coded
for by this part of the gene.
, (c) Describe what is meant by the semianservativereplication of DNA.
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(d) A quantity of DNA was labelled with radioactive nitrogen. It was then allowed toreplicatethree times, using non-radioactive nucleotides to synthesise the new DNAstrands. What proportion of the final mass of DNA would you expect to &radioactive? Explain your answer.
....................................................................................................................................
(2)
(e) In which stage of the cell cycle does replication of DNA take place?
(Total 12 marks)
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9. Give an account of the structure and functions of the cell surface membrane.
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