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STRICTLY CONFIDENTIAL
WELSH JOINT EDUCATION COMMITTEE
CYD-BWYLLGOR ADDYSG CYMRU
MARK SCHEME
AS UNIT BI1
JUNE 2002
Chief Examiner:
Mr. B. Hughes, 31 Cowleaze, Undy, Caldicot. NP26 3LE
Telephone No: 01633 882572
Conference Date/Time:
Monday, 10 June 2002 at 10.00 a.m.
Conference Venue:
WJEC, 245 Western Avenue, Cardiff. CF5 2YX
NOTES
Assistants are asked to read and digest thoroughly all the information set out in the document
"Instructions for Examiners". It is essential for the smooth running of the examination that these
instructions are adhered to by all. Particular attention should be paid to the following instructions
regarding marking:
1.
Compliance with the mark scheme is required of all assistants in order to ensure
comparability. The mark scheme shows a variety of suitable correct answers to the questions.
Over-rigidity in its interpretation is not intended and it is accepted that points may be made in
a variety of different ways to include converse and counterpoints. Thus, except where terms
are specifically requested, all correct responses even if expressed using different words are
acceptable provided the points are explicit, unambiguous and made in the correct context.
2.
Marking is to be carried out with a red ballpoint or felt-tip pen. The ticks are to be placed on
the word or phrase which qualifies for the mark.
3.
The total for the question should be written at the end of the question.
4.
Transfer each checked total to the front cover.
5.
It is essential that all assistants mark approximately 20-30 scripts in pencil in order to try out
the mark scheme before the meeting. Any queries which you have should be raised at the
meeting.
6.
If you have any queries when marking, contact the Chief Examiner. If you have any
difficulties contact the Subject Officer (029 2026 5126). Your marking load can be reduced
or re-allocated if the need arises.
7.
Allow phonetic spelling except where there is a possibility that scientific terms might be
confused.
8.
When candidates list alternative answers mark the first answer only/the number from the
beginning which corresponds to the number of marking points.
After the meeting
As soon as possible send the Chief Examiner/Team Leader 10 marked and checked scripts, together
with a stamped addressed envelope and your telephone number. Marking may continue once these
have been checked and a reply given.
It is essential that marked scripts are returned in batches of approximately 100 throughout the
marking period. The final date for the receipt of the last batch of scripts and L forms at the WJEC is
Monday, 1 July 2002.
1
MARK SCHEME
BI1 - JUNE 2002
1.
(a)
(i)
(ii)
(iii)
(iv)
cellulose
eukaryotic
plasmid
glucose oxidase
(1)
(1)
(1)
(1)
(b)
(i)
(ii)
Phagocytosis is (intake) of solids, pinocytosis is . . . liquids
(1)
Turgid is firm/cytoplasm pressed against wall/positive p/higher water
content, plasmolysed is reverse
(1)
(comparison needed)
Total = 6 marks
2.
3.
(a)
A glycerol
B fatty acid
(1)
(1)
(b)
Ring around 2Hs and 1 O between components
(1)
(c)
Condensation
(1)
(d)
Each fatty acid joined by oxygen bridge
(1)
Double bond to C atom of each fatty acid
(1)
(e)
(i)
(ii)
Trigycerides/triacylglycerol
Energy (store)/respiratory water (not: storage)
(1)
(1)
(f)
(i)
(ii)
(iii)
Heart disease/coronary/angina
(1)
In olive oil fatty acids are unsaturated/have double bonds
(1)
Fats are solid oils are liquid (at physiological temperatures)/
(1)
reference to different melting points.
Total = 11 marks
(a)
(A substance) which speeds up the rate of a chemical reaction
(1)
(b)
Activation energy/energy required
(1)
(c)
(Increasing conc. of malonic acid) reduces the rate of reaction/increases
inhibition
(1)
(d)
Competitive
(e)
The malonic acid/inhibitor has similar structure to succinic/substrate (could be
show in diagram)
(1)
Competes with substrate for active sites/binds with active site
(1)
The more sites occupied by inhibitor the fewer there are for substrate/
(1)
decrease in enzyme - substrate complexes.
(allow consequential error if non-competitive, inhibitor binds to site other than
active site(1), changes shape of active site (1) substrate no longer fits (1)
(1)
2
(f)
Use a buffer/add acid and alkali with monitoring.
(1)
(g)
Replicate conditions/repeat experiment
Using boiled (and cooled)/denatured extract
(not: ref. to water/leave enzyme out)
(1)
(1)
Total = 10 marks
4.
(a)
(i)
(ii)
(iii)
(iv)
(v)
(vi)
A
C
B
F
E
C
(1)
(1)
(1)
(1)
(1)
(1)
(b)
(i)
(ii)
4
2
(1)
(1)
(c)
Provides haploid cells (for mixing 2 sets at fertilisation)
Random/Independent assortment shuffles chromosomes; Crossing over;
Specific reference to trisomy.
(not: random fertilisation/mutation unqualified)
(3)
Total = 11 marks
5.
6.
(a)
X = protein
Y = (phospho) lipid
Z = carbohydrate/polysaccharide/glycocalyx/glycoprotein
(1)
(1)
(1)
(b)
Double layer; heads out tails in; 2 correct labels
(3)
(c)
Labelled molecules/x/protein (1) reference to mixing or equivalent (1)
(2)
(d)
Taking up nutrients/other requirements/reference to selective permeability;
phagocytosis/secreting chemicals; cell recognition; adhesion; receptor sites.
(any 3)
(3)
(not: controlling entry and exit/protection)
Total = 11 marks
(a)
transcription
Occurs in the nucleus
/
Involves messenger RNA
/
Needs RNA polymerase
/
translation
/
Involves formation of peptide
bonds
/
Occurs in ribosomes
/
1
for
each
row
(5)
3
(b)
(i)
(ii)
TAC/GAA/TGA/CCA/GTT
Met-leu-thr-gly-glu
(1 mark if only 1 error)
(1 mark if only 1 error)
(2)
(2)
(c)
(not: triplet)
(2)
Total = 11 marks
4
7.
(a)
A
Primary is (type, number and) sequence/order of amino acids
(1)
B
linked by peptide bonds
(1)
C
Secondary is (3D) folding/most common is () helix/  pleated sheet
(1)
D
formed by hydrogen bonds (between peptide bonds)
(1)
E
Tertiary is folding/twisting of a  helix/structure
(1)
F
(As shown by) globular proteins
(1)
G
To form very specific (3D) shapes
(1)
H
R groups project from  helix/side chains/part of active site
(i.e. function of R groups)
(1)
I
And may react to form bonds which stabilise 3D shape
(i.e. side chains)
J, K
Any two from, covalent/disulphide bridges; ionic/salt bridges;
hydrogen bonds; hydrophobic bonds.
(1)
(1)
L
Quaternary is two or more polypeptide/amino acid chains.
(not: protein)
(1)
M
Joined by similar bonds between projecting R groups.
(i.e. named bond between R groups)
(1)
N
e.g. Haemoglobin.
(1)
O
Fibrous proteins have helices linked in strands.
(Maximum 10 from available 15)
(1)
Total = 10 marks
5
7.
(b)
A
Mitochondrion has double/inner and outer membrane.
(1)
B
Inter-membrane space.
(1)
C
cristae/stalked particles.
(1)
D
matrix.
(1)
E
DNA/ribosome (in either mitochondrion or chloroplast).
(1)
F
Self replicating (either mitochondrion or chloroplast).
(1)
G
The function is energy release/ATP production/aerobic respiration. (1)
H
Chloroplast has double/inner and outer membrane.
(1)
I
stroma.
(1)
J
Flattened sacs/lamellae/thylakoids.
(1)
K
(stacked to form) grana.
(1)
L
sites of photosynthetic pigments/chlorophyll
e.g. grana, thylakoids
(1)
M
Starch grains.
(1)
N
Function is photosynthesis.
(1)
O
Some attempt at genuine comparison.
(Maximum 10 from available 15)
(1)
Any 9 points plus point O.
Total = 10 marks
GCE June 2004: Biology Mark Scheme - BI1/ED
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