4
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MARGIN
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3 Differential centrifugation was used to isolate five components from leaf cells.
(a) The leaf tissue was first homogenised in ice-cold isotonic sucrose solution. Explain
why an isotonic solution was used.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(2 marks)
(b) The homogenate was then centrifuged five times, each time at a higher speed. The
pellet formed at the bottom of the centrifuge tube after each centrifugation was
removed. Each pellet contained a different cell component. The components were cell
walls, chloroplasts, mitochondria, nuclei and ribosomes.
(i) Complete the table to show the order in which the cell components were isolated
from the homogenate.
Order in which pellets were
produced
Cell component
1
2
3
Chloroplasts
4
5
(2 marks)
(ii) Which of these cell components contains the most polysaccharide?
...................................................................................................................................
(1 mark)
(iii) Which of these cell components is the site of protein synthesis?
...................................................................................................................................
(1 mark)
APW/Jan07/BYB1
5
LEAVE
MARGIN
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(c) Complete the table to give two structural differences, other than size, between a
chloroplast and a mitochondrion.
Chloroplast
Mitochondrion
(2 marks)
8
Turn over for the next question
Turn over !
APW/Jan07/BYB1
Biology B - AQA GCE Mark Scheme 2007 January series
Question 3
(a)
(b)
(c)
No net movement of water / no osmosis / no osmotic effects;
Prevent organelles / named organelle changing shape / bursting;
(reject cells and cell components)
(i)
2
1 Cell walls
2 Nuclei
4 Mitochondria
5 Ribosomes;
(any 3 in correct order = 1 mark)
(allow number if correctly corresponding to named part)
2
(ii)
(Cell) walls;
1
(iii)
Ribosomes;
1
Reference to:
Cristae/folded inner membrane/detail of structure;
Starch grains;
Grana/detail of structure;
(use list rules for marking)
(shape neutral)
(allow labelled diagrams)
2 max
Total 8
Question 4
(a)
(b)
(i)
Condensation;
1
(ii)
Box drawn around appropriate OH and H;
1
(iii)
Peptide;
1
(i)
Hydrogen/ionic;
1
(ii)
Cysteine;
Contains sulphur;
Required to form disulphide bonds / sulphide bridges / (S-S bonds);
Bonds are strong / bonds are covalent (not broken by heat treatment);
(if not cysteine, then max 1)
2 max
Total 7
4
2
Areas outside
the box will
not be scanned
for marking
Answer all questions in the spaces provided.
1 The diagram shows part of an epithelial cell from the small intestine as seen with an electron
microscope.
A
B
1
(a) What is the function of the organelles labelled A and B?
A .........................................................................................................................................
.............................................................................................................................................
B .........................................................................................................................................
.............................................................................................................................................
(2 marks)
(02)
APW/Jun09/BYB1
3
1
Areas outside
the box will
not be scanned
for marking
(b) Name one organelle shown in the diagram that would be present in a prokaryotic cell.
.............................................................................................................................................
(1 mark)
1
(c) The internal structure of organelle B can be seen using an electron microscope but not
with a light microscope. Explain why.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(2 marks)
(Extra space) ......................................................................................................................
.............................................................................................................................................
5
Turn over for the next question
Turn over !
(03)
APW/Jun09/BYB1
Biology - AQA GCE Mark Scheme 2009 June series
Question
Part
1
(a)
Sub Part
Marking Guidance
Mark
A – modifies/packages/ proteins/enzymes / produce glycoproteins /vesicles
/lysosomes;
2
Comments
B – aerobic respiration/production of ATP/converts energy;
1
(b)
Ribosome;
1
1
(c)
Electron microscope uses (a beam of) electrons;
2 max
Shorter wavelength than light;
Or description
Greater resolution;
3
4
2
Areas outside
the box will
not be scanned
for marking
(a) The table shows some features that may or may not be present in different cells.
Complete the table with either a tick if the feature is present or a cross if it is not
present.
Cell
Feature
Red blood cell
Leaf cell
Bacterium
Epithelial cell
from alveolus
Nucleus
Plasma membrane
surrounding cell
Cell wall
(4 marks)
2
(b) Some of the cells in the pancreas make large amounts of enzymes. These cells contain
many ribosomes and many mitochondria. Explain the importance of these cells
containing
2
(b)
(i) many ribosomes
...................................................................................................................................
...................................................................................................................................
(1 mark)
2
(b)
(ii) many mitochondria.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
(2 marks)
(04)
APW/Jun08/BYA1 R
Biology Specification A - AQA GCE Mark Scheme 2008 June series
Question 1
(a)
(i)
Box drawn round appropriate H and OH;
1
(ii)
Condensation;
Accept close versions such as condensing reaction or condensing.
1
(b)
An H atom is at the bottom/an OH is at the top in glucose;
At the right-hand side of the molecule;
2
Note that this is the lowest acceptable answer. Better candidates might be expected to
refer to C1. Obviously such answers should gain credit. Reject polymerisation.
(c)
Two marks for correct answer of 0.9/0.89 or expressed as fraction 8/9 / 0.8 ;;
One mark for incorrect answer such as 1.12(5) or 0.8 derived from correct values;
One mark for 0.9 with no working;
2 max
(d)
(i)
Left hand side marked;
1
(ii)
Separates amino acids/spots/B and C more;
1
.
Total
8
Question 2
(a)
Cell
Feature
Red blood cell
Nucleus
X
Plasma membrane
surrounding cell
Cell wall
X
Leaf cell
Bacterium
Epithelial cell
from alveolus
X
X
Allow one mark for each correct column;;;;
Do not accept hybrid tick/crosses or blank spaces.
If no crosses at all accept blank as equivalent to a cross
(b)
(c)
4
(i)
Site of enzyme/protein synthesis;
1
(ii)
Release/transfer/make available energy/ATP/site of respiration;
For synthesising/making/secreting proteins/enzymes;
Ignore references to making/producing energy.
2
Blue/blue-black/purple/black with iodine;
Reference to use of microscope;
2
Total
3
9
6
Areas outside
the box will
not be scanned
for marking
3 In the diagram, the circles represent three types of cell. The letters A to G represent features
found in these cells.
Prokaryotic cell
White blood cell
A
B
C
D
E
F
G
Leaf cell
3
(a) In which space A to G would you put the following?
3
(a)
(i) Nucleus
...................................................................................................................................
(1 mark)
3
(a)
(ii) Cell wall
...................................................................................................................................
(1 mark)
3
(b) Name one organelle that should be put in
3
(b)
(i) space D
...................................................................................................................................
(1 mark)
3
(b)
(ii) space G.
...................................................................................................................................
(1 mark)
(06)
APW/Jan09/BYA1
7
3
(c)
Areas outside
the box will
not be scanned
for marking
(i) Give one feature of a lysosome that could be seen with a transmission electron
microscope.
...................................................................................................................................
(1 mark)
3
(c)
(ii) The detailed structure of a lysosome can be seen with a transmission electron
microscope. It cannot be seen with an optical microscope.
Explain why the detailed structure of a lysosome cannot be seen with an optical
microscope.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
(2 marks)
3
(c) (iii) Immediately after giving birth, a woman’s uterus weighed approximately 2 kg.
As soon as the baby was born, the tissues of her uterus were invaded by white
blood cells. These white blood cells contain lysosomes. Nine days after giving
birth her uterus weighed about 50 g.
Explain the link between the lysosomes and the change in mass of the woman’s
uterus.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
(2 marks)
9
Turn over !
(07)
APW/Jan09/BYA1
Biology Specification A - AQA GCE Mark Scheme 2009 January series
Question 1
(a)
Nitrogen;
Q Do not accept N in the context of this question.
(b)
(i)
(c)
(d)
1
Heat with Benedict’s solution;
Green/yellow/orange/red (precipitate);
Q Do not accept unqualified references to placing in a water bath.
2
(ii)
A;
1
(i)
Joining together/forming a bond/with removal of (a molecule of) water;
1
(ii)
C;
1
(i)
D;
1
(ii)
Maximum amount of hydrogen;
No double bonds/all carbon atoms attached to two hydrogen atoms;
In hydrocarbon chain between carbon atoms/other than in COOH group; 2 max
Total
9
Question 2
(a)
Capillary endothelium/epithelium and alveolar epithelium;;
Capillary wall/wall of alveolus;
2
General principle for marking
One mark for correct identification of the layers involved. Two marks for correct
identification of layers involved and use of appropriate terminology.
(b)
(i)
(ii)
(c)
Contracts/lowers/flattens;
Increases volume;
2
Air entering the lungs (during inspiration);
1
Correct answer of 18.2/18.18/18;;
Incorrect answer correctly based on identifying duration of one complete breath
as 3.3 seconds;
2
Total
7
Question 3
(a)
(b)
(i)
F;
1
(ii)
E;
1
(i)
Ribosome/ Accept plasma/cell (surface) membrane;
1
(ii)
Chloroplast/ (Large) vacuole;
1
3
Biology Specification A - AQA GCE Mark Scheme 2009 January series
(c)
(i)
Membrane/Accept lumen/shape;
1
(ii)
Uses light which has longer wavelength;
Optical microscope has low(er) resolution/resolving power;
Q The term resolution is essential for the second mark.
2
(iii)
Contain/release/secrete enzymes;
Lysosomes/enzymes digest/break down/destroy proteins/cells/tissue (of uterus);
2
Total
9
Question 4
(a)
(b)
(c)
(S=) C
H;
1
(More) impulses along parasympathetic/vagus nerve/fewer/no impulses along
sympathetic/accelerator nerve;
SAN sends fewer impulses/waves if electrical activity/signals;
Q To gain first marking point, a reference must be made to impulses.
Do not credit such terms as messages.
2
(i)
0.5 (cm3 g-1 minute-1);
1
(ii)
(Allow comparison because) the organs/tissues are different sizes/
masses/weights;
1
Heart muscle contracts more/work harder/increase cardiac output;
More oxygen/respires faster/removes carbon dioxide;
2
(iii)
Total
7
Question 5
(a)
(i)
Valve J
Closes
Valve K
Opens;
1
(ii)
Increases pressure (of blood)/in vein/between valves;
Higher pressure above than below valve (opens valve);
4
2
2
Areas outside
the box will
not be scanned
for marking
Answer all questions in the spaces provided.
1 The diagram shows how some organelles may be distinguished from each other.
Organelle found in prokaryotic
and eukaryotic cells.
Organelle A
Organelle found only in
eukaryotic cells.
Organelle found in
animal cells and in
plant cells. Does not
contain membranes
arranged in stacks.
Larger organelle surrounded
by an envelope through which
there are pores. Usually one
per cell.
Organelle C
1
(a)
Organelle found in
plant cells. Contains
inner membranes
arranged in stacks.
Organelle B
Smaller organelle surrounded
by an outer membrane. Has an inner
membrane, folded to form cristae.
Many in a cell.
Organelle D
(i) Name organelle B.
...................................................................................................................................
(1 mark)
1
(a)
(ii) Describe the function of organelle B.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
(2 marks)
(02)
APW/Jun09/BYA1
3
1
(b) Which organelle A, B, C or D
1
(b)
Areas outside
the box will
not be scanned
for marking
(i) is a ribosome?
(1 mark)
1
(b)
(ii) contains most of the DNA found in a plant cell?
(1 mark)
1
(c) Some liver tissue was ground, filtered and centrifuged to make a suspension of
organelle D.
1
(c)
(i) Explain why the solution in which the liver tissue was ground should be ice-cold.
...................................................................................................................................
...................................................................................................................................
(1 mark)
1
(c)
(ii) The ground liver was centrifuged at low speed. The pellet that formed at the
bottom of the centrifuge tube was thrown away and the supernatant centrifuged
again at higher speed. Explain why it was necessary to first centrifuge the
ground liver at low speed in order to obtain a suspension of organelle D.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
(2 marks)
8
Turn over !
(03)
APW/Jun09/BYA1
Biology Specification A - AQA GCE Mark Scheme 2009 June series
Question 1
(a)
(b)
(c)
(i)
Chloroplast;
(ii)
Photosynthesis;
Uses light (energy);
To produce carbohydrates/starch/glucose/sugars/ATP/reduced NADP;
2 max
Note that candidates cannot be expected to have a detailed knowledge of
photosynthesis
(i)
A;
1
(ii)
C;
1
(i)
Slows enzymes/prevents enzymes being denatured/prevents/
stops self-digestion;
Ignore references to bacteria. Reject enzymes not working
1
(ii)
1
To remove organelle C/ nuclei;
Which are larger/heavier/more dense;
2
Total 8
Question 2
(a)
(i)
C and D;
1
(ii)
Left ventricle with thicker wall/more muscle / (muscle in) left ventricle
contracts more forcefully/beats/pumps more strongly;
1
(b)
Higher in atria/lower in ventricles;
Atrioventricular valves/valves between atria and ventricles open;
2
(Position of valves must be identified. Do not accept an unqualified reference to valves.
Assume pronouns refer to atria.)
(c)
(i)
Atrioventricular node/AVN;
1
(ii)
Bundle of His/Purkyne tissue/;
Accept Purkinje tissue
1
(i)
Allows blood to pass into ventricles/from atria/so that atria can empty;
Before ventricles contract;
2
Ventricle contracts from base / upwards / all blood ejected;
1
(d)
(ii)
Total 9
3
16
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8 The table shows the percentages of different membranes in two animal cells.
Type of membrane
Percentage of total membrane in
Cell R
Cell S
3
5
Rough endoplasmic
reticulum
38
60
Outer membrane of
mitochondria
11
4
Inner membrane of
mitochondria
34
17
3
3
11
11
Plasma membrane
surrounding cell
Lysosome membrane
Other membranes
(a) The main function of one of these cells is to make enzymes. Suggest which cell has
this main function and explain the evidence for your answer.
Cell .....................................................................................................................................
Evidence .............................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(2 marks)
(b)
(i) In both cells the figure for the inner membrane of the mitochondria is different
from the figure for the outer membrane. Explain this difference.
...................................................................................................................................
...................................................................................................................................
(1 mark)
(ii) The appearance of the mitochondria in Cell R is different from the appearance of
the mitochondria in Cell S. Use the figures in the table to suggest how they are
different in appearance.
...................................................................................................................................
...................................................................................................................................
(1 mark)
APW/Jan08/BYA1
17
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(c) Cell R is a eukaryotic cell. Describe two ways in which the distribution of membranes
in cell R is different from the distribution of membranes in a prokaryotic cell.
1. ........................................................................................................................................
.............................................................................................................................................
2. ........................................................................................................................................
.............................................................................................................................................
(2 marks)
Phenylalanine is an amino acid. Scientists investigated the rate of uptake of phenylalanine
by a cell. They changed the concentration of phenylalanine outside the cell and measured
the rate at which it entered the cell. The graph shows the results.
100
80
Rate of entry
into cell / arbitrary
units
60
40
20
0
0
1
2
3
4
5
Concentration of phenylalanine
outside cell / mmol dm–3
(d) The concentration of phenylalanine outside the cell affects the rate at which it enters
the cell. Describe how.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(2 marks)
(e) Phenylalanine enters the cell by facilitated diffusion. Increasing phenylalanine
concentration from 4 mmol dm–3 to 5 mmol dm–3 does not increase the rate at which it
enters the cell. Explain why.
.............................................................................................................................................
.............................................................................................................................................
(1 mark)
Question 8 continues on the next page
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APW/Jan08/BYA1
18
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(f) A centrifuge may be used to obtain a sample of chloroplasts from leaves.
Starting with some lettuce leaves, describe how.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(6 marks)
15
END OF QUESTIONS
APW/Jan08/BYA1
Biology / Biology (Human) - AQA GCE Mark Scheme 2008 January series
Question 8
(a)
(b)
Cell S has more rough endoplasmic reticulum;
Ribosomes are site of protein/enzyme synthesis/
where enzymes are made;
2
(i)
Inner membrane folded/forms cristae;
1
(ii)
Fewer folds/cristae in cell R;
Accept converse; unqualified descriptions refer to cell R.
1
(c)
Only eukaryotic cells have membrane bound organelles;
Nucleus/nuclear envelope;
Endoplasmic reticulum;
Mitochondria;
Lysosomes;
Smaller percentage of membrane is plasma membrane;
Do not have mesosomes;
2
Accept converse; unqualified descriptions relate to cell R. Note that this is an
animal cell. Do not accept general statement about membrane-bound organelles
in addition to rough endoplasmic reticulum/mitochondria and lysosomes.
(d)
Rate of uptake increases then levels out;
At approximately 3 (mmol dm-3 );
2
(e)
Limited by carrier molecules/ proteins/ carriers are saturated;
1
(f)
1 Homogenise/chop (or otherwise crudely break) leaves;
2 Suspend in/mix with buffer;
3 Cold and isotonic;
4 Filter and centrifuge filtrate;
5 At low speed;
6 Discard pellet/keep supernatant;
7 Centrifuge again at faster speed
8 Chloroplasts are in pellet (formed by second centrifugation);
6 max
Total
7
15