Download (a) The structure of a cholera bacterium is different

Q1.
(a) The structure of a cholera bacterium is different from the structure of an epithelial cell
from the small intestine. Describe how the structure of a cholera bacterium is different.
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(5)
(b)
Scientists use optical microscopes and transmission electron microscopes (TEMs) to
investigate cell structure. Explain the advantages and the limitations of using a TEM to
investigate cell structure.
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(5)
(Total 10 marks)
Page 1 of 9
Q2.
(a)
The diagram shows two organelles found in a eukaryotic cell.
A
(i)
B
Name the organelles.
A ..........................................................................................................
B ..........................................................................................................
(1)
(ii)
Explain how the inner membrane is adapted to its function in organelle A.
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(2)
(b)
Give one feature of a prokaryotic cell that is not found in a eukaryotic cell.
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(1)
(c)
Describe how a sample consisting only of chloroplasts could be obtained from
homogenised plant tissue.
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(3)
(Total 7 marks)
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Q3.
The figure shows a section through a palisade cell in a leaf as seen with a light microscope.
The palisade has been magnified × 2000.
x 2000
(a)
Calculate the actual width of the cell, measured from A to B, in μm. Show your working
Answer ........................................... μm
(2)
(b)
Palisade cells are the main site of photosynthesis. Explain one way in which a palisade
cell is adapted for photosynthesis.
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(2)
(Total 4 marks)
Page 3 of 9
Q4.
The diagram shows part of a cell surface membrane.
(a)
Complete the table by writing the letter from the diagram which refers to each part of the
membrane.
Part of membrane
Letter
Channel protein
Contains only the elements
carbon and hydrogen
(2)
(b)
Explain why the structure of a membrane is described as fluid-mosaic.
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(2)
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(c)
When pieces of carrot are placed in water, chloride ions are released from the cell
vacuoles. Identical pieces of carrot were placed in water at different temperatures. The
concentration of chloride ions in the water was measured after a set period of time. The
graph shows the results.
Describe and explain the shape of the curve.
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(3)
(Total 7 marks)
Page 5 of 9
M1.
(a)
2
1
Cholera bacterium is prokaryote;
Does not have a nucleus/nuclear envelope/ has DNA free in
cytoplasm/has loop of DNA;
3 & 4 Any two from
No membrane-bound organelles / no mitochondria / no golgi /
no endoplasmic reticulum / etc;
Maximum of 2 marks for points 3 and 4.
5
Small ribosomes only;
6 & 7 Any two from
Capsule / flagellum / plasmid / cell wall / etc;
Maximum of two marks for points 6 and 7.
5 max
(b)
Advantages:
1
Small objects can be seen;
2
TEM has high resolution;
Accept better
3
Wavelength of electrons shorter;
Advantages: allow maximum of 3 marks.
Limitations:
4
Cannot look at living cells;
5
Must be in a vacuum;
6
Must cut section / thin specimen;
7
Preparation may create artefact
8
Does not produce colour image;
Limitations: allow maximum of 3 marks.
5 max
[10]
M2.
(a)
(i)
A mitochondrion and B nucleus;
(need both for one mark)
1
(ii)
increased surface area;
for respiration/enzymes;
2
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(b)
any suitable feature
e.g. plasmid/capsule/70S ribosomes/smaller
ribosomes/complex cell wall/mesosome/no nucleus;
1
(c)
use of differential centrifugation/or description;
first/low-spin pellet discarded / spin at low speed to remove cell
wall material/cell debris;
supernatant re-spun at higher speed / until pellet with chloroplasts is found;
method of identifying chloroplasts e.g. microscopy;
3 max
[7]
M3.
(a)
16 gains 2 marks;
(accept 15.5 . 16.5)
(principal of calculation i.e.
measured distance (31-33mm/3.1-3.3cm) gains 1 mark)
Mag
2
(b)
relevant adaptation;
and explanation for second mark; e.g.
idea of many chloroplasts / lots of chlorophyll;
to trap or absorb light (energy);
elongated cells;
idea of maximum light absorption / light penetration;
chloroplasts move;
to trap or absorb light (energy);
range of pigments;
can absorb a range of wavelengths / colours / for max light absorption;
large S.A. or cell wall feature e.g. thin / permeable;
for (rapid) CO2 absorption;
2
[4]
M4.
(a) B;
D;
2
(b)
idea of molecules/named molecules moving = Fluid;
idea of both proteins and phospholipids = Mosaic;
2
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(c)
slow rise, sharp rise, levelling off (reject ‘becomes constant’);
diffusion rate increases / description of diffusion rate,
e.g. increase in kinetic energy increases loss of ions;
1
sharp rise / above 50oC proteins are denatured;
levelling off due to concentration of chloride ions in water becoming
equal / maximum loss of Cl- ions;
2 max
[7]
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