OCR AS Biology : Unit 1 (F212) : Cells, exchange and
transport.
Cells B1 Workbook
Measuring Cells
There 3 types of microscope used to study cells: light
microscope, transmission electron microscope (TEM) and Scanning
electron microscope (SEM).
Modern light microscopes can achieve an effective magnification
of up to 1500x and have a maximum resolving power of 200nm.
Electron microscopes can achieve magnifications of up to 500000x
and resolutions of 1nm.
The power of a microscope depends both on its magnification and
resolution.
The higher the resolution of a microscope the greater the detail
you can see.
Units of measurement
1) Complete the diagram below to show: names of the units of
measurement, unit symbols, mathematical operations for converting
between units.
2) Complete the table below to show the corresponding value
nanometres, micrometres and millimetres for the measurements given
in each row. The first row has been completed for you. Ensure that
your answers use the correct unit symbols.
nanometremicrometremillimetre metre
50.0050.0000055 X 10-9
1
1
1
3
7
0.5
2.4 x 10-9
3) When studying cells structure using a microscope the smallest
unit of measurement commonly used to describe findings is the
nanometre. Explain why.
Magnification and Resolution
1) Define the following terms:
Magnification:
Resolution:
2) Visible light has a wavelength of 400-700 nm. Calculate the
best resolution achievable with a light microscope? Show your
working out:
3) If the electron gun produces an electron beam with 2 nm
wavelength, what is the best resolution achievable?
Calculating total Magnification of a compound light
microscope
Eyepiece MagnificationObjective MagnificationOverall
Magnification
X10X4
X10X10
X10X40
X10X100
Calculating Cell Magnification from images
The diagram below shows the general structure of an animal cell
as seen under an electron microscope. Label A H.
_________5m
1) Calculate the magnification factor of the diagram
2) Calculate the length of structure G
3) Calculate the diameter of the nucleolus (structure B)
4) Calculate the diameter of the nucleus
5) Calculate the diameter of the cell at its widest point
The diagram below shows the general structure of a plant cell
when viewed under and electron microscope.
___________ 40m1) Calculate the magnification factor of the
diagram
2) Calculate the thickness of the cellulose cell wall.
3) Calculate the length of the cell.
4) Calculate the length of structure C.
5) Calculate the length of the vacuole.Types of
microscopeFeatureLight MicroscopeTransmission electron microscope
(TEM)Scanning electron microscope (SEM)
Source of image
How is the beam focused
Maximum effectivemagnification
Maximum resolution
Can a live specimen be used?
Section or external view of the specimen
Cost
Can the image be viewed directly
Is staining of the specimen required?
1) Why is the maximum effective magnification of a light
microscope said to be 1500x when it is possible to produce higher
magnifications with improved lenses?
2) Use a named example to explain the need for staining when
using a light microscope.
3) State a possible disadvantage of staining a specimen for
observation when using a light microscope
4) State 2 advantages of using electron microscopes to study
cells over a light microscope.
5) State 2 disadvantages of using electron microscopes to study
cells.
6) Describe with reference to the role of staining how the
transmission electron microscope differs from a scanning electron
microscope?
7) Explain why a vacuum necessary in an electron microscope?
Which microscope?
1) State which type of microscope has been used to create the
image below, give a reason for your answer.
2) The two images below of human chromosomes were produced using
a light microscope and SEM. State which is which; give a reason for
your answer.
3) The image below was produced by staining a section of gut
epithelium. The image is not shown in false colour. Which type of
microscope was used to produce the image? Explain your answer.
4) The three images below are of human cheek cells. One image
has been produced using a light microscope, one using a SEM and one
using a TEM. For each image identify the microscope used and
justify your choice.
Cell structure
Key objectives: Which organelles may be present in a cell and
why? How can we recognise organelles in micrographs / diagrams?
What are the differences between prokaryotic and eukaryotic
cells?
1) Name a type of human cell (not a sperm cell) that is able to
move and explain why this is important to the cells function
2) Why might chloroplasts need to be moved around a plant
cell
3) Many of the cells that line the human respiratory system are
ciliated. Explain why
Which organelles may be present in a cell and what do they
do?
Organelle Diagram StructureFunctionAnimal cell?Plant cell?
Visible under a light microscope
Nucleus
NucleolusThe nucleus is the largest organelle (10-20m
diameter)Roughly spherical.Surrounded by a double membrane called
the nuclear envelopeThe nuclear envelope contains openings called
nuclear pores.Outer membrane joins up to the endoplasmic reticulum
The nucleoplasm contains chromatin (DNA + histones) which can be
seen as dark blobs or fibre.)
Nucleolus is not surrounded by A membraneDense spherical
structure inside the nucleusContains nearly all of a cells genetic
material; instructions for making proteinsControls protein
synthesis (makes mRNA)
Nucleolus makes RNA and Ribsosmes. These pass into the cytoplasm
through the nuclear pores
Yes
Yes
Yes
Ribosome
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Golgi apparatus
Mitochondrion
(mitochondria)
Chloroplast
Lysosome
Centrioles
Plasma membrane
1) Describe three structures / organelles present in generalised
plant cells but absent from animal cells. A) B) C)
2) Name the structures in the diagram below
3) Sperm cells contain large numbers of mitochondria. Explain
why?
4) What evidence can be seen in the diagram that suggests that
the cell is:
metabolically active and involved in secretion of enzymes
[3]
involved in production or modification of lipids? [1]
The diagram is a line drawing of a cell as seen with an electron
microscope. 20 mACDBEFGH
Complete the table by matching the label to the function and
then naming the appropriate part. The first one has been completed
for you.
Function of StructureLabelName of Part of the Cell
Controls the activity of the cell.ANucleus
Protein/polypeptides are made here.
Aerobic respiration takes place here.
Produces secretary vesicles.
Controls the entry of substances into the cell.
Contains hydrolytic enzymes.
Makes lipids, including steroids.
By reference to the diagram: Is the cell that of an animal or a
plant? Give a reason for your answer.
Identifying organelles from micrographs
1) Name the large round organelle in the micrograph below 2) Is
it found in animal or plant cells3) Name the structures A,B and
C
4) Name the large organelle shown in the micrograph below5) Is
it found in animal or plant cells?6) Suggest what structure D could
be
7) Name the organelle shown in the micrograph below8) State the
role of the organelle
9) Name the structures visible in the transmission electron
micrographs below
10) Name the structure shown in the micrograph below
11) Name the structure shown in the micrograph below
Test yourself on a full cell micrograph
Is this an animal or plant cell? Can you name the structures
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Parts of the cell working together
Complete the paragraph below to describe how organelles in a
cell work together to produce and secrete proteins such as
hormones
The nucleus carries all the necessary instructions for the cell
to function. The code for protein synthesis is carried in the
____________ which are made of ____________ or histones. The
instructions are ____________ or copied into mRNA (messenger
ribonucleic acid). The mRNA then leaves the nucleus via the
_________________ and travels to the ______________ where the
message is read and translated into protein. The newly manufactured
proteins are transported to forming face of Golgi body/apparatus in
transport __________. Within the Golgi apparatus the proteins are
processed. Vesicles are budded off from the maturing face of Golgi
and are transferred to the ___________________ for secretion.
Glandular cells (e.g. pancreas) contain large amounts of
__________________ (this is encrusted with ribosomes and is where
protein synthesis takes place) and Golgi body. These cells also
contain many mitochondria since protein synthesis requires a lot of
__________.
(ii) State the function of structures B. [1]
(iii) Describe the role of structure C in secretion. [3]
Prokaryotes and Eukaryotes
1) The diagram below shows Staphylococcus, which is a
prokaryotic cell. Label parts A to D
2) The following table compares some features of a prokaryotic
and eukaryotic animal cell. Complete the table by using present,
absent or a short descriptive phrase. The first has been completed
for you.
Cellular FeatureProkaryotic CellEukaryotic Animal Cell
Cell wallPresentAbsent
Cell surface membrane
Nucleus
Membrane bound organelles
DNA
Plasmids in the cytoplasm
1) Fill in the gaps
It was once common practice to classify all living organisms as
either animals or plants. With improved knowledge of living things
it has become apparent that there are ______ fundamentally
different types of cell. The most obvious difference between the
two types is that one possesses a nucleus and the other does
not.
The cells of animals, ___________ and fungi contain many
organelles some of which are bound by a membrane. These are
referred to as ______________ cells. The cells of bacteria are very
different, they lack membrane bound organelles such as a
_____________. This type of cell is referred to as a
_______________ cell (meaning before nucleus). Prokaryotic cells
are about 1000 to 10000 times smaller than eukaryotic cells and are
much simpler in structure. Biologists believe eukaryotes evolved
from ________________.
2) Eukaryotic cells contain membrane bound organelles, give 5
examples:
3) Prokaryotic cells have one membrane, where is it?
4) Use table 1 to compare plant (eukaryote), animal (eukaryote)
and prokaryotic cells. For each cell type indicate whether the
feature is present or absent using a tick or cross.
FeaturePlant cellsAnimal cellsProkaryote cells
Chloroplasts
Large permanent vacuole
Cellulose cell wall
Peptidoglycan (murein) cell wall
Linear chromosome
Circular chromosome
Plasmids
Endoplastic Reticulum
Golgi body
DNA free in the cytoplasm
ATP is produced in the mitochondria
ATP is produced at infolded regions of the cell membrane called
mesosomes
Undulipodia contain 9 + 2 circular arrangement of
microtubules
Flagella made form spiral protein called Flagellin
Ribosomes
Cell membrane
5) Give 2 ways in which prokaryotes are useful to humans
6) Mitochondria and chloroplasts contain small loops of DNA
similar to the plasmids found in prokaryotic cells. These
organelles also contain ribosomes that are the same size as
prokaryotic ribosomes. Can you suggest an explanation for these
features?
7) Give one way in which a eukaryotic plant cell is similar to a
prokaryote.
8) Give two ways in which a eukaryotic plant cell is different
from a prokaryote.
9) Label the highlighted features on the diagram of the
bacterium E.coli shown in the diagram below.
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