F211 Biology 'AS' Level 2011
Name ………………………………………………..
Content You should be able to:
a) state the resolution and magnification that can be achieved by a light
microscope, a transmission electron microscope and a scanning electron
microscope;
b) explain the difference between magnification and resolution;
c) explain the need for staining samples for use in light microscopy and electron
microscopy;
d) calculate the linear magnification of an image (HSW3);
e) describe and interpret drawings and photographs of eukaryotic cells as seen
under an electron microscope and be able to recognise the following structures:
nucleus, nucleolus, nuclear envelope, rough and smooth
endoplasmic reticulum (ER), Golgi apparatus, ribosomes,
mitochondria, lysosomes, chloroplasts, plasma (cell surface)
membrane, centrioles, flagella & cilia;
f) outline the functions of the structures listed in (e);
g) outline the interrelationship between the organelles involved in the production
and secretion of proteins (no detail of protein synthesis is required);
h) explain the importance of the cytoskeleton in providing mechanical strength to
cells, aiding transport within cells and enabling cell movement;
i) compare and contrast, with the aid of diagrams and electron micrographs, the
structure of prokaryotic cells and eukaryotic cells;
j) compare and contrast, with the aid of diagrams and electron micrographs, the
structure and ultrastructure of plant cells and animal cells
Resources
Video:
Subcellular fractionation
The Electron microscope
The Living Plant Cell
The Plasma Membrane
Introduction to Living Cells
DVD:
Keeping it all together
Computer: Images of Biology
Virtual Biology Lab.
The Cell – structure, function & processes
Introduction to Cells – The Drama of Reproduction
VLE:
Fibroblasts
Science / Biology / Year12 / AS Biology / Module 1 Cells / 1 Cell Structure
Cell structure
Cell size
Cells and organelles
Interactive cell organelle activity

Revised
Notes
Unit 1 Module 1 Topic 1
References
Topic 1.1.1
Textbooks
Consult your issued textbooks in the first instance, then look at other textbooks in the library for
alternative diagrams, other examples or further explanations. For more specialised books, ask for
advice or use the keyword system in the library.
Articles
Biological Sciences Review:
Vol.3 No.3
Vol.4 No.1
The Cell Nucleus
A Cloistered Existence: life in a
plant cell wall
Vol.4 No.2 The Golgi Apparatus: the
distribution centre of the cell
Vol.4 No.3 Mitochondria: power stations of
the cell
Vol.6 No.3 Cilia
Vol.8 No.4 No visible means of support
(Cytoskeleton)
Vol.13 No.1 High tension – cell specialization
& transport in plants
Vol.17 No.2 Lysosomes The cell's recycling
centres
Vol.17 No.3 Lysosomes and their versatile
but potentially fatal membranes
Vol.18 No.4 The beat goes on: cilia &
flagella
Vol.19 No.3 Light microscopy
Vol.19 No.4 Electron microscopy
Vol.20 No.1 Scanning electron microscopy
Vol.20 No.1 Cell suicide
Vol.21 No.2 A twist in the tail
Vol.21 No.2 CELLpics
Vol.21 No.4 Chloroplasts: biosynthetic
powerhouses
Fact of Life
Websites
www.microscopy-uk.org.uk/
www.pbrc.hawaii.edu/bemf/microangelo
www.cellsalive.com
http://cellpics.cimr.cam.ac.uk/
Keywords
Cell
Cell wall
Cellulose
Centriole
Chloroplast
Chromatin
Cilium
Crista
Cytoskeleton
Electron Microscope (EM)
Endoplasmic reticulum (ER)
Eukaryote
Flagellum
Golgi apparatus
Histone
Light Microscope
Lysosome
Matrix
Microfilament
Microtubule
Middle lamella
Mitochondrion
Nuclear envelope
Nucleolus
Nucleus
Organelles
Most animal cells are extremely small, ranging in
diameter from about 10 to 150 µm. However a
nerve cell can be over a metre long and the egg cells
of birds may be several centimeters in diameter.
The largest egg cell is that of the ostrich which may
be more than 10cm in diameter, and have a volume
equal to that of two dozen hen's eggs.
Plasma membrane
Prokaryote
Resolution
Ribosome
Scanning EM
Spindle
Tonoplast
Transmission EM
Ultrastructure
Vacuole
Vesicle
NB Errors in Biology 1:
Page 14, Column 2, line 6: endocytosis should read exocytosis.
Page 15, Column 1, lines 9 & 10: the words grana and thylakoids
have been interchanged.
Page 261: grana incorrectly defined.
The Light Microscope
Specimens are often colourless so stains are used to make structures easier to see
Stain
Methylene Blue
Acetic orcein
Eosin
Haemotoxylin
Iodine solution
Light green
Acidified phloroglucinol
Use
Colours produced
Practical: Examining Animal Cells
Risk Assessment
List all the possible hazards and risks associated with this practical and identify the precautions that
you will need to take.
Method
 Take a cotton bud from a newly opened pack. Move it over the inside of your cheek on one side of
your mouth.
 Smear the cotton bud over a small area in the centre of a clean microscope slide.
 Immediately place the cotton bud into a container of 1% sodium hypochlorite solution.
 Allow the smear to air dry.
 Heat-fix the smear by passing the slide quickly through the blue flame of a Bunsen burner.
 Place two drops of 1% methylene blue stain onto the smear and leave for one minute.
 Rinse off the methylene blue.
 Dry the slide and add a drop of distilled water to the stained smear.
 Cover with a coverslip and observe the cheek cells under the microscope. Use low power first.
 Draw three cheek cells as seen under high power. Label cytoplasm, cell membrane and, nucleus.
 Measure the diameter of a cheek cell and the diameter of a nucleus, add to your diagram..
 When the cells have been observed place your slides, with their coverslips, into a pot of Virkon.
Practical: Examination of plant cells
Introduction
If you cut an onion bulb in half and then separate the fleshy leaf bases you will be able to peel off the thin,
one-cell thick epidermis layer that is between them. As the epidermis is one-cell thick, provided that it is
laid flat on a microscope slide, the transparent cells will be seen. Iodine/KI solution will stain the cells and
enable you to more clearly see the nucleus, nucleoli, cytoplasm and cell wall. You may be able to
distinguish the large vacuole inside the cell. You may also be able to see the middle lamella between
adjacent cells.
The shape of each cell in the epidermis layer is partly determined by the pressure of other cells around it.
If a single cell were isolated it would be rounded or oval. In some cells the nucleus will appear near to one
edge of the cell and is some the nucleus will appear in the centre of the cell, but it is still surrounded by
cytoplasm connected by strands to the cytoplasm lining the wall.
Risk Assessment
List all the possible hazards and risks associated with this practical and identify the precautions that you
will need to take.
Method
 Place 2 drops of iodine/KI solution onto a clean microscope slide.
 Peel off a small piece of onion epidermis from between two fleshy leaf bases of an onion bulb and
place it, flat on the slide, in the iodine solution.
 Carefully add a coverslip and blot off any surplus liquid.
 Observe the slide. Use the lowest power objective first and then use the 10 and 40 objectives.
 Draw two or three cells. Label as many structures as you can see.
 Measure: the length of a cell, the width of a cell, and the diameter of a nucleus.
1 In the table below
the scale of
Magnification is a logarithmic scale, each unit on the scale is 10 times as large as the preceding one. Thus the
divisions become progressively compressed towards the upper end. Place the following objects in the correct
boxes on the scale. For some of these you will need to make an inspired guess!
adult human
bacteria
haemoglobin molecule
human sperm
virus
mitochondrion
chloroplast
large virus (HIV)
onion epidermis cell
haemoglobin molecule
human liver cell
ribosome
cilium
hen egg
Division
Objects
10–100m
Large building
Giant squid
Tall tree
1–10m
100mm–1m
10–100mm
1–10mm
100m–1mm
10–100m
1–10m
100nm–1m
10–100nm
1–10nm
0.1–1nm
Below 0.1nm
Red blood cells
human egg
Amoeba
giant squid
atom
Read P 2-5 Complete the following table to define the following terms:
Term
Magnification
Definition
The object looks …………..!
Magnification = ………………………………..
Resolution
Is the degree to which it is possible to ………………………………....
………………………………………………………………………….
It is determined by …………………………………………………….
The ….……… wavelengths give the ……….. resolution eg blue light
1µm is 1/1000 of a mm
1nm is 1/1000 of a µm and so
The resolution of the human eye is 100µm
This means that we can’t see objects that are smaller than 0.1mm (1/10 of a mm)
The resolution of the light microscope is 200nm
This means that the smallest thing we can see on a slide is 0.0002mm (1/2000 of a mm)
The resolution of the electron microscope is 0.20nm
This means we can see things as small as 0.0000002mm (1/2000000 of a mm)
The diagram below shows a mitochondrion, as seen using an electron microscope.
Calculate the actual length of this mitochondrion and show your working.
Now study the worked examples in your text book and complete SAQ 1,2,3 and 4.
The Electron Microscope
The light microscope is relatively cheap and easy
to use. Whole and living specimens can be used
and, using dark ground illumination, transparent
objects can be viewed without staining. However,
above magnification of 1500 the image may
become blurred. This is due to limits on the
resolution of the light microscope. Visible light has
a range of wavelengths of 400–700nm. Some of
the organelles inside cells are smaller than this so
the light cannot get in between these objects.
Hence, two small objects closer together than
700nm, will be seen as one blurred object.
Electron microscopes are very expensive and
require a high degree of skill and training to
operate. Preparation of materials is lengthy and
often involves the use of highly toxic stains.
Specimens have to be viewed in a vacuum so living
material cannot be observed. Images are always in
black, white or grey, although false colour can be added using computers.
Instead of a beam of light, a beam of electrons is used. In light microscopes the beam of light
is focussed onto the specimen by a condenser, which is a thick glass lens mounted under the
stage. In electron microscopes the condenser is a vertical magnetic field produced by the
cylindrical electromagnet that straightens and intensifies the electron beam. The radiation
passes through the specimen and is focussed by an objective lens. The final image is focussed,
by a projector lens, onto a viewing screen coated with a fluorescent compound, such as zinc
sulphide. When irradiated with electrons the fluorescent substance emits light visible to the
human eye. The final image is photographed to produce an electron micrograph. (Photographs
taken of specimens seen under the light microscope are called photomicrographs.)
The wavelength of electrons is 0.05 nm. This should produce a corresponding increase in
resolution but there are technical difficulties that prevent this increase being realised. The
resolving power is actually about 0.20 nm. Clear images of at least 200 000 – 300 000
magnification can be obtained using the electron microscope,
Golgi apparatus
Scanning Electron Microscope (SEM) image of a flea
Light Microscope
Transmission Electron Microscope
Use the diagrams above, your textbook and the previous notes page to compare the Electron
Microscope and Light Microscopes then fill in the table below:
TEM
LM
Power Source
Lenses made of
Preparation of
specimens
State of Specimen
Resolution
Magnification
Advantages
Disadvantages
SEM
Resolution is
Magnification is
Drawing of an Electron-micrograph of an Animal cell
Drawing of an Electron-micrograph of a Plant cell
Organelle
Nucleus
Nucleolus
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Golgi Apparatus
Mitochondria
Chloroplast
Lysosomes
Ribosomes
Centrioles
Structure
Function
Complete the table below to compare the structure of animal and plant cells (use present/absent)
Structure
Cell wall
Cell membrane
Cytoplasm
Large vacuole
Mitochondria
Chloroplast
Endoplasmic reticulum
Ribosomes
Tonoplast
Cilia
Flagella
Cytoskeleton
Golgi apparatus
Lysosomes
Centrioles
Plant cell
Animal cell
How the organelles work together to produce and secrete a protein such as INSULIN
study the diagram, use your textbook and fill in the table below to explain what is happening at each point.
Step
What is happening in the diagram
1
2
3
4
5
6
7
8
9
The Cytoskeleton
Role
Provides
Mechanical
Strength to cells
Aids
Transport within
cells
Enables
Cell
Movement
http://www.biology.arizona.edu/cell_bio/tutorials/cytoskeleton/main.html
How this role os achieved
A Bacterium is a PROKARYOTIC cell(Pro=before, karyotic= nucleus, so the term
means, the cell has No Nucleus!)
But there are other differences to eukaryotic cells, cells that do have NUCLEI
Structure
Eukaryotic cell
Prokaryotic cell
Size
Cell wall
Nucleus
Genetic material
mitochondria
chloroplasts
ribosomes
Endoplasmic reticulum
cytoskeleton
Cilia and flagella
Slime capsule
Review Questions
Staphylococcus, which is a prokaryotic cell.
Label parts A to D
Staphylococcus
This diagram shows the general structure of an animal cell as seen with an electron microscope.
Match the letters on the diagram with their structures and with each structure’s correct function.
Choose structures from the list below:
smooth endoplasmic reticulum
nucleolus
nucleus
microvilli
microtubule
cell membrane
nuclear envelope with pores
ribosome
Golgi apparatus
centriole
rough endoplasmic reticulum
lysosome
mitochondrion
vesicle
chromatin
Functions
1
Controls movement of substances into and out of the cell. Contains marker molecules, usually
glycoproteins or glycolipids, so that the body’s immune system can recognise them as self (or nonself in the case of transplanted cells). Has receptor sites for hormones and neurotransmitters.
Where the aerobic stages of respiration occur. The link reaction and Krebs cycle occur in the
matrix and oxidative phosphorylation occurs on the cristae.
These consist of two sub-units, one large and one small. In eukaryote cells they are 80s type. They
are the sites of protein synthesis.
Here proteins are modified, by addition of carbohydrates, to form glycoproteins. Lipids are
modified and stored and lysosomes are formed. Secretory enzymes are produced here.
Releases enzymes to the outside of the cell by exocytosis
Increases the surface area for absorption
Made of DNA and protein and found in the nucleoplasm. Will form chromosomes when the cell is
dividing.
Makes ribosomal RNA and ribosomes. It is a highly organised sub compartment of the nucleus that
disappears during mitosis and reforms after nuclear division.
Retains the chromatin and controls the cell’s activities.
Letter on diagram
Name of structure
A
B
C
D
E
F
G
H
I
The diagram below shows an animal cell
Function of structure (as indicated by
number of textbox)
_________
5m
Diagram showing the general structure Of an animal cell as seen under the electron microscope
Fill in the missing labels
Calculate the magnification factor
Calculate the length of structure G
Calculate the diameter of the nucleolus
Calculate the diameter of the nucleus
Calculate the diameter of the cell at its widest point
The diagram below shows a plant cell
___________
40m
Diagram showing the generalised structure of a plant cell as seen with an electron microscope
Label the structures A – L.
Calculate the magnification factor.
Calculate the thickness of the cellulose cell wall.
Calculate the length of the cell.
Calculate the length of structure C.
Calculate the length of the vacuole.
This is a diagram showing the general structure of a plant cell.
nucleus
nucleolus
chloroplast
mitochondrion
polysomes
tonoplast membrane
cell wall
plasma membrane
microtubules
vacuole
rough endoplasmic reticulum
Golgi apparatus
Match the letters on the diagram with their structures and with each structure’s correct function
Structures – choose from the following
Functions
2
Bound by a double membrane or envelope. The inner layer is folded into lamellae. Thylakoid
membranes contain chlorophyll and are the site of the light dependent reaction of photosynthesis.
The gelatinous matrix, the stroma, is where the light independent stage of photosynthesis
takes place.
Made of cellulose, a polymer of -glucose. It gives strength and shape to the cell and is totally
permeable.
Contains cell sap – a solution of mineral salts, sugars, oxygen, carbon dioxide, enzymes, pigments
and waste products. It helps regulate osmotic properties of the cell.
Site of aerobic respiration – link reaction, Krebs cycle and oxidative phosphorylation.
Surrounds the vacuole and regulates entry/exit of substances into/out of the vacuole
Regulates entry and exit of substances into and out of the cell
It is here that proteins manufactured in the cell are modified.
Its surface is covered with ribosomes. Here, newly manufactured proteins pass along the cisternae
towards the Golgi apparatus.
Contains the chromatin. Controls the activities of the cell.
Letter on diagram
A
B
C
D
E
F
G
H
I
Name of structure
Function of structure (as indicated by
number of textbox)
Complete the table below to indicate whether the feature is always (A), almost always (AA), sometimes (S) or
never (N) present.
Feature
Chloroplasts
Large permanent vacuole
Cellulose cell wall
Centrioles
Centrosome (region containing the
two centrioles)
Histone proteins (associated with
DNA on chromosomes)
Nucleus
Golgi body
Plasmids
Flagellum with 9 microtubule triplet
arrangement
Plasmodesmata
Cilia
Pili
Linear chromosomes
Mitochondria
Glycogen
Ribosomes
Mesosome
Cell membrane
Cholesterol in membranes
Flagella with flagellin protein
Starch
Can undergo mitosis
Plant cells
Animal cells
Prokaryote cells
Decide whether the following statements are true or false and circle the appropriate letter.
At the base of each cilium is a centriole.
T
F
Ribosomes can be free in cytoplasm.
T
F
Viruses have no cytoplasm.
T
F
Bacteria store glycogen.
T
F
Bacterial cell walls are made of cellulose.
T
F
Both chloroplasts and mitochondria have inner and outer membranes.
T
F
Bacteria cannot carry out mitosis.
T
F
Bacterial plasmids are used as vectors in genetic engineering.
T
F
Bacterial flagella contain a 9 + 2 arrangement of microtubules.
T
F
Lipids are synthesised in rough endoplasmic reticulum.
T
F
Viruses have no cell membrane.
T
F
Prokaryotes have 80s ribosomes.
T
F
Fungi, algae and protoctists are all eukaryotes.
T
F
Prokaryotes have naked DNA, with no histone proteins.
T
F
Viruses do not have a cellular structure.
T
F
Mitochondria and chloroplasts both contain DNA.
T
F
Resolution is greater at higher wavelengths
T
F
Eosin is used to stain dead cells
T
F
All cells have a cytoskeleton
T
F
Plant cells contain centrioles
T
F
Specimens that have been viewed under the EM divide rapidly
T
F
REVISION Chapter 1 Cell Structure P.1 - 21
Referring to your textbook, you should be able to describe/explain why each of the
topics below or tissues named are important in Cell Structure. Use SAQ to help and
try the past question at the end of the chapter



Microscopes
o Light microscopes
 Condenser lens
 Objective lens
 Staining and types of stain
o Magnification
(SAQ 1,2,3,4)
o Resolution
o Electron microscopes
 TEM
 SEM
(SAQ 5)
Cells
o Appearance under light microscope
o Appearance under electron microscope
(SAQ 6,7)
Structure and function of Organelles
o Nucleus
 Nuclear envelope
 Nuclear pores
 Chromosomes
 Chromatin
 Nucleolus
 Ribosomes
o Endoplasmic reticulum
 Cisternae
 RER
 SER
o Golgi Apparatus
 Vesicles
 Endocytosis
 Secretion
o Lysosomes
 Acrosome
o Chloroplasts
 Grana
 Thylakoids
 Stroma
 Starch grains
o Mitochondria
 Cristae
 Matrix
 Aerobic respiration
 ATP
 Faulty mitochondria
o Vacuole
o Plasma membrane
o Centrioles
 Microtubules
Preparing for the Test
The test will consist of past AS questions and will
be marked according to the AS mark scheme.
Make sure that you have




Read the contents list on your TOPIC
SHEET
Read all your class notes, are they up to
date? (copy up if you missed a lesson
including microscope work)
Read through the Pate’s booklet
including diagrams and try all the past
questions in it. USE the VLE!!
Made your own summary notes/mind
maps/keyword lists, if you do this
carefully as we go through each chapter,
you’ll have them all ready for the
summer revision period!
Any Problems?
Indicate on your notes any areas that you are
having difficulty with eg highlighting in
pink/green/underline in pencil!
What is the reason:
Is it lack of understanding?
Were you away when we did the work?
Ask before the test if you need help!
If you prepare thoroughly, you’ll be fine!!
Don’t Panic!!
o Cilia and Flagella
o The cytoskeleton
o Cell walls (SAQ 8)
 Prokaryotic cells
o Structure of prokaryotic cell
o Comparison to eukaryotic cells
Past Questions 1,2,3,4,5 P. 22-23
CS
26/5/11

Tubulin and spindle
A Past Question!
1 Fig. 1.1 is a diagram of an animal cell as seen using a transmission electron microscope.
(a) (i) Name the structures of the cell labelled A, B, C and D.
A ………………………………………………
B ………………………………………………
C ………………………………………………
D ……………………………………………… [4]
(ii) Structures C and E are examples of the same organelle.
Suggest why E looks so different to C.
......................................................................................................................................................................
......................................................................................................................................................................
......................................................................................................................................................................
................................................................................................................................................................ [2]
(iii) Calculate the actual length of structure C.
Show your working and give your answer in micrometres (μm).
Answer = .................................................. μm [2]
(b) Proteins are produced by the structure labelled F. Some of these proteins may be extracellular
proteins that are released from the cell.
Outline the sequence of events following the production of extracellular proteins that leads to
their release from the cell.
..................................................................................................................................................
..................................................................................................................................................
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..................................................................................................................................................
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............................................................................................................................................ [3]
[Total: 11]