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Biology Specification Led Revision
Foundations in Biology:
2
...
1 Cell Structure
(a) The use of microscopy to observe and investigate different types of cell and cell structure in a
range of eukaryotic organisms
...
)
Light Microscope
• Pass light through the sample material
• Much lower resolution and magnification than that of electron microscopes
• Maximum resolution of about 0
...

Laser Scanning Confocal Microscopes
• Use laser beams to scan a specimen tagged with florescent dyes
• A splitter, splits a beam of light over the specimen and when the laser hits the dyes it emits
fluorescent light
• Florescent light is focused into a pinhole onto a detector which then generates an image
• Used to look at objects at different depth in thick specimens
• Multiple images can be taken to generate a 3D image
Instrument
Light Microscope

Maximum Magnification

Maximum Resolution

x1 500

200nm

Transmission electron
microscope

x500 000

0
...
(Including the
use of an eyepiece graticule and stage micrometer
...
1 mm long
3) At this magnification, 1 division on the stage micrometer is equivalent to 4
...
1 / 4
...
02mm
6) If an object under the microscope is 20 epu in length then 20 x 0
...
4 mm long

(c) the use of staining in light microscopy (To include the use of differential staining to identify
different cellular components and cell types
...

• Start by pipetting one drop of water onto a life and use tweezers to place th specimen on top of
the water drop
• Put a cover slip on top by standing it upright and the lowering it down over the water
• Try not to get air bubbles

Now you can add a stain
• Place a drop of the stain at one side of the slip
• then put a paper towel on the other side and the stain will draw itself through
(d) the representation of cell structure as seen under the light microscope using drawings and
annotated diagrams of whole cells or cells in sections of tissue
...
05mm wide the magnification
is:
Image = 5mm
Object = 0
...
05mm = 100 = x100 magnification
Calculating Image size:
If your specimen is 0
...
1 mm
Magnification = x20
Image = 0
...
1 mm Object size
Converting Units:
All units must be the same when applying them to the formula
Unit

How many millimetres it is:

(x 1000) Millimetre (mm)

1 mm ( / 1000)

(x 1000) Micrometer

0
...
000 001 mm ( / 1000)

(f) the difference between magnification and resolution (To include an appreciation of the
differences in resolution and magnification that can be achieved by a light microscope, a
transmission electron microscope and a scanning electron microscope
...

Instrument
Light Microscope

Maximum Magnification

Maximum Resolution

x1 500

200nm

Transmission electron
microscope

x500 000

0
...

• Electrons have a much shorter wavelength than light, so a higher resolution is possible with an
electron microscope
(g) the ultrastructure of eukaryotic cells and the functions of the different cellular components (To
include the following cellular components and an outline of their functions: nucleus, nucleolus,
nuclear envelope, rough and smooth endoplasmic reticulum (ER), Golgi apparatus, ribosomes,
mitochondria, lysosomes, chloroplasts, plasma membrane, centrioles, cell wall, flagella and cilia
...

• The nucleus contains chromatin (which is made from DNA and proteins) and often a structure
called the nucleolus
...
e
...

• Vesicles seen at the edges of the sacs
Function
• To process and package new lipids and proteins
• Makes lysosomes

Mitochondrion
Description
• Usually oval shaped
• Has a double membrane
• Inner = Forms cristae (folded structures)
• Outer = Outer membrane around the organelle
• The matrix is formed inside of the space inside the organelle, where enzymes which are involved
in respiration are kept separate from the cytoplasm
Function
• Site of aerobic respiration, where adenosine triphosphate is formed
• Mitochondria are found in large numbers in active cells (i
...
muscles)

Chloroplast
Description
• A small, flattened structure found in plant cells
• Surrounded by a double membrane
• Inner membranes = Thylakoid membranes
• Thylakoids stacked together to form Grana
• Grana are held together by lamellae
Function
• Site where photosynthesis takes place

Centriole
Description
• Small, hollow cylinders, made of microtubules
• Found in animal cells, but only on some plant cells
Function
• Involved in the separation of chromosomes during cell division

Cilla
Description
• Small, hair like structures found on the surface of the membrane of some animal cells
• In cross section they have an outer membrane and a ring of 9 microtubule pairs and a single pair
in the centre
Function
• Microtubules allow the cilia to move
• This movement is used by the cell to move substances along the cell surface

Flagellum
Description
• Flagella on eukaryotic cells are like cilia but longer
• They stick out from the cell surface and are surrounded by the plasma membrane
• Inside are like cilia too, with 9 pairs of microtubules and one lone pair in the middle
Function
• The microtubules contract to make the flagella move
• Flagella are used by cells like an outboard motor to move the cell forward

(h) photomicrographs of cellular components in a range of eukaryotic cells (To include
interpretation of transmission and scanning electron microscope images
...
Proteins are produced on the ribosomes on the RER and are folded and processed in the
Rough Endoplasmic Reticulum
...
They're then transported through the cytoskeleton in vesicles to the Golgi apparatus
3
...
The proteins enter more vesicles to be transported around the cell

(j) the importance of the cytoskeleton (To include providing mechanical strength to cells, aiding
transport within cells and enabling cell movement
...

Feature

Prokaryotic Cells

Eukaroyic Cell

Size

Extremely small cells ( less then 2 Larger Cells (about 10-100
micrometer diameter)
micrometers diameter)

DNA

Circular DNA

Linear DNA

Nucleus

No nucleus - DNA is free in
cytoplasm

Nucleus present - DNA is inside of
it

Cell Wall

Cell wall made of polysaccharide
but not cellulose or chitin

No cell wall (animals)
Made of Cellulose (Plants)
Made of chitin (Fungi)

Membrane Bound organelle

Few organelle and no membrane
bound

Many organelle, lots membrane
bound organelle

Flagella

When present made of the protein Flagella made of microtubules in
flagellin, arranged in a helix
9+2 structure

Ribosomes

Small Ribosomes (70s)

Larger ribosomes (80s)

Example

E

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