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  • Created on: 06-01-13 14:00
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fboco 1
Cell structure
a) State the resolution and magnification that can be achieved by a light microscope, a
transmission electron microscope and scanning electron microscope.
Magnification Resolution
Light microscope 2 000 x 200 nm
Scanning electron 500 000 x 0.5 nm
Transmission electron 100 000 x 3- 10 nm
b) Explain the difference between magnification and resolution
Magnification - Is the degree to which the size of an image is larger than the object itself.
Resolution ­ Is the degree to which it is possible to distinguish between two objects that
are very close together
c) Explain the need for staining samples for in light microscopy ad electron microscopy.
Coloured stains are chemicals that bind to chemicals on or in the specimen.
This allows specimen to be seen. Some stain bind to specific cell structures.
Acetic orcein stains DNA dark red. Gentian violet stains bacterial cell walls.
d) Calculate the linear magnification of an image
A = Actual image size
I = Image size
M = Magnification size
e) Describe and interpret drawings and photograph 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 and cilia
f) Outline the functions of organelles listed in e)

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- Nucleus - Controls cellular activity
- Nucleolus - Makes the RNA and ribosomes
- Nuclear - Has nuclear pores that allows large molecules to
envelope pass through
- Rough and - Transport proteins made in the ribosomes
smooth attached to the rough ER
reticulum (ER)
- Golgi - Modifies and packages proteins
- Ribosomes - Makes proteins
- Mitochondria - Make ATP (adenosine triphosphate)
- Lysosomes - Makes enzymes that breaks down wastes and
worn out organelles
- Chloroplasts - Site…read more

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i) Compare and contrast with the aid of diagrams and electron micrographs the structure of
prokaryotic cells and eukaryotic cells
Prokaryotes Eukaryotes
No membrane bound Have membrane bound
organelles organelles
Slippery layer called
DNA not in membrane but Have a true nucleus
in nucleoid
ATP produced in ATP produced in
mesosomes mitochondria
j) Compare and contrast with the aid of diagrams and electron micrographs, the structure of
plant cells and animal cells
Plant cells have a cell wall.…read more

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Cell membranes
a) outline the roles of membranes within cells and at the surface of cells
They control the entrance/exit of molecules into the cell through the means of active and
passive transport. They also maintain a difference in charge between the inside/outside of
the cell. In addition, they have large surface area that allows reactions to take place at a
fast rate (e.g. mitochondria).…read more

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f) explain the term cell signalling
It is the response of cell to their environment based on molecules that may affect the cell's
functions. It is also the communication of cell amongst one another through the means of
chemical molecules such as hormones.…read more

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Cell Division, Cell Diversity and Cellular organisation
a) State that mitosis occupies only a small percentage of the cell cycle and that the remaining
percentage includes the copying and checking of genetic information;
Mitosis is only a small percentage of the cell cycle. The remaining
percentage of the cycle is composed of the s phase (genetic
duplication), growth phase 1 and growth phase 2.…read more

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d) explain the significance of mitosis for growth, repair and asexual reproduction in plants and
Mitosis allows growth and repair of the organism's body as it produces identical cells.
Mitosis makes the daughter cells genetically identical therefore ensuing that the daughter
cells can perform the same functions as that of its parent cell. It is also essential for asexual
reproduction. In asexual reproduction the offspring produced is a genetically identical to
the parent organism, a clone.…read more

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Neutrophils has many lysosomes to kill
retained their nucleus ER and Golgi
apparatus to produce enzyme and
Epithelial cells have cilia that propel mucus
has a large surface area
Have many mitochondria to produce
ATP for cilia propulsion.…read more

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a)explain, in terms of surface area: volume ratio, why multicellular organisms need specialised
exchange surfaces and single-celled organisms do not (HSW1);
Multicellular organisms have a smaller surface area to volume ratio compared to single celled
organisms. This means that the surface area of the organism is not enough to sustain en efficient
exchange of gases and nutrients. The size of the organism also affects the need for a specialised
exchange surface.…read more

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During expiration:
The pressure
The diaphragm inside the lungs The change in
The volume of the
is higher than the pressure drive s
and intercostal chest cavity
the air out of the
muscles relax decreases pressure outside
g)explain the meanings of the terms tidal volume and vital capacity;
Vital capacity The maximum volume of air that can be expelled after the maximum
Tidal volume The lung volume that is expelled during normal inhalation and exhalation.…read more




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