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Microscopes
Magnification- the number of times bigger an image is than the
object.
Resolution- the ability to distinguish to close together points as
distinct from each other
Light Microscope Transmission Scanning
Electron Electron
Microscope Microscope
Magnification X1,500 X500,000 X100,000
Resolution 200nm 0.1nm 0.1nm
Advantages Inexpensive Good Good
magnification magnification
and resolution and resolution,
3D images
produced
Disadvantage Low magnification Samples have to
s and resolution be dead,
samples have to
be in a vacuum,
extremely
expensive and
require high
degrees of skill
and training.…read more

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Actual Size (m)
To convert from mm to m times by 1000.
Organelles
Nucleus- Contains the genetic information of the cell
Nucleolus- Makes RNA and ribosomes
Nuclear envelope- Contains holes called nuclear pores,
which allow relatively large molecules to pass through
Rough endoplasmic reticulum- Transport proteins that
were made on the attached ribosomes.
Smooth endoplasmic reticulum- Makes lipids and
steroids.
Golgi apparatus- Modifies proteins and packages them
into vesicles. They can then be transported to the surface for
exocytosis.…read more

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Production and Secretion of Proteins
1. The instructions to make proteins are in the nucleus of the
cell
2. The gene containing the instructions for the production of
the hormones is copied onto a piece of mRNA
3. The mRNA leaves the nucleus through the nuclear pores
and attaches to a ribosome.
4. The ribosome uses the codes to assembled the protein
5. The assembled proteins inside the rough ER is `pinched off`
in a vesicle and transported to the Golgi apparatus.…read more

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Golgi apparatus processes and packages the molecules,
ready for release.
7. The molecules are `pinched off' in vesicles from the Golgi
apparatus and moves towards the cell surface membrane.
8. Vesicles fuse with the cell surface membrane and the
membrane opens to release the molecules outside- this is
exocytosis.
Cytoskeleton
The cytoskeleton is made up of...
1. Microfilaments
2. Microtubules
3. Intermediate filaments
Its function is to...
1. Keep the cells shape and strength and stability
2. Whole cell movement
3.…read more

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No membrane bound Membrane bound
organelles organelles (mitochondria,
chloroplast etc.…read more

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Cell Membrane
Cholesterol- Gives the membrane stability by sitting between the
fatty acid tails and therefore making the barrier more complete,
preventing molecules like water and ions passing through the
membrane.
Glycolipids- Phospholipid molecules that have a carbohydrate
part attached. They are used for cell signaling, cell surface
antigens and cell adhesion.
Glycoproteins- Protein molecules with a carbohydrate attached:
Act as antigens
Enable the identification of cells as self or non-self
Used in cell signaling
Act as receptors or binding sites for hormones.…read more

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Channel proteins- Allow the movement of some substances,
such as the large molecule sugar, into and out of the cell as they
can't travel directly through the cell surface membrane.
Carrier proteins- Actively move substances across the cell
surface membrane.
Function of membranes:
Separate cell contents from outside environment
Cell recognition and signaling
Holding the components of some metabolic pathways in place
Regulating the transports of materials into or out of the cell
Allow compartmentalisation
Isolate harmful substances (e.g.…read more

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Cell communication and signaling
Most messenger molecules are unable to directly cross
the membrane and must bind to the membrane bound
receptors in order to communicate with a cell.
Some integral proteins are receptors for hormones and
neurotransmitters.
Different cells have specific receptors depending on the
role in our body.
Via receptors and complementary shaped molecules on
the target cell.…read more

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