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AS Biology
Unit 1- Cells, Exchange
and Transport (F211)




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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…

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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…

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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…

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6. 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.…

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No membrane bound Membrane bound
organelles organelles (mitochondria,
chloroplast etc.)
Peptidoglycan cell wall Cellulose cell wall
Spiral flagella Waved flagella
Smaller ribosomes Larger ribosomes
Single-loop chromosomes Linear chromosomes
Single-celled One or more cell
Contains plasmids Do not contain plasmids




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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…

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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…

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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.…

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