Module 1- Cells- 1.1.1 Cell Structure

a + c)
Light Microscope-
x1500 magnification, 200nm resolution,
These are used and found in school laboratories as well as some conventional use. They are used by staining the sample with a dye and then placed underneath the lenses.
Transmission Electron Microscope (TEM)-
x500,000 magnification, 0.2nm resolution,
This microscope is much more powerful than the light microscope. It produces a 2D image as electrons pass through a thin sample, moving through the denser parts of the sample much less easily than the less denser parts. A false colour is applied afterwards.
Scanning Electron Microscope (SEM)-
x100,000 magnification, 0.2nm resolution,
Again, this microscope is much more powerful than the light microscope, but it doesn't have such a great magnification as the TEM. It does however produce 3D images. The sample is coated in a gold stain and the electrons bounce off the surface revealing the contours of the sample.

b)
Magnification- the number of times greater an image is than the object.
Resolution- the ability to distinguish two separate points that are distinct from each other

d)
Magnification= Image/Actual. Remember it is IAM (like I AM and IAMS cat).

f)
Nucleus- houses genetic information and proteins, with DNA found in chromatin (when stained shown in dark patches)
Nucleolus- creates RNA and ribosomes which pass into the cytoplasm and helps create proteins. It is a dense spherical structure inside the nucleus.
Nuclear envelope- structure of two membranes with fluid between them that contain pores that are big enough for relatively large molecules to pass through.
Rough Endoplasmic Reticulum (RER)- Transports proteins created by the nucleus. Flattened membrane bound sacs covered in ribosomes.
Smooth Endoplasmic Reticulum (SER)- used to create lipids. Again it is a flattened membrane bound sac but it is not covered in ribosomes.
Golgi Apparatus- Membrane bound flattened sacs. Receives proteins from the RER, modifies them and packages them in vesicles.
Ribosomes- found on the outside of the RER. They are the site of protein synthesis (amino acids made into proteins).
Mitochondria- spherical, with two membranes. Produce ATP from which energy is produced.
Lysosomes- spherical sacs made of one membrane. Contain powerful digestive enzymes used to break down materials (e.g. in white blood cells to break down microorganisms or on the head of a sperm to break down the material surrounding the egg.
Chloroplasts- found only in plant cells. Contain chlorophyll and are the site of photosynthesis.
Plasma membrane- used to separate cell contents from cytoplasm, separating cell contents, cell recognition and signalling. (more in cell membranes topic)
Centrioles- pull chromosomes apart during nuclear division. Only found in animal cells, not in plant cells.
Flagella and Cilia- Used to waft or transport materials within or outside of cells.

g)
Protein Secretion
- mRNA copy of the gene created in the nucleus.
-this leaves the nucleus through the nuclear pore.
-attaches to a ribosome on the RER and protein is created.
-the protein is pinched off into a vesicle.
-vesicle travels to the golgi apparatus and fuses with it.
-the protein is modified and repackaged into another vesicle before being released.
-the vesicle travels to and fuses with the cell surface membrane.
-the molecule is released from the cell.

h)
The Cytoskeleton
- Providing Mechanical Stability
network of protein fibres, keep the shape and the internal framework stable
-Aiding Transport Within Cells
microtubules move chromosomes during mitosis and meiosis. Filaments move organelles. Vesicles moved between organelles.
-Enables Cell Movement
microtubules move organisms through a liquid or waft liquid past a cell.

	Created by Laura Perry over 9 years ago

A Levels Biology (AS Biology) Note on OCR Biology- AS Level- Module 1 Cells, created by Laura Perry on 30/03/2015.