1. Prokaryotic and Eukaryotic cells
LO: to be able to label a diagram of a prokaryotic cell.
:to know the differences between prokaryotic and eukaryotic cells.
:to understand how an optical (light) microscope works.
:to understand in detail some eukaryotic organelles (plasma membrane and microvilli; nucleus).

2. Draw a cell!

3. Prokaryotic and Eukaryotic cells
Prokaryotic cells
Simple
Bacterial
No membrane bound organelles
Eukaryotic
Complex
All other cells
Membrane bound organelles

4. Prokaryotic cells DNA not associated with protein. DNA is circular.
Contain plasmids.
Cell wall made from peptidoglycan.
Capsule or slime layer.
Have 70S ribosomes.
May possess flagella.
May have pili.

5. Optical microscope Optical microscopes are compound microscopes
Occular lens
Optical lens
Light passes through the specimen.
Different areas absorb different amounts (and wavelengths) of light.
Dark areas that absorb a lot of light are called optically dense regions.

6. Optical microscope
The lenses refract light and so cause the image to appear larger.
The resolution is limited to the wavelength of light.
Objects smaller than 0.2µm can not be resolved, and so seen, by a light microscope.
NB. Take care with language- do not talk about the wavelength of the microscope but the wavelength of light!

7. Definitions Magnification- making an object appear larger than it is.
Resolution- ability of an instrument to distinguish between 2 points that are close together. Allows for more detail.
Micrometre- µm 1/1000 mm or 1/ m

8. Summary of differences!
Prokaryotic Cells
Eukaryotic cells
small cells (< 5 µm)
larger cells (> 10 µm)
always unicellular
often multicellular
no nucleus or any membrane-bound organelles
always have nucleus and other membrane-bound organelles
DNA is circular, without proteins
DNA is linear and associated with proteins to form chromatin
ribosomes are small (70S)
ribosomes are large (80S)
no cytoskeleton
always has a cytoskeleton
cell division is by binary fission
cell division is by mitosis or meiosis
reproduction is always asexual
reproduction is asexual or sexual

9. Quick quiz! Take your set of cards and find the 3 black cards.
Arrange the features of each type of cell around the correct card.
First team to get it right wins!

10. Looking at prokaryotic cells.
Must use aseptic technique
Disinfect bench
Wear plastic apron
Work near a lit bunsen burner
Flame loop
Flame mouth of culture bottle before and after removing culture sample
Dispose of slides in a beaker of disinfectant
Sterilise bench when finished
Place all possible contaminants in an autoclave bag