1. Practical Microscopy

2. Size matters:How large are cells?
Let's put things into perspective....

3. Phospholipid membrane
Organism
Size
Prokaryotic cell
1 – 10 μm
Animal Cell
10 – 30 μm
Plant Cell
10 – 100 μm
Virus
< 100 ηm
DNA molecule
2 ηm
Phospholipid membrane
10 ηm

4. What can you visualise with the naked eye?

5. What can you visualise with the naked eye?
0.1 mm
(100 μm) .

6. Magnification
X400 –
X1500

7. Magnification Electron microscope: X 1500 –
X500,000 (and incredible detail [resolution])

8. Magnification: Scanning Tunnelling microscope
Resolution: 0.1 ηm:
can show atom – atom!

9. Biggest and smallest cells
Human egg: 130 μm
Human sperm: 60 x 5 μm
Some neurons can be 1 m long!

10. You should be able to identify
Eye piece (X 10 magnification)
Light source
Objective lenses (X 4, X10, X40)
Coarse Adjustment knob
Fine adjustment knob

11. Body tube Eye Piece Arm 4x Objective 10x Objective Stage 40x Objective
Revolving nosepiece
Arm
4x Objective
10x Objective
Stage
40x Objective
Stage Clips
Coarse Adjustment
Diaphragm
Fine Adjustment
Light source
Base

12. Guidelines for working with microscopes
ALWAYS carry a microscope with BOTH hands The Three-Step Method 1. Use the scanning objective (red X 4) and bring it into focus using the LARGE KNOB (coarse adjustment) 2. Switch to low power (yellow X 10) and refocus using the SMALL KNOB – re-centre if necessary. 3. Switch to high power (blue X 40) and
ONLY focus
with the small knob
(fine adjustment)

13. Calculating magnification/image size/actual size
The ‘I am’
triangle

14. Clean Up, Clean Up, Everybody Clean Up!
When you are finished with the microscopes, should store them appropriately:
Set to the lowest objective (4X).
Light intensity to lowest setting.
Power off.
Mechanical stage set such that the mechanism does not poke a hole through the custom covers
Stage down
Cord wrapped  (gently around the scope is sufficient - nothing fancy). 
Cover in place
Of course, the stage should be free from dirt, water, and solutions.  However, you should not attempt to clean the optics.  Report dirty oculars or objectives

15. What are you looking at? Animal cells with/without methylene blue
Plant cells (onion and elodea) with/ without methylene blue
Plant cells with/without iodine
Protists (paramecium sample)
Protists (pond water)

16. Homework for Week 3 Organelle identification
Practice questions on organelle size
Practice questions on magnification
Practice questions on cell organelles (you will have a quiz on this next week!)