1. Microscopy & Cell Theory

2. Bell ringer Electron microscope Reminder: Project for Tues, 8/28
Produce an annotated poster displaying an animal or a plant cell. Your cell must be hand – drawn!
(Organelles to include as appropriate: Cell surface membrane, Nucleus, nuclear envelope, nucleolus, Endoplasmic reticulum (smooth and rough), Golgi apparatus (Golgi complex, Golgi body), Mitochondria (including small circular DNA), Ribosomes (differentiate 80S and 70S), Lysosomes, Centrioles + Microtubule, Chloroplasts (including small circular DNA), Cell wall and plasmodesmata, Large permanent vacuole and tonoplast)

3. Learning objectives
explain and distinguish between resolution and magnifcation, with reference to light microscopy and electron microscopy
calculate the linear magnifcations of drawings, photomicrographs and electron micrographs
use an eyepiece graticule and stage micrometer scale to measure cells and be familiar with units (millimetre, micrometre, nanometre) used in cell studies
calculate actual sizes of specimens from drawings, photomicrographs and electron micrographs
describe and interpret electron micrographs and drawings of typical animal and plant cells as seen with the electron microscope

4. Scanning Electron Microscope (SEM)
Transmission Electron Microscope (TEM)
Electrons don't pass through the specimen.
They bounce off the specimen.
3D view
Magnification is x
Electron beam passes through a thin sample
Electrons pass through the denser parts less easily – contrast
Image is 2D
Magnification is x

5. Electron microscope: advantages and disadvantages
Resolution is 0.1nm
Detailed images or organelles
3D images-shows contours (SEM)
Disadvantages:
Electron beams deflected by air molecules - vacuum needed.
Expensive
Skill & training needed

6. Coloured electron micrographs
Electron micrographs are always black, white & grey when they are produced
Colours can be added afterwards using computer software=false colour electron micrographs

7. Development of Cell Theory
SCHWANN
HOOKE
SCHLEIDEN
1665: pore-like structures “cells”
All animal tissues are composed of cells.
VIRCHOW
All cells must arise from preexisting cells.
All plants are made of cells

8. Cell theory All living beings are made up of cells.
Cell is the most basic unit of life.
All cells must come from pre-existing cells.

9. Investigating cell make-up
Cells are very small, therefore we need to produce images that are enlarged & more detailed to study them
Light microscope improvements
Electron microscopes
Investigating chemical reactions occurring in different parts of the cell

10. Magnification vs. Resolution
Magnification is how much bigger a sample appears to be under the microscope than it is in real life.
Resolution is the ability to distinguish between two points on an image - the amount of detail.
e.g. if two objects are less than 200nm apart they are seen as one object.
Total Magnification = objective magnification x eyepiece magnification

13. Magnification
Resolution

14. Magnification
Resolution
Increasing the magnification does not increase the resolution of the image!!

15. Light Microscope Resolution: 200nm Magnification: x4, x10, x40
Invention of microscope
Light Microscope
Resolution: 200nm
Therefore any images closer together than 200nm will be seen as 1 object
Due to magnitude of the wavelength of light
2 objects can only be seen if light can pass between them
Human eye resolution = 100μm
Magnification: x4, x10, x40
x100 (oil immersion)

16. Add labels to your diagrams
Arm
Base
Body tube
Coarse adjustment screw
Condenser lens
Eye
Eyepiece
Fine adjustment screw
High power objective lens
Lamp
Low power objective lens
Mirror
Objective lens
Specimen
Stage

18. Light passes from the bulb, then through the specimen
Beam of light is focused through the objective lens, then through the eyepiece lens
X4, X10, X40, X100 Objective lenses
The eyepiece lens then magnifies image again by x10
Therefore total magnifications of x40, x100, x400, x1000
MAX light microscope magnification =x1500 (x15 eyepiece x100 objective lens)

19. Using a Microscope Start on the lowest magnification
Don’t use the coarse adjustment knob on high magnification…you’ll break the slide!!!
Place slide on stage and lock clips
Adjust light source (if it’s a mirror…don’t stand in front of it!)
Use fine adjustment to focus

20. Home Learning
Preparing a slide Info and question sheet

21. Working out magnification
Magnification = Observed size of the image
actual size
Remember to convert values to the same unit first!

22. Complete practice sheet on magnification calculations
Measuring cells
Complete practice sheet on magnification calculations
Work through pages 8 – 9, take notes on how to measure cells, calculate magnification of a photograph or image, and calculating magnification from a scale bar.

23. Electron micrographs
Name the structures

24. Nucleus with Nucleolus

25. Golgi apparatus wit Vesicles

26. Mitochondrion

27. Chloroplast

28. Endoplasmic reticulum

29. Lysosomes

30. Vacuoles

31. Bacterium with flagella

32. Task
In pairs look at electron micrographs of cells and identify as many organelles as possible.
Look at at least two different micrographs

33. Summary Quiz
Complete the Quiz on calculations and organelle identifications using micrographs. (15min)

34. Can you guess what it is?
A fly!!

35. Can you guess what it is?
Carpet!

36. Can you guess what it is?
A feather!!

37. Can you guess what it is?
A flower!!

38. Can you guess what it is?
A grape!

39. Can you guess what it is?
Snowflakes!

40. Things found in your nose!
Can you guess what it is?
Things found in your nose!

41. Can you guess what it is?
Seaweed!

42. Can you guess what it is?
Skin!

43. Swine Flu’! (don’t worry it’s a picture!)
Can you guess what it is?
Swine Flu’! (don’t worry it’s a picture!)

44. Can you guess what it is?
Velcro!

45. Can you guess what it is?
Vitamin C!

46. The leg of a Water Boatman!
Can you guess what it is?
The leg of a Water Boatman!