1. What is the actual size of this?

2. 1.1 Introduction to cells Nature of science: Understandings:
Applications:
Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae.
Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.
Use of stem cells to treat Stargardt’s disease and one other named condition.
Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues.
Understanding:
Understandings:
According to the cell theory, living organisms are composed of cells.
Organisms consisting of only one cell carry out all functions of life in that cell.
Surface area to volume ratio is important in the limitation of cell size.
Multicellular organisms have properties that emerge from the interaction of
their cellular components.
Specialized tissues can develop by cell differentiation in multicellular
organisms.
Differentiation involves the expression of some genes and not others in a
cell’s genome.
The capacity of stem cells to divide and differentiate along different
pathways is necessary in embryonic
Skills:
Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)
Nature of science:
Looking for trends and discrepancies—although most organisms conform to cell theory, there are exceptions. (3.1)
Ethical implications of research—research involving stem cells is growing in importance and raises ethical issues. (4.5)

3. Magnification Calculate true size, image size, and magnification
Make unit conversions

4. Magnification
Micrographs often have the magnification or scale bars to allow calculation of the actual size of specimens.
x400
4.55μm

5. Magnification
In this exercise you will calculate the
magnification and/or true size of the
following: 1 2 3 4 5 8 6 7 10 9

6. Before we begin:
Note:
Numbers written like this: 1.26 x 105 mean you move the decimal point to the right. In this case you move it 5 times:
1.26 x 105 = .

7. Before we begin:
Note:
Numbers written like this: 1.26 x 10-5 mean you move the decimal point to the left. In this case you move it 5 times:
1.26 x 10-5 =

8. Have a go at these: 14500.0 1.45 x 104 = 0.37 x 107 = 86.41 x 10-3 =
0.0265

9. Units Unit How many millimeters Millimeter (mm) 1 mm Micrometer (μm)
Nanometer (nm) mm

10. Conversions
mm into μm (x 1000) μm into nm (x 1000) 32.5 mm is how many μm?
32 500

11. Calculations… Size of image (I) True size (T) Magnification (M)
Write the equations for each
Size of image (I)
True size
(T)
Magnification
(M)

12. Figure 5.1 Paramecium caudatum
Find the true size (T)
x600

13. Figure 5.1 Paramecium caudatum
Measured length = 142mm
142 ÷ 600 = 0.237mm
0.237mm = 237μm
x600

14. Figure chloroplasts
x9000

15. Figure chloroplasts
Mean measured length of the four largest chloroplasts = 39.25mm
39.25 ÷ 9000 = mm
0.0044mm = 4.4μm
x9000

16. Figure 5.3a bacterium (actual size = 0.002mm)
Calculate the magnification (M)
Measured length = 128mm
128 ÷ 0.002mm = magnification
Magnification = x64000

17. Figure 5.4 seven week human embryo

18. Figure 5.4 seven week human embryo
If you have a scale bar…
Measure the actual length of the scale bar (25mm) and divide by the length it represents
Magnification = 25 ÷ 10 = x2.5

19. Figure 5.5 head of a fruit fly

20. Figure 5.5 head of a fruit fly
A length of the scale bar mm
Magnification = 12.5 ÷ 0.2 = x62.5

21. Figure pollen grain

22. Figure pollen grain
(a) Measure the actual length of the scale bar and divide by the length it represents
Magnification = 25 ÷ 0.02 = x1250
(b) Image size = 47mm. What is the true size?
(c) 47 ÷ 1250 = mm
0.0376mm = 37.6μm

23. Figure 5.7 red blood cells in an arteriole

24. Figure 5.7 red blood cells in an arteriole
Measured length of scale bar = 30mm
Magnification = 30 ÷ 0.01 = x3000
Diameter = 25mm
Actual diameter = 25 ÷ 3000 = mm
0.0083mm = 8.3μm

25. Figure 5.8 a mitochondrion

26. Figure 5.8 a mitochondrion
Measured length of scale bar = 30mm
Magnification = 30 ÷ = x15000
Measured width = 34mm
Actual width = 34 ÷ = mm
0.0023mm = 2.3μm

27. Figure 5.9 bacteriophage [a type of virus]

28. Figure 5.9 bacteriophage [a type of virus]
Measured length of phage = 29mm
Magnification = 29 ÷ = what about in standard form?
Magnification = 1.45 x 105

29. Magnification
The resolving power of the unaided eye is approximately 0.1mm
The maximum useful magnification of light microscope is around x1500
Plant and animal cells typically measure around 20µm
Many organelles are as small as 25nm – beyond the resolving power of the light microscope [wavelength of light is 500nm approx]
Wavelength of electron beam is 0.005nm
Maximum resolving power of the electron microscope is 0.2nm