1. CELLS AND SIZES (2.1)

2. Can you arrange these items from biggest to smallest?
Virus
Atom
Plant cell
Bacteria
Human
DNA
Frog egg
Chicken egg
Click the next slide to see the answer!

3. Human
Chicken egg
Frog egg
Plant cell
Bacteria
Virus
DNA
Atom

4. 1. molecules (1 nanometer = 1 nm). 2. cell membrane thickness (10 nm).
COMPARE THE RELATIVE SIZES OF MOLECULES, CELL MEMBRANE THICKNESS, VIRUSES, BACTERIA, ORGANELLES AND CELLS (2.1.4)
Relative sizes:
1. molecules (1 nanometer = 1 nm).
2. cell membrane thickness (10 nm).
3. virus (100 nm).
4. bacteria (1micrometer or 1 μm).
5. organelles (less 10μm).
6. cells (<100 μm – plants cells are larger than animal cells)

5. RECAP: SI UNITS OF MEASUREMENT

6. PRACTICE CONVERSIONS! How many millimeters in a meter?
How many micrometers in a millimeter?
How many nanometers in a micrometer?
How many nanometers in a millimeter?
Convert 50 μm to millimeters.
Convert 100 nm to micrometers.
Convert 10 mm to nanometers.
Convert 20 mm to micrometers.
More practice here:

7. ANSWERS! How many millimeters in a meter? 1000
How many micrometers in a millimeter? 1000
How many nanometers in a micrometer? 1000
How many nanometers in a millimeter?
Convert 50 μm to millimeters mm
Convert 100 nm to micrometers. 0.1 μm
Convert 10 mm to nanometers nm
Convert 20 mm to micrometers μm

8. What is the ACTUAL size of this stoma?
CALCULATE THE MAGNIFICATION OF DRAWINGS AND THE ACTUAL SIZE OF SPECIMENS IN IMAGES OF KNOWN MAGNIFICATION (2.1.5)
What is the ACTUAL size of this stoma?

9. Method #1. Using Scale Bars
First calculate the scale on the scale bar:
Scale length = μm
Ruler length mm
= 1.33μm per mm
Then measure the image with the ruler:
x μm is 60 mm on the image
Now calculate the true length:
1.33 x = μm
(scale) (image length)
TIP! Always measure in mm – it will make your life easier, trust me!

10. What is the ACTUAL diameter of this egg cell?

11. What is the ACTUAL size of this bacterial cell?
CALCULATE THE MAGNIFICATION OF DRAWINGS AND THE ACTUAL SIZE OF SPECIMENS IN IMAGES OF KNOWN MAGNIFICATION (2.1.5)
What is the ACTUAL size of this bacterial cell?

12. Method #2. Using Magnification MEASURE the length of the cell 80 mm
(remember always use mm!)
DIVIDE by the magnification given
80mm = mm
90 000
CONVERT to a whole number = 890 nm
Remember to: MEASURE
DIVIDE
CONVERT

13. FIND THE REAL SIZE OF THESE CELLS USING THE MAGNIFICATION:

14. What is the MAGNIFICATION of this plant cell image?
CALCULATE THE MAGNIFICATION OF DRAWINGS AND THE ACTUAL SIZE OF SPECIMENS IN IMAGES OF KNOWN MAGNIFICATION (2.1.5)
What is the MAGNIFICATION of this plant cell image?

15. MEASURE the length of the scale bar
CALCULATE THE MAGNIFICATION OF DRAWINGS AND THE ACTUAL SIZE OF SPECIMENS IN IMAGES OF KNOWN MAGNIFICATION (2.1.5)
MEASURE the length of the scale bar
20 mm
(remember always use mm!)
CONVERT to scale bar units
1 mm = μm
DIVIDE by the scale bar label
μm = x
10 μm
Remember to: MEASURE
CONVERT
DIVIDE

17. More Practice! Remember to: MEASURE DIVIDE CONVERT MEASURE = 250 mm
A student views an image of a cell magnified 350 times. The image is 250 mm long. Calculate the actual length of the sample in the image.
Remember to: MEASURE
DIVIDE
CONVERT
MEASURE = 250 mm
DIVIDE = 250 mm/350 x
= mm
CONVERT = 714 μm

18. More Practice! Remember to: MEASURE CONVERT DIVIDE MEASURE = 75 mm
A sperm cell as a tail of 50µm long. A student draws it 75 mm long. Calculate the magnification.
Remember to: MEASURE
CONVERT
DIVIDE
MEASURE = 75 mm
CONVERT = μm
DIVIDE = μm/ 50 μm
= x