Lesson 24 - Cells - Microscopes

Question 1

Name some parts of an optical light microscope

Answer 1

Nosepiece
Arm
Coarse focus
Fine focus
Stage
Stage clip
Rack stop
Light source
Condenser
Base
Eyepiece
Objective lens

Question 2

what is the formula for magnification?

Answer 2

size of image/size of real object

Question 3

what is the epiece graticule on a microscope used for?

Answer 3

• to measure the size of cells
  or objects
• Not a specific scale - just measured in eyepiece units (e.p.u.)

Question 4

how to

Answer 4

1) Your drawing and its label lines must be done with a really sharp pencil (not a pen).
2) It should take up at least half the page.
3) Lines nmust be clear and continuous – not ragged or broken – and no shading/colouring is allowed.
4) Ensure the proportions are correct, i.e. different areas are the right size relative to each other, and that your drawing is a true likeness of the specimen that you are drawing.
5) Label all the different features that you have shown, writing the words in pencil or pen.
6) Rule the label lines (in pencil). Don’t let the label lines cross each other and do not write on the label lines.
7) Make sure the label lines touch the part you are labelling.

Question 5

describe how you would make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells using an (optical) light microscope

Answer 5

1) add a drop of water to (glass) slide
2) obtain thin section of plant tissue, and place on slide/float on drop of water
3) stain with iodine in potassium iodide
4) lower cover slip using mounted needle

Question 6

what are the possible labels you could use when drawing a human blood smear?

Answer 6

Leucocyte (white blood cell)
Erythrocyte (red blood cell)
Nucleus
Lobed nucleus
Cell membrane
Cytoplasm

Question 7

what are the possible annotations you could use when drawing a human blood smear?

Answer 7

• Red blood cells contain haemoglobin to bind oxygen
• nucleus contains chromosomes made of DNA
• Composed of phospholipid and proteins
• No nucleus present in red blood cells
• Biconcave shape for larger surface area

Question 8

how many meters are each of these?
- Decimetre (dm)
- Centimetre (cm)
- Millimetre (mm)
- Micrometre (µm)
- Nanometre (nm)

Answer 8

Decimetre - 0.1m
Centimetre - 0.01
Millimetre - 0.001
Micrometre - 0.000 001
Nanometre - 0.000 000 001

Question 9

how to get from cm to mm

Answer 9

x10

Question 10

how to get from mm to µm

Answer 10

x1000

Question 11

how to get from µm to nm

Answer 11

x1000

Question 12

what are the 2 types of microscopes?

Answer 12

light mocroscopes
electron microscopes

Question 13

what is the magnification of an eyepiece lens?

Answer 13

x10

Question 14

what is the total magnification of a x10 eyepiece lens an a x30 magnification lens?

Answer 14

x300

Question 15

how do light microscopes work?

Answer 15

• Pairs of convex glasses used
• Uses light rays – light rays have relatively long wavelengths – therefore a light microscope can only distinguish between two objects 0.2 µm or further apart

Question 16

what is the difference between magnification and resolution?

Answer 16

Magnification = the degree to which the size of an image is larger than the object itself.
Resolution (or resolving power) = The minimum distance apart that 2 objects can be in order for them to appear as separate items. The higher the resolution, the greater the detail you can see.

Question 17

what can you see inside a cell with a light vs an electron microscope?

Answer 17

Using a light microscope, it is possible to see the nucleus and nucleolus in a typical animal cell – mitochondria may be visible.
Using an electron microscope you can see much greater detail, e.g. ribosomes.

Question 18

magnification (light microscopes vs electron microscopes)

Answer 18

• Light microscopes can magnify an image by 2000 times (ours do up to 400)
• Electron microscopes can magnify over a million times (and some research instruments achieve over ten million)