Biology 2.1 Microscopes (Updated)

Question 1

What is the definition of magnification and resolution

Answer 1

Magnification: the number of times larger an image is compared to its actual size
Resolution: the ability to distinguish between two points

Question 2

What are the pros of an optical microscope

Answer 2

•Relatively cheap
•easy to use and portable
•can view living species

Question 3

What are the cons of an optical microscope

Answer 3

•it use light which has a wavelength of 400-700nm so objects smaller are unclear or appear as one, so microscopes have a low magnification and resolution.

Question 4

How do you use a Transmission electron microscope

Answer 4

1. Fix specimen by staining with heavy metals
2. The microscope then use electromagnets to focus a beam of electrons onto a specimen, less electrons will pass through the thicker parts of the specimen and onto the photographic plate beneath the specimen.
3. Therefore producing a 2D image black and white image with darker areas representing thicker regions.

Question 5

How do you use a scanning electron microscope

Answer 5

1.coat specimen with fine film
2.Electrons are shot back and forth on a sample and reflect in different directions due to bumps on surface
3.The computer analyses results and produces a 3D image of specimen
4. The computer then adds false colour to the image.

Question 6

What are the pros of an electron microscope

Answer 6

1.Can view details of organelles which will help scientists relate their structure to their function

Question 7

What is an artefact and some examples

Answer 7

a structural detail created when processing the specimen that isn’t actually a detail of the specimen.
For e.g.:
-a broken membrane
-bubbles
-mesosomes

Question 8

What are the different types of preparations of slides.

Answer 8

Dry mount, Wet mount, Squash slide, Smear slide

Question 9

What is a dry mount and examples

Answer 9

Put a solid specimen on a slide and cover with cover slip using a mounted needle. Then view under a microscope.
Examples are: hair, muscle tissue etc..

Question 10

What is a wet mount and examples

Answer 10

Put specimen in liquid and add a cover slip at an angles using a mounted needle to avoid bubbles.
Examples: aquatic and living organisms

Question 11

What is a squash slide and examples

Answer 11

Add liquid and cover slip and press down on cover slip to squash the slide.

Examples: Root tip squashes- to look at cell division

Question 12

What is a smear slide and examples

Answer 12

Drop liquid on one end of the slide and use cover slip to smear it down to the over end

Examples: blood smear

Question 13

What is an eyepiece graticule and why does it have to be calibrated

Answer 13

An eyepiece graticule is a disc with a small ruler which is added to a microscope and can be used to measure the size of a specimen.
The length is arbitrary as it changes at different magnifications so at different magnifications it needs to be calibrated using a stage micrometer.

Question 14

How do you calibrate an eyepiece graticule

Answer 14

Add the stage micrometer and look down the microscope and rotate the microscope until the eyepiece graticule is aligned. Then count the number of eyepiece division which is equivalent to the stage micrometer divisions and find out the actual length of this using the stage micrometer. Divide this length by the number of eyepiece graticule divisions to get the length of one division of the eyepiece graticule.

Question 15

What is the typical magnification of an eyepiece lense?

Answer 15

x10

Question 16

What is ultrastructure?

Answer 16

The detailed structure of cells visible only with an electron microscope

Question 17

Why do cells need to be stained?

Answer 17

-To make the cell/organelles visible
-Helps increase contrast