2.1 - Cell Structure

Question 1

Define MAGNIFICATION.

Answer 1

How much bigger an image appears compared with the original object.

Question 2

Define RESOLUTION.

Answer 2

The ability of an optical instrument to see or produce an image that shows fine detail clearly - distinguishing two objects as separate from each other.

Question 3

Give 4 benefits of OPTICAL MICROSCOPES.

Answer 3

1. Relatively cheap
2. Easy to use
3. Portable and able to used in the field as well as in laboratories
4. Able to be used to study whole LIVING specimens.

Question 4

What’s the common max magnification of optical microscopes?

Answer 4

x1500 (some x2000)

Question 5

What’s the resolution of optical microscopes?

Answer 5

200 nm

Question 6

What is the formula for calculating TOTAL magnification?

Answer 6

total magnification = magnifying power of the OBJECTIVE lens x magnifying power of the EYEPIECE lens

Question 7

What is a photomicrograph?

Answer 7

A photograph of the image seen using an optical microscope.

Question 8

How do laser scanning microscopes work?

Answer 8

They use laser light to scan an object point by point and assemble, by computer, the pixel information into one image, displayed on a computer screen.

Question 9

Give 4 uses/benefits of laser scanning microscopes.

Answer 9

1. Images are high resolution and show high contrast.
2. The microscopes have depth selectivity and can focus on structures at different depths within a specimen, so can be used to clearly observe whole living specimens, as well as cells.
3. They are used in the medical profession in order to give a swift diagnosis and earlier, more effective treatment.
4. Used in many branches of biological research.

Question 10

What is the resolution of electron microscopes?

Answer 10

0.004 nm

Question 11

How do electron microscopes work?

Answer 11

The electrons are fired from a cathode and focused, by magnets, on to a screen or photographic plate.

Question 12

How do Transmission Electron Microscopes (TEM) work?

Answer 12

1. The specimen has to be chemically fixed by being dehydrated and stained.
2. The beam of electrons passes through the specimen,