Microscopes

Question 1

How do you calculate magnification?

Question 2

How do you go from cm to Micrometers?

Answer 2

x 10000

Question 3

What is resolution?

Answer 3

How well two points that are close together can be told apart.

Question 4

How does an optic microscope create an image?

Answer 4

Using light.

Question 5

How does an electron microscope create an image?

Answer 5

Using electron beams.

Question 6

What are the differences between an optical and electron microscope?

Answer 6

Optical microscopes have a lower resolution and magnification.
When using an electron microscope the sample must be dead because it requires a vacuum.

Question 7

How does a TEM create an image?

Answer 7

A beam of electrons is focused on the sample and the parts that absorb more electrons appear darker in the image.

Question 8

How does an SEM create an image?

Answer 8

A beam of electrons is scattered across the surface of the specimen and those are gathered to form an image.

Question 9

What are the differences between a TEM and an SEM?

Answer 9

A TEM has a higher resolution and magnification compared to a SEM. The sample used in a TEM must be thin and in an SEM it doesn’t matter. TEMs produce 2D, black-and-white images. SEMs produced 3D-coloured images.

Question 10

What are the steps in cell fractionation?

Answer 10

1. Homogenisation
2. Filtration
3. Ultracentrifugation

Question 11

What happens in homogenization?

Answer 11

The cells are placed in an isotonic, buffered and cold solution and then placed in a blender. This breaks the cell membranes of the cell and releases the organelles.

Question 12

Why must the solution be isotonic?

Answer 12

To prevent water from being drawn into the organelles via osmosis and damaging them.

Question 13

Why must the solution be ice cold?

Answer 13

to reduce enzyme activity that leads to the breakdown of organelles.

Question 14

Why must the solution be buffered?

Answer 14

To maintain the pH.

Question 15

What happens infiltration?

Answer 15

The homogenate is filtered using gauze.

Question 16

Why must the homogenate be filtered?

Answer 16

To remove any unbroken cells and tissue debris.

Question 17

What happens in ultracentrifugation?

Answer 17

The homogenate is placed inside the centrifuge and spun at low speeds to remove denser organelles like the nucleus. These organelles form a layer at the bottom of the tube that can be collected as a pellet. The supernatant is then spun in the centrifuge at increasing speeds to remove less dense organelles like the mitochondria and the ribosomes.