The Cell & Microscrope

Question 1

What is the classical cell theory?

Answer 1

1. All living organisms have one or more cells.
2. Cells are the fundamental unit of life.
3. All cells come from pre-existing cells.

Question 2

What is the name given to the hereditary information contained within a cell?

Answer 2

DNA

Question 3

What are the ocular lenses?

Answer 3

Ocular lenses (or eyepiece) are what you look through to see the image of your specimen.

Question 4

By how much does the ocular lens increase magnification?

Answer 4

10x

Question 5

What is the rotating nosepiece?

Answer 5

It is the rotating part of the microscope at the bottom of the body tubes that hold the objective lenses.

Question 6

What are objective lenses?

Answer 6

The microscope may have 2-3 objective lenses varying in length. Each lenses have a different magnification, the longest one typically having the greatest magnification.

Question 7

What is the coarse focus knob?

Answer 7

A large round knob on the side of the microscope used to for rough focusing of the specimen; it may move either the stage or the upper part of the microscope.

Question 8

What is the fine focus knob?

Answer 8

A small round knob on the side of the microscope used to fine tune/sharpen the focus of your specimen.

Question 9

What is used first; the coarse or fine focus knob?

Answer 9

The coarse focus knob, then the fine focus knob.

Question 10

What is the “aperture?”

Answer 10

The hole in the stage that allows light through for better viewing of the specimen.

Question 11

What is the “diaphragm?”

Answer 11

A disc with 5 holes of varying diameter controlling the amount of light that goes through.

Question 12

Define magnification.

Answer 12

The ratio of enlargement or reduction of an image.

Question 13

Define resolution.

Answer 13

The ability of a lens system to show fine details of the object being observed.

Question 14

How do you convert mm into micrometres? Then to nanometers?

Answer 14

Multiply by 1000. Then 1000 again.

Question 15

Define “Field of View.”

Answer 15

The area visible to you when looking through the eyepiece of the microscope.

Question 16

Name the technologies to improve microscopy.

Answer 16

Advanced staining techniques, gram staining, lighting techniques, electron microscope.

Question 17

What does crystal violet (purple) stain?

Answer 17

The cell walls.

Question 18

What does methylene blue stain?

Answer 18

The nucleus.

Question 19

What does haematoxylin (blue) stain?

Answer 19

Chromosomes to show mitosis/meiosis.

Question 20

What is gram staining?

Answer 20

A method of differentiating bacterial species into two large groups based on the physical and chemical properties of their cell walls - gram positive and gram negative.

Question 21

Bacteria that are stained with crystal violet will either stain purple or pink. What’s the difference between the two?

Answer 21

• Purple bacteria are called “gram positive” and have a thick layer of peptidoglycan in their cell wall.
• Pink bacteria are called “gram negative” and only have a thin layer of peptidoglycan

Pep-tye-doe-glaican.

Question 22

What is phase contrast microscopy?

Answer 22

It is a contrast-enhancing optical technique used to create high-contrast images of transparent specimens.

Question 23

What is an advantage of phase contrast microscopy?

Answer 23

It does not kill, fix or stain living cells, therefow allowing the observation of biological processes.

Question 24

What makes electron microscopes different from light and glass lense microscopes?

Answer 24

They use a high energy beam of electrons rather than light which increases resolution to a limit of 0.2µm.

Question 25

What are the types of electron microscopes?

Answer 25

1. Scanning electron microscopes (SEM) produce images by scanning the surface of the viewed specimen.
2. Transmission electron microscopes (TEM) transmit electrons through the specimen, producing an images of the internal structure of cells.

Question 26

How do light microscopes work?

Answer 26

Light from the light source travels through the condenser lens, then through the thin specimen. Then, it travels up the convex objective lens, through to the ocular lens where the image can be viewed.

Question 27

How do fluoroscence microscopes work?

Answer 27

The sample to be viewed is stained with fluoroscent substance. The fluorescent substance will attach to the desired structure. The sample is illuminated with high-intensity light cuasing the fluoroscent substance to emit light. This fluoroscent light is directed through filters that separate it from surrounding light.

The viewer is able to only see the areas of the sample that are fluorescing.

Question 28

Define fluoroscence.

Answer 28

Fluorescence is the ability of certain chemicals to give off visible light after absorbing radiation which is not normally visible.