Lesson 1 Microscopy

Question 1

What is immersion

Answer 1

Placing under a liquid

Question 2

Describe resolution

Answer 2

How clear/ focused an image is

The ability to distinguish between two objects

Question 3

When was the first compound microscopes developed

Answer 3

They were developed in the latee 16th and early 17 centuries

Question 4

1833 what did Robert brown first to do?

Answer 4

First to descibe the nucleus of a plant

Question 5

1860 what did luis Pasteur do

Answer 5

He disposed the theory of spontaneous generation of cells by demonstrating that bacteria would only grown in sterile nutrient broth after it has been exposed to air

Question 6

Outline the importance of microscopes in the study of living organisms

Answer 6

Allow us to see organelles inside cells

Question 7

Suggest with reasons, why cell theory was not fully developed before the mid 19th century

Question 8

Dry mount slide preparation

Answer 8

Solid specimens and viewed whole or cut into very thin slices called sectioning. The specimen is placed in the center of the slide and a cover slip is placed over the sample

Ie. Hair,pollen dust, insect parts, muscle tissue, plants

Question 9

Wet mount slide preparations

Answer 9

Specimens are suspended in a liquid such as water or an immersion oil. A cover slip is then placed on from an angle

I.e aquatic samples or other living organisms

Question 10

Squash slide specimen preparation

Answer 10

A wet mount is first prepared, then a lense tissue is used to gently press down the cover slip

I.e soft samples (root tip squashes are used to look at cell division)

Question 11

Smear slides specimen preparation

Answer 11

The edge of a slide is udsed to smear the sample creating a thin, even coating on another slide,a cover slip is then placed over the sample

I.e blood

Question 12

Why do we section and stain cells?

Answer 12

Biological material is not coloured so is difficult to see details
Can be difficult to section.

Question 13

How does staining work?

Answer 13

It increases the contrast as you are looking at sample as different components within a cell take up stains to different degrees.

Question 14

Example of postively charged dyes

Answer 14

Crystal violet or methylene blue

Question 15

How do positively charged dyes work

Answer 15

They are attracted to negatively charged materials in the cytoplasm leading to staining of cell components

Question 16

Examples of negatively charged dyes

Answer 16

Nigrosin
Congo red

Question 17

How do negatively charged dyes work

Answer 17

Negatively charged dyes are repelled by the negatively charged cytosol. They stay outside leaving cells unstained against the stained background.

Question 18

Two uses of differential staining

Answer 18

Used to distinguish between different organisms that would otherwise be difficult to identify

It can also be used to differentiate between different organism within a tissue sample