Chapter 1 ~ Basic Components Of Living Systems

Question 1

What does cell theory state?

Answer 1

Both animal and plant tissue is composed of cells
Cells are the basic unit of all life
Cells only developed from existing cells

Question 2

How many lenses does a compound light microscope have and describe how it works

Answer 2

It has two lenses the objective lens and the eyepiece lens.
The objective lens produces a magnified image. This is magnified again by the eyepiece lens.

Question 3

What are the four types of sample preparation?

Answer 3

1. Dry mount
2. Wet mount.
3. Squash slides
   4.Smear slides

Question 4

Explain dry mount

Answer 4

Solid specimens are viewed, whole or cut into very thin slices with a sharp blade. This is known as sectioning the specimen is placed on the centre of the slide and a cover slip is placed over the sample.

Question 5

Explain, wet mount

Answer 5

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

Question 6

Explain squash slides

Answer 6

A wet mount is first prepared, then a lens tissue is used to gently press down the cover slip, depending on the material potential damage to a cover slip can be avoided by squashing the sample between two microscope slides. This is good technique for soft samples.

Question 7

Explain smear slides.

Answer 7

Edge of a slide is used his near the same, this creates a thin, even coating. A coverslip is then placed over the sample

Question 8

What is differential staining?

Answer 8

Technique involving many chemicals stains being used to stain different parts of cells in different colours

Question 9

What are the four common stains?

Answer 9

l. Crystal violet 2. Methylene blue 3. Nigrosin4. Congo red

Question 10

What are the positively charged stains?

Answer 10

Crystal violet🙈methylene blue
Positively charged, so they are attracted to and stain, negatively charge materials

Question 11

What stains are negatively charged?

Answer 11

Nigrosin and Congo red
Negatively charged, therefore cannot enter the cell as cystol repel them. This creates a stained background and the unstained cell stand out.

Question 12

What are the two stains of gram staining

Answer 12

Crystal, Violet and safranin

Question 13

Explain crystal violet

Answer 13

Crystal Violet is added, then iodine into fix the stain and alcohol is used to wash away any unbound stain. gram-positive bacteria appear blue purple as the stain is retained due to the thicker peptidoglycan cells wall later, absorbing the dye

Question 14

Explain gram negative bacteria

Answer 14

Gram-negative bacteria cannot absorb crystal violet stain as their peptidoglycan cell wall is thin, so they do not retain the stain due to the thinner wall. As a result. Saffron is used as a counter stain which turns them to red.

Question 15

How do you calibrate?

Answer 15

Line up the stage micrometre and the eyepiece graticule whilst looking through the eyepiece
Count how many divisions on the eyepiece graticule fit into one division on the micrometre scale
Each division on the micro meter is 10um so this can be used to calculate what one division on the eyepiece graticule at the current magnification

Question 16

What is resolution?

Answer 16

Minimum distance between two objects in which they can still be viewed as separate

Question 17

What is magnification?

Answer 17

How many times larger the images compared to the object

Question 18

What is the calculation for magnification?

Answer 18

Magnification is equal to the size of image divided by the actual size of the object

Question 19

Explain electron microscopy

Answer 19

A beam of electrons with a wavelength of less than one nanometre is used to illuminate the specimen. More detail of the cell ultra structure can be seen as electrons have much smaller wavelength than in light waves. Therefore it can produce a image with magnification up to 500,000x and still have a clear resolution.

Question 20

What are the two types of electron microscope and explain?

Answer 20

Transmission electrum microscope, which has a beam of electrons transmitted through a specimen and focused to produce an image
Scanning electron microscope, which has a beam of electron sent across the surface of a specimen and roof, and the reflected electrons are collected