Topic 1:Cell structure

Question 1

A common method of examining material with light microscope is

Answer 1

To cut thin slices of material called section

Question 2

The advantage of cutting sections

Answer 2

Thin enough to allow light to pass through

Question 3

Light passing through the sections produces an image which can then be magnified using

Answer 3

Objective lens and eyepiece lens

Question 4

Prepared slide contain material that has been

Answer 4

Killed and preserved in a life like state

Question 5

Temporary slides are ____ and _____ to prepare and are often used to examine ______

Answer 5

Quicker; easier; fresh material containing living cells

Question 6

Sections are typically stained because

Answer 6

Structures in cell are transparent hence difficult to distinguish

Question 7

Sometimes macerated(chopped up) material can be used as when examining

Answer 7

The structure of wood(xylem)

Question 8

Some temporary stains commonly used

Answer 8

Iodine in Pottasium Iodide is useful for plant specimens- will colour starch blue black and nuclei and cell walls pale yellow.
Dilute methylene blue solution used to stain animal cells such as cheek cells.

Question 9

Procedure of making temporary slides(2 steps)

Answer 9

1.Place the biological specimen on a clean glass slide and add one or two drops of stains.
2.Carefully lower a cover over the specimen.

Question 10

Advantages of placing a coverslip on the specimen

Answer 10

Protects the microscope lens and prevents the specimen from drying out.

Question 11

How to prevent drying out of a specimen

Answer 11

Adding a drop of glycerine and mixing it with the stain.

Question 12

Suitable animal material

Answer 12

Human cheek cells obtained by gently scraping the lining of the cheek with a finger nail.

Question 13

Suitable plant material

Answer 13

Onion epidermal cells, lettuce epidermal cells, chlorella cells, Moss slip leaves

Question 14

Define Magnification

Answer 14

Is the number of times larger an image of an object is than the real size of the object.

Question 15

Magnification formula

Answer 15

Magnification= observed size of the image/actual size

Question 16

Micrographs

Answer 16

A picture taken with the aid of a microscope

Question 17

Define eyepiece graticule

Answer 17

Small scale that is placed in a microscope eyepiece

Question 18

The eyepiece graticule is placed in the microscope eyepiece so that

Answer 18

It can be seen at the same time as the iobject to be measured

Question 19

The eyepiece graticule can be calibrated using

Answer 19

Stage micrometer

Question 20

Define stage micrometer

Answer 20

Very small, accurately drawn scale of known dimensions, engraved on a microscope slide

Question 21

mm to micrometer

Answer 21

x10^-3

Question 22

micrometer to nanometer

Answer 22

x10^-3

Question 23

mm to nm

Answer 23

x10^-6

Question 24

Define resolution

Answer 24

The ability to distinguish between the objects very close together

Question 25

The higher the resolution the greater

Answer 25

The detail that can be seen

Question 26

The maximum resolution of a light microscope is

Answer 26

200nm

Question 27

A resolution of 200nm means that

Answer 27

If two points or object are closer than 200nm, they cannot be distinguished as separate

Question 28

The longer the waves

Answer 28

The lower the frequency

Question 29

Wavelength changes with energy

Answer 29

The greater the energy, the shorter the wavelength

Question 30

Why is a mitochondrion seen using a light microscope but not ribosomes

Answer 30

Because the mitochondrion is large enough to interfere with the light waves, however the ribosomes are far too small to have any effect on the light waves

Question 31

The limit of resolution is

Answer 31

Half the wavelength of the radiation used to view it

Question 32

When metals becomes very hot

Answer 32

Some of its electrons gain so much energy that they escape from their orbits.

Question 33

Free electrons behave like

Answer 33

electromagnetic radiation

Question 34

Electrons are suitable for microscopy for two reasons

Answer 34

1.They have extremely short wavelengths(as short as X-rays 2.They are negatively charged so they can be focused using electromagnets

Question 35

A magnet can be made to alter the path if a beam

Answer 35

The equivalent of glass lens bending light

Question 36

How does Transmission electron microscope work

Answer 36

1.The beam of electrons is passed through the specimen before being viewed. 2.Only the electrons that are transmitted are seen. 3.This allows us to see thin sections of specimen and thus see inside the cells.

Question 37

How does a scanning electron microscope work

Answer 37

The electron beam is used to scan surface of the structures and only the reflected beam is observed.

Question 38

The advantage of SEM

Answer 38

Surface structure can be seen

Question 39

How is a 3d appearance achieved in SEM

Answer 39

It is because much of the specimen is in focus at the same time

Question 40

Disadvantage of SEM

Answer 40

It cannot achieve the same resolution as TEM

Question 41

Resolution of SEM

Answer 41

3nm to 20nm

Question 42

It is not possible to see electron beams. How is this problem resolved

Answer 42

To make the image visible the electron beam is projected on a fluorescent screen. The areas hit by electron shine brightly giving an overall black and white image

Question 43

The stains used in electron microscopy contain

Answer 43

Heavy metal atoms which stop the passage of electrons. The more densely stained