Studying Cells

Question 1

What is the purpose of studying cells?

Answer 1

Gain an understanding of structures and organelles within cells

Question 2

What is magnification?

Answer 2

The degree to which an object can be made larger

Question 3

What is resolution?

Answer 3

The resolution is the ability to distinguish between objects that are close together

Question 4

How does a light/optical microscope work?

Answer 4

Specimens are illuminated by light, which is focussed using glass lenses and viewed using the eye or photographic film

Question 5

For a light microscope are the specimens dead or alive?

Answer 5

Both

Question 6

Why do cellular structures need to be stained?

Answer 6

Stained using coloured dyes to make them visible. This is an easy staining process

Question 7

Magnification of a light/optical microscope

Answer 7

Limited to x1500

Question 8

What can be viewed with a light/optical microscope?

Answer 8

Large structure like the nucleus

Question 9

Why is the magnification of a light/optical microscope limited?

Answer 9

By using more lenses it magnifies by a large amount but at these higher magnifications it loses resolution. Limited by the wavelength of light, it has a longer wavelength

Question 10

What is the resolution of a light/optical microscope?

Answer 10

200nm (lower)

Question 11

Another positive of a light/optical microscope

Answer 11

It’s cheaper than an electron microscope

Question 12

How does an electron microscope work?

Answer 12

They use a beam of electrons to ‘illuminate’ the specimen. The electrons behave like waves and can easily be produced using a hot wire, focused using electron magnets and detected using a phosphor screen or photographic film. Electrons have shorted wavelengths

Question 13

For an electron microscope can a specimen be dead or alive?

Answer 13

Dead

Question 14

How are electron microscope specimens stained?

Answer 14

Put in a vacuum with no air, stained using heavy metals which is a complex process and can create artefacts (something that shouldn’t be there)

Question 15

What is the magnification of an electron microscope?

Answer 15

x500,000

Question 16

What is the resolution of a electron microscope?

Answer 16

1nm (higher)

Question 17

What can be observed by a transmission electron microscope (TEM)?

Answer 17

Electrons can go through the specimens and enable viewing or internal structures such as organelles. So it’s 2D

Question 18

How are specimens in the transmission electron microscope (TEM)?

Answer 18

Fixed in resin and sliced thin, so must be dead. Electrons are fired through the specimen, thin parts allow more electrons to be transmitted and appear lighter. Whereas thicker parts appear darker because they absorb more electrons

Question 19

What can be observed using a scanning electron microscope (SEM)?

Answer 19

Electrons bounce of the surface or a specimen which always produces a 3D image

Question 20

Why do scanning electron microscopes produce a 3D image?

Answer 20

Specimens are not sliced so electrons bounce of the surface

Question 21

Unit conversions - m to nm

Answer 21

m x 1000 = mm
mm x 1000 = um
um x 1000 = nm

Question 22

Unit conversions - nm to m

Answer 22

nm / 1000 = um
um / 1000 = mm
mm / 1000 = m

Question 23

Unit conversions - m to mm

Answer 23

m x 100 = cm
cm x 10 = m

Question 24

Unit conversions - mm to m

Answer 24

mm / 10 = cm
cm / 100 = m

Question 25

Equation that links Image, actual and magnification

Answer 25

Image —————————— Actual x magnification