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Biology Cells > Cell structure and microscopy > Flashcards

Cell structure and microscopy Flashcards

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1
Q

What do microscopes do?

A

Produce a magnified image of an object

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2
Q

What lenses are used in pairs in a compound light microscope by acting as a magnifying glass?

A

Convex glass lens

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3
Q

Why can light microscopes only distinguish between two objects if they are 0.2um (or further) apart?

A

Light rays have a relatively long wavelength

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4
Q

What can overcome the limitation of light rays’ wavelength?

A

Using beams of electrons rather than beams of light

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5
Q

How do the shorter wavelength beams of electron’s affect the microscope?

A

The microscope can distinguish between two objects only 0.1nm apart

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6
Q

What are the two main microscopes?

A

1) Light microscope
2) Electron microscope

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7
Q

What is the material that is put under the microscope called when
a) it is out of the microscope?
b) it is under the microscope?

A

a) the object
b) the image

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8
Q

What is magnification?

A

How many times bigger the image is compared to the object

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9
Q

What is the formula for calculating magnification?

A

M = Image size / actual size

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10
Q

How many nm make up a um?

A

1000

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11
Q

What is the resolution of a microscope?

A

The minimum distance apart that two objects can be in order for them to appear as separate items

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12
Q

Does a microscope using a longer wavelength (E.G. light microscope ) have a higher or lower resolution?

A

Lower resolution

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13
Q

Why do scientists isolate organelles?

A

To study the function and structure of the orgnanelles that make up cells

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14
Q

Why does an image that has increasing magnification appear more blurry?

A

Resolution is not increasing so magnification can no longer reveal any more detail

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15
Q

What is cell fractionation?

A

The process where cells are broken up and the different organelles they contain are separated out.

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16
Q

What 3 properties are supposed to be in the fractionating solution?

A

1) Cold
2) Buffered
3) same water potential as the tissue

17
Q

Why must a fractionating solution be cold?

A

To reduce enzyme activity that might break down organelles

18
Q

Why must the fractionating solution be the same water potential of the tissue - isotonic?

A

to prevent organelles bursting or shrinking as a result of osmotic gain or loss of water.

19
Q

Why must the fractionating solution be buffered ?

A

So the pH does not fluctuate which could alter the structure of the organelles or affect the functioning of the enzymes

20
Q

What are the 2 steps fractionation?

A

1) Homogenation
2) Ultracentrifugation

21
Q

What is homogenation?

A

The breaking up of cells which releases the organelles into a homogenate fluid.

22
Q

What do you do to the homogenate before ultracentrifugation?

A

It is filtered to remove any complete cells and large pieces of debris

23
Q

What is ultracentrifugation?

A

The process by which fragments in the filtered homogenate are separated in a centrifuge

24
Q

What does a centrifuge do?

A

Spins tubes at a very high speed to create a centrifugal force

25
Q

What organelle is heaviest so separates into the pellet first at the lowest speeds?

A

the nucleus

26
Q

What is the fluid at the top of the pellet called?

A

Supernatant

27
Q

What happens to the supernatant?

A

It is transferred to another tube and is spun in the centrifuge at a faster speed than before

28
Q

What organelle is separated second?

A

The Mitochondria

29
Q

What organelle is separated third from the supernatant?

A

Lysosomes

30
Q

Why does an electron microscope have a higher resolution?

A

The electron beam has a very short wavelength

31
Q

Why can the charged electrons beam be focused using electromagnets?

A

Electrons are negatively charged.

32
Q

Why does a near-vacuum have to be created within the chamber of an electron microscope for it to work effectively?

A

The electrons are absorbed or deflected by the molecules in the air.

33
Q

What are the two types of electron microscope?

A

1) Transmission electron microscope (TEM)
2) Scanning electron microscope (SEM)

34
Q

What does a TEM consist of?

A

An electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet

35
Q

Why do some bits of the specimen appear dark or bright on the TEM?

A

The parts that absorb the electrons appear bright and the parts that allow electrons to pass through appear bright

36
Q

What can the image produced on screen by the TEM and called?

A

A photomicrograph

37
Q

What are two reasons why the resolving power of a TEM can’t always be achieved?

A

1) difficulties preparing the specimen
2) a high energy electron beam is required and this may destroy the soecimen

Biology Cells (4 decks)

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