Analysis Of Cells Flashcards

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1
Q

What is the equation for magnification?

A

Size of image
________________

Size of real object

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2
Q

How many micrometers are in a mm?

A

1000

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3
Q

What are the two types of microscope?

A

Optical (light) and electron

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4
Q

What is the magnification of an optical microscope?

A

X1500

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5
Q

What is the magnification of an electron microscope?

A

X1500000

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6
Q

How do TEMs work?

A

Use electromagnets to focus a beam of electrons on a specimen (darker parts - more dense, more electrons absorbed)

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7
Q

Give an advantage and disadvantage of a TEM

A

High resolution

Thin specimens only

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8
Q

How do SEMs work?

A

Scan a beam of electrons across the specimen and knock off electrons, electrons gathered in cathode ray tube to form image

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9
Q

Give an advantage and disadvantage of TEMs

A

Thick specimens
3D
Lower resolution than SEM

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10
Q

How do you prepare a temporary mount?

A

Drop of water on slide
Tweezer thin section
Drop of stain e.g. Iodine in potassium iodide
Cover slip using mounted needle

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11
Q

What are the 3 phases of cell fractionation?

A

Homogenisation
Filtration
Ultracentrifugation

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12
Q

Describe the homogenisation of cells

A

Cells are vibrated or ground up
Breaks up plasma membrane and releases organelles
Ice cold, isotonic, pH

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13
Q

In homogenisation, why should the solution contain a buffer, be isotonic and ice cold?

A

Maintain pH
Prevent osmosis damaging organelles
Stop enzymes working/breaking down organelles

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14
Q

Describe the process of filtration

A

Homogenised cell solution passes through gauze to separate large cell debris

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15
Q

Describe ultracentrifugation

A

Cell in tube spun in centrifuge at low speed
Heaviest organelles form thick sediment at bottom (pellet)
Other organelles stay suspended (supernatant)
Supernatant drained off
Repeat

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16
Q

What are the heaviest and lightest organelles?

A

Nucleus and ribosome

17
Q

What is meant by magnification?

A

How much bigger the image is than the specimen

18
Q

What is meant by resolution?

A

How detailed the image is

How well a microscope can distinguish two points that are close together

19
Q

What are artefacts?

A

Something you see down a microscope that isn’t part of the specimen e.g. Air bubble, dust

20
Q

What is needed to measure size of object under microscope?

A

Graticule

Stage micrometer