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Biology-topic 2 cells > Microscopy > Flashcards

Microscopy Flashcards

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1
Q

What is the equation for maginification?

A

i = am

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2
Q

How do you convert mm to micrometers?

A

x1000

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3
Q

What is magnification?

A

the increase in the apparent size of an object

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4
Q

What is resolution?

A

the ability to distinguish between two points as separate

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5
Q

Why are light microscopes limited?

A

the wavelength of light is too long

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6
Q

What does TEM stand for?

A

transmission electron microscope

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7
Q

What does SEM stand for?

A

scanning electron microscope

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8
Q

How are the lenses focused in TEM and SEM microscopes?

A

with electromagnetic lenses

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9
Q

What is the maximum magnification of a light microscope?

A

x1500

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10
Q

What is the maximum magnification of a TEM/SEM microscope?

A

up to x500,000

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11
Q

What is the resolving power of a light microscope?

A

200nm

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12
Q

What is the resolving power of TEM microscopes?

A

1nm

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13
Q

What is the resolving power of a SEM microscope?

A

20nm

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14
Q

Name the status of the sample in all 3 microscopes

A

living or dead in light/ dead in TEM and SEM

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15
Q

Which one of the microscopes does the specimen have to be extremely thin for?

A

TEM

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16
Q

Which microscopes are more expensive?

A

TEM and SEM

17
Q

Which one is a 3d image?

A

SEM

18
Q

What colour is the image of the microscopes?

A

coloured - light/ black and white - TEM and SEM

19
Q

Why does TEM and SEM have to be in a vacuum?

A

As they use electrons to illuminate the specimen, the electrons would hit air particles

20
Q

Why does the sample have the be extremely thin?

A

To allow the electrons to penetrate the sample

21
Q

What are the limitations of electron microscopes?

A

vacuum has to be used to prevent scattering of electrons so the sample has to be dead/ complex preparation and staining of specimens are required/ image only in black and white/ the image may contain artefacts such as distortion of key features if specimen was dehydrated

22
Q

What is an eyepiece graticule?

A

a small piece of glass with a measurement scale that fits inside a microscope

23
Q

Say what is special about the scale of an eyepiece graticule

A

the scale remains constant no matter the magnification

24
Q

What is used to calibrate the eyepiece graticule?

A

a special microscope slide called a stage micrometer

25
Q

What is calibration?

A

involves fixing known points and constructing a scale between them

26
Q

What is cell fractionation/ differential centrifugation?

A

the process of cells being broken up to allow the different organelles that they contain to be separated

27
Q

Explain how to use an eyepiece graticule to calculate the size of a structure

A

place the micrometer on the stage and line up the scales on the graticule and micrometer, count how many graticule divisions are in 100micrometers of the micrometer - length of 1 eyepiece division = 100micrometers/no of divisions, use values to calc the size

28
Q

What is the first step to differential centrifugation?

A

chop up fresh tissue in an ice cold, isotonic buffer solution

29
Q

Name and explain the conditions of the solution used in step 1 of d.c

A

ice cold - slows down enzyme activity / isotonic - water potential stays equal to tissue so that organelles won’t shrink or burst as a result of osmotic water loss/gain / buffered - so the pH doesn’t fluctuate which could alter the structure of organelles or affect the functioning of enzymes

30
Q

What is the second step to differential centrifugation?

A

put the chopped up tissue into a blender/homogeniser which breaks open the cells

31
Q

What is the third step to differential centrifugation?

A

filter the mixture to remove the debris/homogenate

32
Q

What is the fourth step to differential centrifugation?

A

pour the mixture into a centrifuge with tubes and spin very quickly, the denser parts get separated to the bottom of the tube where they form a pellet called sediment

33
Q

What is within the sediment?

A

the nuclei

34
Q

What is the fifth step to differential centrifugation?

A

the liquid layer on the top (called the supernatant) is poured into a fresh tube leaving the sediment behind

35
Q

What is the sixth step to differential centrifugation?

A

the supernatant is spun again for longer and at a faster speed to produce another sediment containing mitochondria and chloroplasts

36
Q

What are the lightest organelles separated by differential centrifugation?

A

ribosomes

Biology-topic 2 cells (9 decks)

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