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BIOLOGY A-LEVEL > CELLS 1 (fractionation, microscopes & viruses) > Flashcards

CELLS 1 (fractionation, microscopes & viruses) Flashcards

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1
Q

what is the resolution of an optical microscope (light)?

A

200nm

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2
Q

what is the resolution of a SEM microscope?

A

20nm

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3
Q

what is the resolution of a TEM microscope?

A

0.1nm

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4
Q

which type of microscope forms coloured images?

A

Light only. NOT ANY ELECTRON

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5
Q

which microscope type produces 3D images?

A

SEM

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6
Q

what is the difference in electron beam firing in the two types of electron microscope?

A

SEM: electron beam fired and bounce off of sample, then focus on a fluorescent screen

TEM: electron beams fired through sample

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7
Q

Which microscope has biggest resolution and magnification?

A

transmission electron microscope

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8
Q

equation for magnification

A

mag = image/actual
I
A M

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9
Q

what’s some drawbacks of an electron microscope?

A

B+W image only, expensive, need training to use, samples in vacuum ( electrons absorbed by air)

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10
Q

why is electron microscope sample in a vacuum?

A

Electrons are absorbed by the air, so the beam wouldn’t reach the specimen.

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11
Q

what is the relationship between wavelength and resolution?

A

inversely proportional.
increase wavelength = down res.

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12
Q

why is the resolution higher in a TEM microscope than light microscope?

A

light has a longer wavelength than electrons.

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13
Q

how to convert between micrometers (μm) and nanometres (nm)

A

μm -> nm
= x1000

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14
Q

mm -> μm conversion

A

x1000

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15
Q

define resolution

A

the ability to distinguish between 2 points on an image

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16
Q

what is the order of units. biggest to smallest?

A

cm -> mm -> μm -> nm

17
Q

define magnification

A

how much bigger a sample appears to be under a microscope than it is irl.

18
Q

positives of a light microscope over electron.

A

portable, cheap, easy to use, live samples, colour image

19
Q

define cell fractionation

A

separating cell organelles out by breaking them up to produce a pure sample of one organelle

20
Q

order of density of organelles

A

nucleus, chloroplast, mitochondria, lysosomes, rough er, plasma membrane, smooth er, ribosomes

21
Q

which organelle is separated last into the pellet in cell fractionation?

A

ribosomes

22
Q

which organelle is separated first into the pellet in cell fractionation?

A

nucleus

23
Q

what are organelles separated by in cell fractionation?

A

order of density. biggest to smallest.

24
Q

what is meant by homogenisation in cell fractionation?

A

when the cells are broken open in a blender or homogeniser

25
Q

what are samples spun in during cell fractionation?

A

centrifuge

26
Q

what is the liquid that rises in cell fractionation called?

A

The supernatant, re-spunfaster each time until only pellet remains.

27
Q

why do you put the tissues into ice cold mixture in in cell fractionation?

A

To reduce enzyme activity to prevent digestion of organelles

28
Q

why do you put the tissues into isotonic mixture in cell fractionation?

A

it has the same water potential as the tissue to prevent osmotic damage eg shrinking due to pressure changes

29
Q

why do you put the tissues into buffer solution in cell fractionation?

A

so the pH is constant to avoid protein denaturation

30
Q

what is the role of cell fractionation

A

to study a particular organelles function and structure

31
Q

what type of cell is a virus?

A

its acellular because it does not have a cellular structure

32
Q

what’s a virus made of?

A

nucleic acids surrounded by capsid proteins

33
Q

what’s a viruses capsid?

A

The protein coat around the nucleic acid virus core

34
Q

how do viruses replicate?

A
  • attachment proteins to bind to complementary receptor proteins on a host cell surface
  • inject dna to host cells
  • host cell replicates
35
Q

what’s the role of attachment proteins on a virus?

A
  • to bind to host cells in order to replicate.
36
Q

what enzyme do viruses use to insert its RNA into host cells dna

A

reverse transcriptase enzymes

BIOLOGY A-LEVEL (8 decks)

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