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Biology > 3.2 Cells - structure, methods to study cells > Flashcards

3.2 Cells - structure, methods to study cells Flashcards

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1
Q

what are differences between eukaryotes and prokaryotes?

A

eukaryotes are larger

eukaryotes have a true nucleus, prokaryotes don’t

eukaryotes have membrane bound organelle

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2
Q

cell surface membrane structure

A

found in all cells

phospholipid bilayer - molecules embedded within and attached on the outside (proteins, carbohydrates and cholesterol)

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3
Q

cell surface membrane function

A

controls the entrance and exit of molecules

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4
Q

nucleus structure

A

nuclear envelope - double membrane

nuclear pores

nucleoplasm - granular, jelly like material

chromosomes - protein bound, linear DNA

nucleolus - smaller sphere in the nucleoplasm which is the site of rRNA production and ribosome synthesis

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5
Q

nucleus function

A

site of DNA replication and transcription

contains the genetic code for each cell

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6
Q

mitochondria structure

A

double membrane

an inner membrane called the cristae

the fluid center called the mitochondrial matrix

contains 70S ribosomes and circular DNA

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7
Q

mitochondria function

A

site of aerobic respiration and ATP production

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8
Q

chloroplast function

A

site of photosynthesis

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9
Q

chloroplast structure

A

surrounded by a double membrane

contains thylakoids (folded membranes embedded with pigment)

the fluid filled stroma contains enzymes for photosynthesis

found in plants

contains 70s ribosomes and circular DNA

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10
Q

golgi apparatus and vesicles structure

A

folded membranes making cisternae

secretory vesicles pinch off from the cisternae

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11
Q

golgi apparatus and vesicles function

A

transport, modify and store proteins and lipids produced by the RER and SER

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12
Q

lysosomes structure

A

bags of digestive enzymes - can contain 50 different enzymes

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13
Q

lysosomes function

A

hydrolyse pathogens in phagosomes

completely break down dead cells

exocytosis - release enzymes outside the cell to destroy material

digest worn out organelles for reuse of materials

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14
Q

ribosome structure

A

small granules made up of two sub units of proteins and rRNA

80S - large ribosome found in eukaryotic cells

70S - smaller ribosomes found in prokaryotic cells, mitochondria and chloroplasts

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15
Q

ribosome function

A

the site of protein synthesis

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16
Q

RER function

A

protein synthesis

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17
Q

RER structure

A

have folded membranes called cisternae

have ribosomes on the cisternae

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18
Q

SER function

A

synthesises and stores lipids and carbohydrates

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19
Q

SER structure

A

have folded membranes called cisternae

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20
Q

cell wall structure

A

in plants and fungal cells

plants - made of microfibrils of the cellulose polymer

fungi - made of chitin

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21
Q

cell wall function

A

provides structural strength to the cell

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22
Q

vacuole structure

A

filled with fluid surrounded by a single membrane called a tonoplast

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23
Q

vacuole function

A

makes cells turgid and therefore provides support

temporary store of sugars and amino acids

the pigments are responsible for coloured petals which attract pollinators

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24
Q

what does a capsule do?

A

provides protection from other cells and helps bacteria stick together

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25
Q

what are the 3 main adaptations of specialised cells?

A

large surface area

high number of mitochondria

lots of RER and golgi

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26
Q

what are the key differences between prokaryotic and eukaryotic cells?

A

the cells are much smaller

no membrane bound organelles i.e. mitochondria

smaller ribosomes - 70S

a cell wall made of murein - unlike plant cell wall made of cellulose

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27
Q

what type of ribosomes do bacterial cells contain?

A

smaller ribosomes that are 70S rather than 80S

28
Q

what are prokaryotic cell walls made from?

A

do not contain cellulose or chitin

made of a glycoprotein called murein

29
Q

what are the three additional features that bacteria can also contain?

A

plasmids - rings of DNA containing genes linked to survival such as antibiotic resistance

capsule - provides protection from other cells and helps bacteria agglutinate (stick together)

flagella - used for locomotion

30
Q

what type of microscope is an optical microscope?

A

light microscope

31
Q

what type of microscope is a scanning or transmission microscope?

A

electron microscope

32
Q

how is an image created in a light microscope?

A

a beam of light is condensed to form an image

33
Q

what type of lens is used to condense the beam of light in a light microscope?

A

a glass lens

34
Q

why does a light microscope have a poorer resolution?

A

due to having a longer wavelength

35
Q

can light microscopes view living samples?

A

yes

36
Q

does a light microscope have a lover magnification than an electron microscope?

A

yes

37
Q

what colour images are produced from a light microscope?

A

coloured not black and white

38
Q

how is an image created in an electron microscope?

A

a beam of electrons is condensed to create the image

39
Q

what is used to condense the beam in an electron microscope?

A

electromagnets

40
Q

why does an electron microscope have a higher resolving power?

A

they have a shorter wavelength

41
Q

does an electron microscope have a higher magnification then a light microscope?

A

yes

42
Q

what colour images do electron microscopes produce?

A

black and white

43
Q

what does the sample have to be like in an electron microscope?

A

must be in a vacuum and therefore non-living

44
Q

why do light microscopes have poor resolution?

A

due to the long wavelength of light

45
Q

what are not visible in a light microscope?

A

small organelle

46
Q

why must samples be in a vacuum in an electron microscope?

A

the electrons are absorbed by air

47
Q

what is the equation for magnification?

A

image divided by the actual

48
Q

what should you always measure the image size in when calculating magnification?

A

millimeters

49
Q

how do you convert from millimeter to micrometer (um)?

A

times by 1000

50
Q

how do you convert from micrometer (um) to nanometer (nm)?

A

times by 1000

51
Q

what can the eyepiece graticule be used to measure?

A

to measure the size of objects you are viewing under the microscope.

52
Q

what do you have to do with the eyepiece every time you change the objective lens?

A

calibrate the eyepiece to work out what the distance is between each division at that magnification.

53
Q

what is used to calibrate the eyepiece graticule?

A

A stage micrometer

54
Q

what is stage micrometer?

A

This is a glass slide with a scale on it which you place on the stage.

The scale on the stage micrometer is typically 2mm long and
the sub-divisions are 10µm apart

55
Q

what are the steps for studying cells using calibration?

A

Step 1 - Line up the stage micrometer and eyepiece graticule whilst looking through the eyepiece.

Step 2 – Count how many divisions on the eyepiece graticule fit into one division on the micrometer scale.

Step 3 – Each division on the micrometer is 10µm, so this can be used to calculate what one division on the eyepiece graticule is at that current magnification

56
Q

what are cell fractionation and ultracentrifugation used to break down?

A

Cell fractionation and ultracentrifugation are used to break down
cells and remove organelles so that they can be studied.

57
Q

how are cells separated in cell fractionation?

A

is done using a homogeniser (blender)

58
Q

what must the solution be during homogenisation?

A

cold

isotonic

buffered

59
Q

why must the solution be cold during homogenisation?

A

cells must be kept in a solution that is cold to reduce enzyme activity to prevent the breakdown of cell components.

60
Q

why must the solution be isotonic during homogenisation?

A

to prevent any movement of water by osmosis which could result in organelles shrivelling or bursting.

61
Q

why must the solution be buffered during homogenisation?

A

to resist pH changes

this is to prevent damage to organelles and enzymes.

62
Q

why must the solution be filtered after being broken up?

A

Once the cell has been broken open the solution must be filtered to remove larger pieces of debris.

63
Q

what is the homogenate solution ready for after being filtered?

A

ready to be centrifuged

the solution is placed into a centrifuge which spins at high speed to separate organelles depending on their density due to the centrifugal force

64
Q

what does the supernatant contain after one spin?

A

supernatant after the first spin at low speed- pellet
contains the nuclei

65
Q

what does the supernatant contain after the second spin?

A

supernatant after the second spin at medium speed pellet contains mitochondria and chloroplasts (if a plant cell)

66
Q

what does the supernatant contain after the third spin?

A

supernatant after the third spin at high speed- pellet
contains lysosomes and SER/RER.

67
Q

what does the supernatant contain after the fourth spin?

A

supernatant after the fourth spin at very high speed- the
pellet contains ribosomes

Biology (7 decks)

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