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MPW biology > 2.1.1 - Cell structure > Flashcards

2.1.1 - Cell structure Flashcards

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1
Q

What is cell theory

A

The theory that all living organisms are made up of one or more cells and that cells only arise via the division of pre-existing cells.

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2
Q

What does microscopy allow?

A

the ability to observer and investigate the many different cells types and the various different cell structures.

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3
Q

What is an artefact

A

Structures visible on an image that having been formed during the sample preparation, which aren’t actually present in the cell, ie are bubbles or mesosomes

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4
Q

light microscope energy source

A

Visible light

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5
Q

how does a light microscope work

A

lenses made of glass bend light that has passed through the specimen such that you see a magnified image

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6
Q

thickness of light microscope specimens

A

thin/flat

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7
Q

why must light microscopes have thin/flat specimens

A

so the light can pass through the specimen into you eyes

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8
Q

advantages of light microscope (6)

A

we can see true colours
living processes can be seen
inexpensive to buy and maintain
easy sample preparation
sample preparation less likely to cause artefacts
straightforward

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9
Q

why are stains used (2)

A

cell = colourless, so the stains make specific parts visible
contrast

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10
Q

how to calculate overall magnification of light microscope

A

magnification of eyepiece lens x magnification of objective lens

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11
Q

light microscope magnification

A

x1500

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12
Q

light microscope resolution

A

200nm

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13
Q

laser scanning confocal microscope energy source

A

ultraviolet light

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14
Q

why does an LSCM have a higher resolution that light microscope

A

ultraviolet light has a shorter wave length than visible light.

shorter wave length = higher resolution

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15
Q

how to prepare specimen for LSCM

A

cell treated with antibodies which bind to specific proteins
the antibodies have floutesecnt dyes attaches, which absorbs light from the laser and re-emits the light of a specific wavelength

or

cells can be genetically modified to produce fluorescent proteins which reveal their own location.

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16
Q

LSCM, how does it work

A

laser scans across the specimen in a fixed plain, illumination only a single point at a time
high resolution, but 2D ‘slice’
many slices can be put into a computer programme to create a 3D image.

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17
Q

LSCM advantages

A

it can show the precise location of one or more specific types of protein at different depths within a cell.
if the cell in prepared appropriately, living cells can be viewed, and changed over time can be tracked, such as the position and length of spindle fibres during cell division.

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18
Q

TEM and SEM energy source

A

beam of electrons, which is then picked by electromagnetic which are used as lenses

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19
Q

how does a TEM work/ preparation

A

thin section of cell is stained with a heavy metal such as gold. the electron beam passes through the specimen and onto a detector, but the are where the heavy metals atom are the electrons can’t pass through and are blocked, providing contrast to the image

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20
Q

TEM image description

A

Flat, but extremely detailed due to high resolution, artificially coloured, 2D

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21
Q

TEM magnification

A

x500000

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22
Q

TEM resolution

A

0.5 nm

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23
Q

how does a SEM work/ preparation

A

thin section of cell is stained with a heavy metal such as gold. the electron beam is directed across the surface specimen, and where the heavy metal is the electrons are reflected of the surface of the cell and create an image on the detector

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24
Q

SEM image description

A

Surface view of a cell where the image has a 3D appearance

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25
Q

SEM magnification

A

x100000

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26
Q

SEM resolution

A

5nm

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27
Q

advantages of electron microscopes

A

very high resolution and magnification

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28
Q

disadvantages of electron microscopes

A

black and white image produces, however artifical colours can be added using a computer, and the components must be digitally enhanced for non-experts to interpret the image
sample preparation is technically demanding
much training and practice is needed
very large and not portable
very expensive to buy and maintain
vacuum must be maintained so the electron beam isn’t scattered by gas particles, meaning the cell is dead
the sample preparation is generally more likely to form artefacts than light microscopes

29
Q

disadvantages of light microscopes

A

low resolution and magnification

30
Q

what do you call the outer most membrane?

A

plasma membrane or cell surface membrane

31
Q

what are the three types of slide preparations for light microscopy, and which is the most effective

A
  1. Smear
  2. Squash
  3. Sectioning (most effective)
32
Q

Describe smear preparation

A

spreading the sample evenly across a microscope slide, so it forms a thin layer, (so light can pass through)
add colour stain if needed
add coverslip on top of the specimen

33
Q

advantages of smear preparation

A

Living cell can be viewed

34
Q

Describe squash preparation

A

tissue is placed onto a slide
add stain if needed
place coverslip of specimen and gently press down gently to spread out / squash the sample into a thin layer

35
Q

advantages of squash preparation

A

living cells can be viewed

36
Q

describe sectioning preparation

A

tissue is first fixed and preserved using formaldehyde
embedded in solid wax or resin
very thinly sliced with a device called a microtome
place onto a slide and stain if needed
place coverslip over the specimen

37
Q

disadvantages of sectioning preparation

A

living cells CANNOT be viewed

38
Q

example of smear preparation

A

blood

39
Q

example of squash preparation

A

root tip in which is undergoing mitosis

40
Q

Why do we use stains

A

enables cells or cell components to become visible which were previously invisible .

provides contrast between structures so different component or cell types can be distinguished from one another

enable identification of cell types, organelles or specific biological molecules

41
Q

give an example of a stain used in light microscopy

A

methylene blue - Binds to DNA, so nucleus looks blue

42
Q

give an example of a heavy metal used in electron microscope

A

Gold

43
Q

1mm is how many micrometers

A

1000um

44
Q

1mm is how many nano meters

A

1000000nm

45
Q

1um is how many nano meters

A

1000 nm

46
Q

Magnification definition

A

The number of times larger the size of an image is compared to the real object

47
Q

what is the magnification triangle

A
48
Q

Resolution defintion

A

The ability to distinguish two close points as sepatate objects

49
Q

why is it not worthwhile to magnify above x1500 with a light microscope

A

The resolution of the LM is not high enough to make it useful to magnify above x1500; no further detail would be seen in the image. The resolution of the LM is 200nm, limited by the long wavelength of light

50
Q

ultrastrucutre definition

A

fine details of cell structure

51
Q

organelle definition

A

a cell component with a specific structure and function

52
Q

eukaryote cell

A

A cell with a nucleus and other membrane bound organelles.

53
Q

eukaryote cell size

A

10-100um

54
Q

prokaryote definition

A

cells without a membrane bound nucleus or organelles.

55
Q

prokaryote size

A

1-2um

56
Q

cell wall materials

A

prokaryotes - peptidoglycan

fungi - chitin

plant- cellulose

protocists - cellulose cell wall

57
Q

how would you describe the shape of endoplasmic reticulum

and what is the funciton of each type

A

membrane bound flatted tubes called cisterna with an internal space called the lumin containing specific proteins.

rer - proteins synthesis

ser - lipid synthesis

58
Q

how would you describe the shape of the golgi, and what is its function

A

membrane bound flatted discs called cisternae with a lumin containg specialsed ezumes.

role - modify proteins and packaging into secratory vesicles

creates lysosomes.

59
Q

lysosomes shape and function

A

spherical membrane-bound organelle containing hydrolytic enzymes such as protease.

digest old/faulty organelles

digestion of engulfed pathogens

THE MEMBRANE IS IMPORTANT BECAUSE IT ENSURE THAT THE HYDROLYTIC ENZYMES DO NOT LEAK OUT AND CASUE DAMGE TO THE CELL.

60
Q

mitochondria shape and function

A
61
Q

chloroplast design and function

A

double membrane structure

fluid within is called the stroma, contains many enzymes needed in photosynthesis

thylakoid membranes contain chlorophlyll

msny thylakoid are in a blob shape called the granum

62
Q

vacuole function

A

membrane enclosed compartment

storage role

maintains cell turgor - water moves into the vacuole via osmosis, increases vacuole volume, prssure exerted against cell wall which cant expand therfore cell becomes turgid

63
Q

centrioles design and function

A

short cylinder-shaped strucutre at a right angle to each other

made of microtubles

only in animal cells

64
Q

flagella

A

cell movement

9 +2 arrangement of microtubles

an extenision of the plasma membrnae

65
Q

cytoskeleton deffinition

A

a network of protein strands found in the cytoplasm of te cytoskeleton

66
Q

microtubles

A

made of tubulin

  • transport vesicle and organelle movements
  • movement of chlorplast

centrioles - organise spindle fibres during cell division

  • cell movement via a flagella
67
Q

microfillaments

A

very fine threads of actin

give the cell mechanical strength and determines the cell shape

68
Q

nucleolus function

A

production of RNA

MPW biology (26 decks)

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