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OCR A Level Biology A > 2.1.1 Cell Structure > Flashcards

2.1.1 Cell Structure Flashcards

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1
Q

Define magnification

A

How many times larger an image is than the actual object

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2
Q

Define resolution

A

The degree to which it’s possible to distinguish between two objects that are very close together (higher resolution = greater detail)

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3
Q

What is staining and why is it carried out

A

When you change the colour of a cell so you can see the sub cellular structures more clearly and increases visibility + contrst

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4
Q

What is differential staining

A

When you stain a specimen with multiple dyes, allowing different tissues to show up which creates further contrast

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5
Q

What is sectioning

A

When a specimen is embedded in wax which can then be thinly sliced without distorting the structure of the specimen (useful for soft tissue)

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6
Q

What is fixing

A

Using chemicals to prepare a sample for electron microscopy

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7
Q

How do you figure out magnification (lens)

A

Magnification = eyepiece lens x objective lens

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8
Q

How do you figure out magnification (image)

A

Magnification = image / object

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9
Q

Name as many parts of the ultrastructure of a plant cell

A
  • cytoplasm
  • cell surface/plasma membrane
  • cell wall
  • chloroplast
  • vacuole
  • mitochondrion
  • ribosomes
  • nucleolus
  • nuclear envelope
  • Golgi apparatus
  • smooth endoplasmic reticulum
  • rough endoplasmic reticulum
  • amyloplast containing starch
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10
Q

What is the structure of Nucleus

A
  • surrounded by double membrane called nuclear envelope with pores
  • continuous with endoplasmic reticulum
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11
Q

What is the function of the nucleus

A
  • contains DNA carrying information for protein synthesis
  • chromatin is the genetic material, consisting of DNA wound around histone proteins
  • when cell is about to divide, chromatin coils and condenses to form structures called chromosomes
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12
Q

What is the structure of the nucleolus

A
  • has no membrane around it + contains RNA
  • found inside the nucleus
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13
Q

What is the function of the nucleolus

A
  • makes RNA + ribosomes which pass into the cytoplasm
    > this happens when the outer and inner membranes of the nucleus fuse together allowing dissolved substances to pass through
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14
Q

What is the structure of the RER

A
  • system of membranes containing fluid filled cavities (cisternae) which are continuous with nuclear membrane
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15
Q

What is the function of the SER

A
  • system of membranes containing fluid filled cavities (cisternae) which are continuous with nuclear membrane
  • no ribosomes
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16
Q

What is the structure of the Golgi Apparatus

A
  • stack of membrane-bound flattened sacs (cisternae)
  • secretary vesicles bring materials to + from the Golgi apparatus
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17
Q

What is the function of the Golgi Apparatus

A
  • modifies and packages cell products (proteins)
  • encloses substances in vesicles to be secreted
    > secretory vesicles leave cells + lysosomes stay in the cell
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18
Q

What is the structure of Mitochondria

A
  • 2-5 micro - metres long
  • surrounded by 2 membranes with a fluid filled space
  • inner membrane folded into cristae
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19
Q

What is the function of Mitochondria

A
  • site of aerobic respiration - where ATP is produced
  • lots of mitochondria found in active cells where metabolic activity is higher
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20
Q

What is the structure of Vacuole

A
  • surrounded by membrane called tonoplast (partially permeable) + contains fluid
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21
Q

What is the function of Vacuole

A
  • plant cells have large permanent vacuole
  • filled with water + solutes which maintain cell stability by making cell turgid when it pushes against the cell wall
    > if plant cells are all turgid, it helps support the plant
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22
Q

What is the structure of chloroplasts

A
  • large, 4-10 micro metres
  • surrounded by double membrane / envelope
  • inner membrane has stacks of flattened membrane sacks called thylakoids
    > a stack of thylakoids = a granum
  • fluid filled matrix is called stroma
  • contains loops of DNA and starch grains
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23
Q

What is the function of chloroplasts

A
  • site of photosynthesis
    > 1st stage occurs in grana
    > 2nd stage occurs in stroma
  • chlorophyll molecules found on thylakoid membranes
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24
Q

What is the structure of Lysosomes

A
  • vesicles (bags) formed from golgi apparatus containing digestive enzymes (hydrolytic enzymes) to break down materials
  • surrounded by single membrane
  • abundant in white blood cells that break down microorganisms
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25
Q

What is the function of Lysosomes

A
  • keep the powerful hydrolytic enzymes separate from rest of the cell
  • can engulf old cell organelles + foreign matter
  • responsible for breaking down pathogens ingested by phagocytic cells
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26
Q

What is the structure of Ribosomes

A
  • small spherical organelles, 20 nm
  • made of ribosomal RNA in nucleolus
  • free floating in cytoplasm or attached to ER, forming rough ER
  • no membrane + is the site of protein synthesis
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27
Q

What is the function of Ribosomes

A
  • ribosomes on RER mainly synthesis proteins that will be exported outside cell
  • ribosomes free floating are site of assembly of proteins that will be used inside the cell
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28
Q

What is the structure of Centrioles

A
  • consist of 2 tubes of microtubules
  • microtubules made of tubulin protein subunits and then arranged to form a cylinder
  • pair found next to nucleus in animal cells
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29
Q

What is the function of Centrioles

A
  • aid cell division: move to opposite poles of the cell as spindle develops
  • spindle, made from threads of tubulin, forms from centrioles
30
Q

What is the structure of Cilia + undulipodia

A
  • protrusions from the cell + surrounded by cell surface membrane
  • each contains microtubules
  • formed from centrioles
    > centrioles multiply + line up beneath cell surface membrane > microtubules sprout outwards from each centriole forming cilia or undulipodia
31
Q

What is the function of Cilia + undulipodia

A
  • epithelial cells lining airways have many cilia that move the mucus
  • nearly all cells have at least one cilium that acts as an antenna and contains receptors allowing cell to detect signals about its immediate environment
  • undulipodia = longer cilium
32
Q

What is the structure of Cellulose cell wall

A
  • cellulose cell wall of plants is on the outside of the plasma membrane
  • made from bundles of cellulose fibres, a complex carbohydrate
33
Q

What is the function of Cellulose cell wall

A
  • strong + can prevent plant cells from bursting when turgid
  • provides:
    > strength and support
    > maintains cells shape
    > permeable + allow solutions (solutes + solvents) to pass through
  • fungi have cell walls containing chitin, not cellulose
34
Q

What is the structure of cytoskeleton + what it consists of

A
  • present throughout cytoplasm of all eukaryotic cells
  • network of fibres necessary for the shape + stability of a cell
  • it consists of:
    > rod-like microfilaments made of subunits of protein actin (7nm)
    > intermediate filaments (10nm)
    > straight, cylindrical microtubules, made of protein subunits called tubulin (18-30nm)
35
Q

What is the function of microfilaments

A
  • cell movement, cell contraction during cytokinesis
    -support + mechanical strength + keep cells shape stable
36
Q

What is the function of microtubules

A
  • polymerise to form tubes that form scaffold like structure that determines the shape of a cell
  • act as tracks for movement of organelles around cells (incl vesicles)
  • microtubules form spindles that allow chromosomes to be separated in cell division
37
Q

What is the function of intermediate fibres

A
  • anchor the nucleus within the cytoplasm
    -give mechanical strength to cells and help maintain their integrity
38
Q

What is the radiation used for light microscope

A

Light rays

39
Q

What is the radiation used for electron microscope

A

Electron beams

40
Q

What do light microscopes focus with

A

Lenses

41
Q

What do electron microscopes focus with

A

Magnets

42
Q

What is the magnification for light microscopes

A

X1500

43
Q

What is the magnification for electron microscope

A

X500,000

44
Q

What is the resolving power for light microscope

A

200nm

45
Q

What is the resolving power for electron microscope

A

0.2nm

46
Q

What state does the biological matter have to be for light microscope

A

Living or dead

47
Q

What state does the biological matter have to be for electron microscope

A

Dead

48
Q

What is the size of light microscope

A

Small and portable

49
Q

What is the size of electron microscope

A

Very large and static

50
Q

What is the ease of use for light microscope

A

Easy to use

51
Q

What is the ease of use for electron microscopes

A

Skill and training required

52
Q

What is the cost of light microscope

A

Relatively cheap

53
Q

What is the cost of electron microscope

A

Very expensive

54
Q

Does the sample have to be in a vacuum for light microscope

A

No

55
Q

Does the sample have to be in a vacuum for electron microscope

A
  • yes
    > because if not the electrons could bounce off air particles etc
56
Q

Does the image in light microscope have colour

A

Yes

57
Q

Does the image in electron microscope have colour

A

Black + white

58
Q

What are the 2 types of electron microscopes

A
  • Transmission electron microscope (TEM)
  • Scanning electron microscope (SEM)
59
Q

What happens to the electron beams in TEM

A
  • beams of electrons pass through the very thin sample
60
Q

What happens to the electron beams in SEM

A

Electron beams are directed onto the sample

61
Q

How do the electrons produce an image in TEM

A

Electrons pass through denser parts more easily which creates contrast in the image

62
Q

How do the electrons produce an image in SEM

A

Electrons bounce off sample and become focused on the screen

63
Q

What is the type of image produced in TEM

A

2D

64
Q

What is the type of image produced in SEM

A

3D

65
Q

What is the magnification of TEM

A

X 500,000

66
Q

What is the magnification of SEM

A

X 200,000

67
Q

In TEM what has to happen to the specimen before being used

A
  • it has to be chemically fixed by being dehydrated and stained with metal salts
68
Q

What do confocal microscopes allow you to do

A
  • observe whole living specimens and can focus on structures at different depths within a specimen
69
Q

How do confocal microscopes work

A
  • the laser light scans the object point by point and assembles it by the computer putting the pixel information into one image
70
Q

What is an advantage of confocal microscopes

A
  • image is high in resolution and shows high contrast
71
Q

What is an advantage of confocal microscopes

A
  • image is high in resolution and shows high contrast

OCR A Level Biology A (6 decks)

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