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A Level - Biology > 3: Cell Structure > Flashcards

3: Cell Structure Flashcards

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1
Q

What is a nanometer in meters?

A

nm = m^-9

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2
Q

What is a micrometer

A

um = m^-6

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3
Q

What are the two types of microscopes?

A

Electron and light

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4
Q

What is the equation for magnification?

A

magnification = size of image / size of real object

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5
Q

What is the definition of magnification?

A

How many times bigger the image is in comparison to the object

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6
Q

What is resolution? (resolving power)

A

Minimum distance apart that two objects can be in order for them to appear separate

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7
Q

What is cell fractionation?

A

Process where cells are broken up and the different organelles they contained are separated out

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8
Q

What solution is required for cell fractionantion?

A

Cold, buffered, same water potential

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9
Q

Why does the solution for cell fractionantion have to be cold?

A

Reduce enzyme activity that might break down organelles

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10
Q

Why does the solution for cell fractionantion have to be buffered?

A

So the pH doesn’t fluctuate, as any change would cause a change in the organelle structure

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11
Q

What are the two steps of cell fractionation?

A

Homogenation and Ultracentrifugation

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12
Q

What is homogenation?

A

Cells are broken up by using a homogeniser (blender). Produces homogenate fluid, which is then filtered to remove large debris

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13
Q

What is Ultracentrifugation?

A

Homogenate is spun at very high speeds in order to create a centrifugal force and separate the different parts of the cell

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14
Q

What are the steps of Ultracentrifugation?

A

Tube of filtrate spun at low speed
Heaviest organelles (nuclei) are forced to the bottom where they form a sediment or pellet
Fluid at the top (supernatant) removed
Supernatant separately spun at faster speed
Mitochondria forms pellet, can be removed
Can be repeated for each organelle

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15
Q

What is the resolution of an optical microscope?

A

0.2 micrometer

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16
Q

What is the resolution of an electron microscope?

A

0.1 nanometers

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17
Q

Name some parts of the light microscope

A 
Eyepiece
Objective & Eyepiece lens
Stage
Diaphragm
Light Source
Base
Fine & Coarse adjustment
Arm 
Body Tube
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18
Q

What is the diaphragm of the microscope?

A

Allows different amounts of light to pass through the specimen

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19
Q

What speed of the centrifuge is needed to separate the nuclei?

A

1000 rpm

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20
Q

What speed of the centrifuge is needed to separate the mitochondria?

A

3500 rpm

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21
Q

What speed of the centrifuge is needed to separate the lysosomes?

A

16500 rpm

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22
Q

What is the supernatant?

A

The fluid at the top of the tube after the centrifuge process

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23
Q

What is the problem with a light microscope?

A

Poor resolution caused by relatively long wavelength of light

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24
Q

What are the two main advantages of an electron microscope?

A

High resolution - very short wavelength beam can be focused using electromagnets

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25
Q

What is the resolving power of a modern electron microscopes?

A

0.1nm

2000x better than light

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26
Q

Why does an electron microscope require a vacuum?

A

Absorbed or deflected in air

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27
Q

What are the two types of electron microscopes?

A

TEM - Transmission electron microscopeSEM - Scanning electron microscope

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28
Q

How does TEM work?

A 
Electron gun produces beam of electrons
Focused by condenser electromagnet
Beam passes through thin specimen
Thicker parts absorb them and are dark
Electrons form image
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29
Q

What is the resolving power of TEM?

A

0.1nm

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30
Q

What can be done with the image of a TEM?

A

Photographed to produce a photomicrograph

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31
Q

What are the limitations of TEM & SEM?

A

Vacuum so no live specimens can be observed
Complex staining must be required - image not in colour
Specimen must be extremely thin
Image might have artifacts

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32
Q

What is an artifact?

A

Things that are created during the specimen in preparation, can be difficult to point out

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33
Q

What type of image is produced by TEM?

A

2-D Image

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34
Q

Does SEM require an extremely thin specimen

A

No

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35
Q

How does a SEM work?

A

Directs a beam of electrons to the surface of a specimen
Beam is passed back and forth across a portion of the specimen in regular pattern
Electrons scattered by specimen, how they scatter depending on contours
Build a 3-D image by computer analysis of the pattern of scattered electrons and secondary electrons

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36
Q

What is the resolving power of SEM?

A

20 nm

Not as good as TEM but better than light

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37
Q

What is used in light microscopes to measure the size of objects?

A

Eyepiece graticule

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38
Q

What is an eyepiece graticule?

A

Glass disc with scale

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39
Q

What is the usual length of a eyepiece graticule?

A

10mm

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40
Q

How many subdivisions are typically on an eyepiece graticule?

A

100

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41
Q

Why can the graticule not be used directly?

A

Different objective lenses have different magnifications

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42
Q

What is needed to calibrate the eyepiece graticule?

A

Stage micrometer

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43
Q

What is the size of the stage micrometer?

A

2mm

Sub-divisions are 0.01mm or 10um

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44
Q

How do you calibrate the eyepiece graticule?

A

Note how many divisions of a stage micrometer equal a number of epg divisons
1 stage micrometer subdivision = 10um
Work out epgu in um

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45
Q

What is the ultra-structure?

A

Internal structure of a cell which suits its function

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46
Q

What is a eukaryotic cell?

A

They have a distinct nucleus and have membrane-bound organelles

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47
Q

What is the diameter of a nucleus?

A

10-20um diamater (average)

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48
Q

What are the functions of the nucleus?

A

Controls cell through production mRNA and tRNA
Retain genetic information of cell
Manufacture ribosomal RNA and ribosomes

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49
Q

What are the sub parts of the nucleus?

A 
Nuclear envelope
Nuclear pores
Nucleoplasm
Chromosomes
Nucleolus
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50
Q

What forms of genetic material is found in a nucleus?

A

DNA and chromosomes

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51
Q

What is the nuclear envelope?

A

Double membrane that surrounds the nucleus.
Controls entry and exit of materials
Contains reactions taking place
Continuous with ER

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52
Q

What are nuclear pores?

A

Allows passage of large molecules (RNA)

Around 3000 pores each 40-100nm in diameter

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53
Q

What is the nucleoplasm?

A

Granular, jelly-like material that makes up the majority of the nucleus

54
Q

What are chromosomes?

A

Consists of protein bound, linear DNA

55
Q

Where is the nucleolus?

A

Small spherical region in the nucleoplasm ( can be more than one)

56
Q

What is the function of the nucleolus?

A

Manufactures ribosomal RNA and assembles ribosomes

57
Q

What is the endoplasmic reticulum?

A

3-D system sheet-like membrane

Encloses a network of tubules and cisternae (flattened sacs)

58
Q

What are the two types of endoplasmic reticulum?

A

Rough Endoplasmic Reticulum (RER)

Smooth Endoplasmic Reticulum (SER)

59
Q

What is the difference between RER and SER?

A

RER has ribosomes present on the outer surface of membranes.
SER has no ribosomes

60
Q

What are the functions of the RER?

A

Provides a large surface area for the synthesis of proteins & glycoproteins

61
Q

What are the functions of SER?

A

Synthesise, store and transport lipids & carbohydrates

62
Q

What are ribosomes?

A

Small cytoplasmic granules found in RER and cytoplasm

The site of protein synthesis

63
Q

What are the two types of ribosomes?

A

80S - in eukaryotic cells, around 25nm in diameter

70S - prokaryotic cells, mitochondria and chloroplasts and smaller

64
Q

What are ribosomes made from?

A

Composed of ribosomal RNA and protein

65
Q

What is the structure of the golgi apparatus/body?

A

Cisternae (flattened sacs) with vesicles (small rounded hollow structures)

66
Q

What are the functions of the golgi apparatus/body?

A 
Modifies proteins so it canadd carbohydrates or lipids to proteins
Produce secretory enzymes
Form lysosomes
Labels proteins
Transport modify and store lipids
67
Q

What happens to the modified proteins in the golgi apparatus/body?

A

Transported to vesicles for exocytosis, and remove them from the cell

68
Q

In which type of cells is the golgi apparatus/body very common?

A

Secretory cells(epithelial cells that line the intestines)

69
Q

How are lysosomes formed?

A

When vesicles produced by the golgi body contain enzymes

70
Q

What are the enzymes found in lysosomes?

A

Proteases, lipases, and lysozymes (50 enzymes total)

Up to 1um in diameter

71
Q

What are the functions of lysosomes?

A

Hydrolyse material by ingested by phagocytic cells (white blood cells)
Release enzymes to outside the cell (exocytosis) to destroy material
Digest worn out organelles Completely break down cells after they have died (autolysis)

72
Q

What is the structure of the mitochondria?

A

Rod-shaped and 1-10um in length
Double membrane
Cristae
Matrix

73
Q

What does the double membrane do in the mitochondria?

A

Controls entry and exit of material

74
Q

What does the cristae do in the mitochondria?

A

Folded inner membrane provides a large surface area for the attachment of enzymes and other respirational proteins

75
Q

What does the matrix do in the mitochondria?

A

Fluid containing protein, own lipids, ribosomes and mDNA.
Allows mitochondria to control production of own proteins
Respirational enzymes found here

76
Q

What is the function of a mitochondria?

A

Site of aerobic respiration

Responsible for production of ATP

77
Q

What are the features of the cell wall?

A 
Consists of polyssacharides
Thin layer (middle lamella) which marks boundary between adjacent cell walls and cements cells together
78
Q

What are the functions of the cell wall?

A

Provide mechanical strength to prevent cell bursting under pressure by osmotic entry of water
Gives mechanical strength to plant as a whole
Allow water to pass along it and contribute to the movement of water

79
Q

What are the cell walls of fungi made from?

A

Chitin

80
Q

What are the cell walls in algae made from?

A

Cellulose or glycoproteins or a mix

81
Q

What are the features of chloroplasts?

A

Carries out photosynthesis Disc. shaped 2-10um long and 1um in diameter

82
Q

What is the structure of the chloroplasts?

A

Chloroplast envelope
Thylakoids stacked to make grana
Stroma matrix

83
Q

What is the chloroplast envelope?

A

Double plasma membrane that surrounds the organelle, decides what enters and leaves the cell

84
Q

What is a thylakoid?

A

Disc shaped structure that contains chlorophyll which stack to form grana where 1st stage of photosynthesis occurs

85
Q

What is the stroma?

A

Fluid filled matrix where 2nd stage of photosynthesis occurs

Contains a large number of starch grains

86
Q

How are they adapted to photosynthesis?

A

Granal membranes provide a large surface area for attachment of chlorophyll
Fluid of stroma has enzymes needed to make sugars for the 2nd stage
Ribosomes and DNA so they can manufacture proteins for photosynthesis

87
Q

What is a vacuole?

A

Fluid filled sac bound by a single membrane (tonoplast)

88
Q

Where is a vacuole found?

A

One large central vacuole in a plant cell

89
Q

What does a vacuole contain?

A 
Mineral salts
Sugars
Amino acids
Wastes
Pigments
90
Q

What are the functions of the vacuole?

A

Support herbaceous parts of woody plants, by making cells turgid
Sugars and amino acids act as a temporary food store
Pigments may colour petals to attract pollinating insects

91
Q

How can you tell the function of the cell?

A

Number and size of organelles

92
Q

What is murein?

A

Polymer of disaccharides

Provides mechanical strength in cell walls

93
Q

Are vacuoles found in animal cells?

A

Yes, however they are much smaller

94
Q

What is the ultra-structure?

A

Internal structure of a cell which suits its function

95
Q

What is a eukaryotic cell?

A

They have a distinct nucleus and have membrane-bound organelles

96
Q

What is the diameter of a nucleus?

A

10-20um diamater (average)

97
Q

What forms of genetic material is found in a nucleus?

A

DNA and chromosomes

98
Q

What are ribosomes?

A

Small cytoplasmic granules found in RER and cytoplasm

The site of protein synthesis

99
Q

What are the two types of ribosomes?

A

80S - in eukaryotic cells, around 25nm in diameter

70S - prokaryotic cells, mitochondria and chloroplasts and smaller

100
Q

How common are mitochondria?

A

Occur in vast numbers

Account for around 25% of the dry mass of a cell

101
Q

What is the structure of the golgi apparatus/body?

A

Cisternae (flattened sacs) with vesicles (small rounded hollow structures)

102
Q

What is the function of a mitochondria?

A

Site of aerobic respiration

Responsible for production of ATP

103
Q

What do cell walls consist of?

A

Microfibrilis of the polyssacharides, embedded in a matrix

104
Q

What are the features of the cell wall?

A 
Consists of polyssacharides
Thin layer (middle lamella) which marks boundary between adjacent cell walls and cements cells together
105
Q

What are the functions of the vacuole?

A

Support herbaceous parts of woody plants, by making cells turgid
Sugars and amino acids act as a temporary food store
Pigments may colour petals to attract pollinating insects

106
Q

How can you tell the function of the cell?

A

Number and size of organelles

107
Q

What is the order of the composition of an organism?

A

Organism -> Organ System -> Organs -> Tissues -> Cells

108
Q

What type of cells for a tissue?

A

1 type of cells

109
Q

What type of tissues form an organ?

A

Multiple tissues

Same function

110
Q

Why are cells specialized?

A

Provide the best conditions for all functions

111
Q

How are cells specialized?

A

Only some genes are activated (expressed) in the cells defining the cell

112
Q

What is epithelial tissue?

A

Sheets of cells that line cells which are either protective or secretory function

113
Q

What is a stem cell?

A

Cell which can differentiate

114
Q

What are the three levels of stem cells?

A

Totipotent
Pluripotent
Unipotent

115
Q

What does totipotent mean?

A

Cells can differentiate into any type of cell

116
Q

What does pluripotent mean?

A

Can differentiate into many types of cell but not all

117
Q

What does unipotent mean?

A

Cell can only replicate themselves

118
Q

What is a prokaryotic cell?

A

Small cells and no nucleus or membrane bound organelles

119
Q

What is the size of a bacteria?

A

0.1-10um in length

120
Q

What is the cell wall made up of in bacteria?

A

Murein

121
Q

What ribosomes are found in the bacteria?

A

70S

122
Q

What is found in a bacteria cell?

A 
Pilus
Cell Wall
Capsule
Cell membrane
Plasmid
Flagellum
Ribosomes
Nucleiod 
Cytoplasm
123
Q

What is a cell capsule made of?

A

Mucilaginous layer

124
Q

What is the role of the capsule?

A

Protects bacterium from other cells and helps groups of bacteria to stick together for further protection

125
Q

What is the purpose of circular DNA?

A

Possesses genetic material info for replication of cells

126
Q

What is the role of the plasmid?

A

Possesses genes that may aid the survival of bacteria in adverse conditions

127
Q

What is the size of virus cells?

A

20-300nm

128
Q

What are the contents of a virus?

A

Nucleic acids
Capsid
Attachment proteins

129
Q

What nucleic acids are found in viruses?

A

RNA and DNA

130
Q

What is the capsid?

A

Protein coat

131
Q

What virus has a lipid envelope?

A

Human immunodeficiency virus

132
Q

Where and what are attachment proteins?

A

In the capsid

Allows the virus to identify and attach to a host cell

A Level - Biology (22 decks)

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