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topic 2 - cells and viruses Flashcards

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1
Q

what does cell theory state?

A

cells are a fundamental unit of structure, function and organisation in all living organisms

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2
Q

what magnification can a light microscope do?

A

x1500

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3
Q

what magnification can an electron microscope do?

A

x50,000

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4
Q

define magnification

A

how many times bigger than image is than the real thing

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5
Q

define resolution

A

measure of how close two objects can be before we see them as one

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6
Q

what does haematoxylin do? (stain)

A

stains nuclei purple/blue/brown

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7
Q

what does methylene do? (stain)

A

stains nuclei blue

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8
Q

what does acetocarmine do? (stain)

A

stains chromosomes in dividing nuclei

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9
Q

what does iodine do? (stain)

A

stains starch containing material (in plants) blue/black

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10
Q

what are the advantages of a light microscope?

A

can see living specimens
cheap
portable

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11
Q

what are the disadvantages of light microscopes?

A

preservation can cause artefacts
limited resolution and magnification

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12
Q

name a stain that can be used to show the different stages of mitosis

A

orcein

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13
Q

advantages of electron micrographs

A

high magnification and resolution
see very detailed image

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14
Q

disadvantages of electron micrographs

A

specimens are dead (vacuum)

treatments- artefacts and very skilled work

expensive

large- need constant temp and pressure

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15
Q

how can you make a specimen more visible?

A

warm to intensify stain
tease cells apart
add stain

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16
Q

what does the cell surface membrane do?

A

controls what enters/leaves the cell

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17
Q

why do some membranes need to be able to break/fuse easily?

A

to allow vesicles (carrying chemical secretions) out of the cell

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18
Q

what are membranes mainly made from?

A

lipids and proteins

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19
Q

what are polar lipids?

A

lipid molecules with one end joined to a polar group

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20
Q

how does the proportion of phospholipids unsaturated containing fatty acids affect the fluidity of the membrane?

A

the more unsaturated fatty acids, the more fluid it is because they are kinky so are liquid at room temperature

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21
Q

what are gated channels?

A

channels that can open/shut depending on the conditions of the cell

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22
Q

what is the protoplasm?

A

combination of cytoplasm and nucleus

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23
Q

give examples of what cell membranes do

A

controls what enters/leaves
localises enzyme pathways

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24
Q

what is the affect of the nucleus having pores?

A

allows chemicals to pass in/out so nucleus can control reactions

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25
Q

what substances are inside the nuclear envelope?

A

nucleic acids and proteins

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26
Q

what are the nucleic acids?

A

DNA and RNA

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27
Q

when the cell is not actively dividing, what does DNA bind to?

A

chromatin

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28
Q

what is the nucleolus and what is it involved in?

A

the nucleolus is an area in the nucleus containing extra dense DNA and protein

it is involved in the production of ribosomes

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29
Q

how many membranes does a mitochondria have?

A

two- an out and inner membrane

inner membrane- folded- larger SA

surrounded by fluid matrix

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30
Q

what is special about mitochondria and DNA?

A

mitochondria contain their own genetic material so when a cell divides, mitochondria replicate themselves

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31
Q

what is a centriole made from?

A

9 tubules

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32
Q

what is the role of the centrioles?

A

involved in cell division
pull apart to create spindle of microtubules- these are involved in the movement of chromosomes

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33
Q

what is the cytoskeleton?

A

3D web like structure
contains microfilaments and microtubules

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34
Q

what is the function of the cytoskeleton?

A

gives cytoplasm structure
keeps organelles in place
cell movement and transport

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35
Q

what are contractile vacuoles?

A

vacuoles that empty/fill to help maintain concentration of cytoplasm (in freshwater animals)

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36
Q

where are thylakoids found?

A

chloroplasts

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37
Q

what is translocation?

A

when part of a chromosome breaks off and attaches to another chromosome

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38
Q

what is the type of chromosome mutation that results in Down’s syndrome?

A

non-disjunction

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39
Q

what ribosomes do eukaryotic cells contain?

A

80s ribosomes

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40
Q

what are the two subunits for 80s ribosomes?

A

60s and 40s

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41
Q

what are the two subunits for 70s ribosomes?

A

30s and 50s

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42
Q

what is the function of the RER?

A

isolates and transports proteins (once they’ve been made by the ribosomes)

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43
Q

what is the role of the SER?

A

synthesis and transport of lipids and steroids

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44
Q

what is the golgi apparatus made from?

A

lots of flatterned stacks of cisternae

(formed by vesicles from ER fusing together)

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45
Q

what does the golgi apparatus do?

A

proteins brought there (that have pinched off ER)

vesicles fuse with membrane sacs of golgi apparatus and proteins enter

as they travel through, the proteins are modified

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46
Q

what is the role of lysosomes?

A

contain enzymes that break down molecules

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47
Q

what is apoptosis?

A

controlled cell death- lysosomes release their contents

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48
Q

what is the first layer to form when a plant cell divides?

A

middle lamella

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49
Q

explain how calcium pectate is formed

pectin has n….. charged car….. groups

these combine with positive calcium ions to form ……

this binds to the cellulose that forms on either side

A

pectin has negatively charged carboxyl groups

these combine with positive calcium ions to form calcium pectate

this binds to the cellulose that forms on either side

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50
Q

what is the difference between the primary and secondary cell wall?

A

primary: more flexible, microtubules are all laying in same direction

secondary: more built up, more rigid, microtubules are laying at different angles- hemicelluloses harden it further

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51
Q

what is added to cell walls to produce wood?

A

lignin

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52
Q

what are plant fibres? uses?

A

long cells in cell walls that have been heavily lignified - used in clothing/ropes/paper

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53
Q

what are plasmodesmata?

A

cytoplasm bridges which allow for communication between cells

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54
Q

what is the symplast?

A

the interconnected cytoplasm of the cells

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55
Q

what happens in exocytosis?

A

vesicle fuses with cell surface membrane and substances exits the cell

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56
Q

what is a vacuole?

A

a fluid filled space inside the vacuole with a cell membrane

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57
Q

how frequently do vacuoles form in animal cells?

A

vacuoles form frequently in animal cells but they are only temporary and therefore only for, when they are needed

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58
Q

what is a vacuole’s membrane called?

A

tonoplast

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59
Q

what is the vacuole filled with?

A

cell sap- causes water to move into cell by osmosis so keeps vacuole pressed up against cell wall

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60
Q

briefly describe the order of organisation

A

organ system

organ

tissue

cells

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61
Q

define ‘tissue’

A

group of cells that work together to perform the same function

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62
Q

what are the four main tissue types?

(in human body)

A

epithelial tissue
connective tissue
nervous tissue
muscle tissue

63
Q

where may you find squamous epithelium?

A

lining surface of blood vessels

forms wall for capillaries and alveoli

64
Q

what do cuboidal and columnal cells do?

A

line tubes in the body

65
Q

what is the role of ciliated epithelia?

A

contain goblet cells that produce mucus

form surface of tubes in gas exchange

cilia moving from side to side move substances along

66
Q

where is compound epithelia found?

A

where the skin is continually scratched

67
Q

define ‘organ’

A

several tissues that work together to carry out a particular function

68
Q

what is meant by bacterial cell walls being ‘hypertonic’ to the medium around them?

A

water moves in by osmosis
cell wall prevents cell from swelling and bursting

69
Q

describe the structure of peptidoglycan

A

many chains
peptide crosslinkages
net like structure

70
Q

what makes up all bacterial cell walls?

A

peptidoglycan

71
Q

what does a slime capsule/layer do?

A
  1. protects the cell from phagocytosis
  2. covers cell markers (on membrane)-

easier for cell to be pathogenic (cause disease)

as it can’t be as easily identified by immune system

72
Q

what may the slime capsule be made from?

A

starch/glycolipid/protein/gelatin

73
Q

what are pili?

A

protein projections from cell surface

74
Q

what are pili used for?

A

attachment to host cell in sexual reproduction

make bacteria more vulnerable to viral infections - bacteriophage can use pili as an entrance point

75
Q

what is the flagella used for in bacteria cells?

A

a flagella is present so that a bacteria can move itself (using rapid rotations)

76
Q

bacteria have no mitochondria, so what is used as the respiratory site?

A

cell membrane

77
Q

what is the nucleoid?

A

area in bacterial cell where tangled DNA is found

78
Q

how can bacterial cell walls be identified?

A

gram staining

79
Q

why is gram staining effective?

A

different types of bacteria are vulnerable to different types of antibiotics

80
Q

describe the cell walls of gram POSITIVE bacteria

A

think layer of peptidoglycan - containing teichoic acid within net like structure

81
Q

explain the testing of gram positive bacteria

A

crystal violet + iodine is trapped in peptidoglycan layer

resists decolouring when dehydrated with alcohol

doesn’t pick up red counter stain

leaving positive purple colour

82
Q

describe the structure of gram NEGATIVE bacteria cell walls

A

thin layer of peptidoglycan

no teichoic acid

outer membrane is made from lipopolysaccharides

83
Q

explain the testing process for gram NEGATIVE bacteria

A

crystal violet + iodine added
dehydrated with alcohol- lipopolysaccharide layer dissolves in ethanol
leaves thin layer of peptidoglycan wall exposed

crystal violet + iodine is washed out

red counterstain is picked up by peptidoglycan so appears red

84
Q

why is it important for doctors to know if a bacteria is gram positive or gram negative?

A

this determines which antibiotic is given

85
Q

what do beta-lactam antibiotics do?

which type of bacteria would this be most effective against?

A

beta-lactam antibiotics inhibit the formation of peptidoglycan in the cell wall

(therefore very effective against gram-positive bacteria as this is vital to their structure)

86
Q

explain what glycopeptide antibiotics do and what type of bacteria they are effective against

A

glycopeptide antibiotics are large molecules

effective against gram-positive

not effective against gram-negative because they can’t penetrate the outer membrane

87
Q

explain how polypeptide antibiotics work and against which type of bacteria

A

very effective against gram-negative bacteria because they interact with the phospholipids on outer membrane

88
Q

what shape are cocci bacteria?

A

spherical

89
Q

what shape are bacilli bacteria?

A

rod shaped

90
Q

what shape are spirilla bacteria?

A

twisted

91
Q

what shape are vibrios bacteria?

A

comma shaped

92
Q

describe what obligate aerobes are

A

obligate aerobes are bacteria that need oxygen (for respiration)

93
Q

describe what facultative aerobes are

A

bacteria that use oxygen if available but can also survive without

94
Q

describe what obligate anaerobes are

A

bacteria that only respire in the absence of oxygen

(die in the presence of oxygen)

95
Q

what is a viruses capsid (protein coat) made from?

what is the adv of it using repeating units?

A

repeating protein units called capsomeres.

using repeating units minimises the amount of genetic material needed to code for the capsid

96
Q

some viruses have a lipid envelope.

what is the adv/disadv of this?

A

advantage of lipid envelope is it makes it easier for virus to pass between cells

disadvantage of lipid envelope is it makes virus vulnerable to substances

(eg ‘ether’ which dissolves membrane)

97
Q

how do viruses attach to their host cells?
what do these do?

A

using VAPs (virus attachment particles)

the VAPs target the proteins in the host cell

98
Q

describe how a DNA virus works

A

genetic material is DNA

viral DNA is used as a template for new viral DNA

also used as template to produce viral mRNA in protein synthesis

99
Q

Give examples of DNA viruses

A

small pox
adenovirus (common cold)
bacteriophages (lambda phage)

100
Q

describe how a RNA virus works

explain the difference between positive and negative ssRNA- give examples of viruses caused by each

A

contain single strand RNA (ssRNA)

positive ssRNA act as mRNA and can be directly translated by the ribosomes (eg polio/TMV)

negative ssRNA can not be directly translated - must be transcribed first
(eg measles/ibfluenza/ebola)

101
Q

explain how RNA retroviruses work

A

have protein capsid and lipid envelope

single strand of RNA directs the synthesis of enzyme called reverse transcriptase

this makes DNA molecules corresponding to the viral genome

DNA is then incorporated into host cell DNA and used as a template (eg HIV and some leukaemia)

102
Q

what are bacteriophages?

A

viruses that attack bacteria

103
Q

how do bacteriophages infect?

A

they inject their viral material into the host cell (but the bulk of it stays outside the cell)

the viral DNA forms a plasmid within the bacterium

104
Q

when DNA viruses enter a cell, they are non-virulent. what is meant by this?

A

non-virulent means they are non-disease causing when they first get into the cell

105
Q

what occurs in the lysogenic pathway?

A

viral DNA is injected and is replicated every time host cell divides
virus is non-virulent (not causing disease)
mRNA can’t be produced because one of the viral genes causes a repressor protein
repressor protein prohibits DNA from being translated into mRNA

106
Q

what is meant by lysogeny?

A

when virus is part of reproducing cells but is not causing an affect yet. said to be ‘latent’

107
Q

what is the lytic pathway?

A

process of replicating and killing cells

108
Q

describe what happens when viruses enter host cells and viral genetic material can be replicated independently.

A

viral genetic material is replicated as soon as it enters host

mature viruses are made, host cell bursts and releases virus particles (ready to invade other cells)

109
Q

what may happen when a host cell is damaged? (regarding what type of pathway it is on?)

A

when a host cell is damaged, may be activated from lysogenic to lytic. this is because the amount of repressor proteins decreases

110
Q

describe how positive ssRNA viruses replicate themselves

A

ssRNA contain single strand of RNA

used as mRNA for translation into proteins at ribosomes

111
Q

describe how negative ssRNA viruses replicate themselves

A

single antisense strand
needs to be translated into sense strand

uses RNA replicase- takes free bases from host cell to make sense strand

once translated, sense strand is used to make proteins at ribosomes

112
Q

explain how RNA retroviruses are replicated

A

contain viral RNA- can’t be used as mRNA

reverse transcriptase is used to translate RNA into DNA

viral DNA enters host DNA

transcriptase enzymes (in host) make viral RNA and mRNA

new viral material is synthesised

viral particles leave cell by exocytosis

113
Q

how can foot and mouth disease spread?

A

body secretions (milk/semen)
breath of infected animals
contamination (of food/water)

114
Q

how does ebola spread from animals to humans?

A

faeces, meat, blood, urine (of infected animals)

then spreads between humans through blood, contaminated surfaces (eg bedding) ,faeces, fluids

115
Q

what do antiviral treatments aim to do?

A

antiviral treatments aim to stop viral replication

116
Q

explain how antiviral treatment may work:

-target the ? which viruses use to recognise host cell

-target ? which are used to replicate DNA/RNA

-inhibit ? enzymes which enable new virus particles to bud from host membranes

A

target markers so virus can’t recognise host cell

target enzymes which are used for viral replication

inhibit protease enzymes which stop viral particles from budding from host membranes

117
Q

what are the symptoms of ebola?

A

fever and internal bleeding

118
Q

explain the difference between an epidemic and a pandemic.

A

an epidemic is when there are more expected cases of a disease in one place whereas a pandemic is when there is an epidemic happening in several countries

119
Q

suggests ways that disease can be controlled

A

rapid identification of disease
sterilising equipment
isolating victims
tracking people who have been in contact with victims
protective clothing
preventing transmission through good hygiene

120
Q

state the stages in drug development

A

early phase research
pre clinical testing
clinical trials
regulatory review
scale up to manufacturing
post market surveillance

121
Q

give suggestions of possible things to consider when evaluating whether a drug should be fast tracked

A

effectiveness of other treatments
effectiveness of normal disease control methods

122
Q

suggests criticisms of using an untested drug

A

side effects
seen as unethical
informed consent- dying people want it but relatives may then blame it for the death

123
Q

how could antibiotic treatment be used to identify if a bacterium is gram positive or gram negative?

A

if antibiotic worked , gram positive

gram positive has a cell wall with more peptidoglycan , this is a target site for the antibiotic

124
Q

What does the cell cycle produce?

A

two genetically identical daughter cells

125
Q

What are the three stages of the cell cycle and what do each of these consist of?

A

interphase - G1, S, G2
mitosis - P M A T
cytokinesis

126
Q

interphase consists of G1, S , G2 phase.

What occurs in each of these stages?

A

G1- organelles replication, lots of transcription and translation (many proteins needed)

S- synthesis of DNA so that chromosomes can be replicated

G2-growth, transcription, translation, replaces energy stores lost in S, fixes any damaged DNA

127
Q

describe the stages of mitosis

A

Prophase
Chromosomes condense to become more visible
Centrioles move to opposite ends of cells and microtubules are made to form spindle
Nuclear envelope and nucleolus disappear

Metaphase
Centrioles line up across equator of spindle

Anaphase
Early anaphase: centromeres divide in two/microtubules contact so chromatids separate
Late anaphase: chromatids move to opposite poles- using energy provided by mitochondria

Telophase
Daughter chromatids reach poles and uncoil to form chromatin
Spindle fibres disintegrate
Nuclear envelope and nucleolus reform

128
Q

purpose of mitosis

A

growth and repair

129
Q

examples of asexual reproduction

A

budding/binary fission/vegetative propagation

130
Q

what happens in cytokinesis?

A

Cell membrane pulled in by cytoskeleton

Creates furrow which deepens

Cytoplasm is split, forming two identical daughter cells

131
Q

stages of meisosis

A

Prophase 1
Chromosomes condense and become visible
Nuclear envelope and nucleolus disintegrates
Centrioles move to opposite ends of cell
Spindle fibres form from microtubules on centrioles
Crossing over takes place (creating genetic variation)

Metaphase 1
Chromosomes line up at equator (attached to centrioles at centromere of chromosome)
Independent assortment

Anaphase 1
Chromosomes are pulled to opposite ends of cell

Telophase 1
Nuclear envelope and nucleolus reform
Chromosomes become invisible again
Spindle fibre disintegrates
Chromosome number in each cell Is half that of the original

INTERPHASE
No further replication of DNA

Prophase 2
Chromosomes condense and become visible
Nuclear envelope and nucleolus disintegrates
Centrioles move to opposite ends of cell
Spindle fibres form from microtubules on centrioles
Crossing over takes place (creating genetic variation)

Metaphase 2
Chromosomes line up at equator (attached to centrioles at centromere of chromosome)
Independent assortment

Anaphase 2
Chromosomes are pulled to opposite ends of cell

Telophase 2
Nuclear envelope and nucleolus reform
Chromosomes become invisible again
Spindle fibre disintegrates
Chromosome number in each cell Is half that of the original

CREATES FOUR HAPLOID CELLS

132
Q

name and explain the features of sperm

A

Shape
Allows sperm to be streamline and penetrate through the membrane of the egg

Flagella
Allows the sperm to move

Acrosome
Contains digestive enzymes which allows sperm to digest the membrane (zona pellucida) of the egg and fertilise it

Mitochondria
Makes ATP, gives sperm energy so it can swim/be mobile

133
Q

name and explain the features of an egg

A

Large
Increases chance of sperm entering and carries nutrients needed for fertilisation

Zona pellucida
releases cortical granules which solidifies corona radiata so no more sperm can get in (prevents polyspermy)

Corona radiata
Contains proteins, protect cell, stopping more sperm entering

134
Q

explain how stopping the proper formation of spindle fibres can stop cells dividing.

A

fibres are unable to contract

chromosomes can not be pulled to opposite ends of cell

new cells can not be made

135
Q

in which stage of the cell cycle does DNA replication occur?

A

interphase

136
Q

explain how male gametes are formed in plants

A

Diploid microspore undergoes meiosis

Forms haploid pollen tetrad

Microscpore’s nucleus migrates

Mitosis 1

Forms pollen grain (with generative nulceus and tube nucleus)

Generative nucleus undergoes mitosis to form two male gamete nuclei

137
Q

explain how female gametes are formed in plants

A

Ovule: diploid megaspore in mother cell, undergoes meiosis

Forms 4 haploid cells

Three die

One remaining now called ‘embryo sac’

Embryo sac undergoes mitosis three times

Forms 8 haploid nuclei (6 surrounded by membrane, 2 are not- these two are polar nuclei)

One of the 6 becomes the egg cell

138
Q

explain this type of asexual reproduction:

sporulation

A

Mitosis and production of asexual spores

ferns/mosses/fungi

139
Q

explain this type of asexual reproduction:

regeneration

A

Replacing parts of the body which have been lost

140
Q

explain this type of asexual reproduction:

fragmentation

A

Reproduce themselves asexually from fragments of their own body

141
Q

explain this type of asexual reproduction:

budding

A

Outgrowth from parental organism, which produces identical but smaller organisms

142
Q

explain this type of asexual reproduction:

vegetative propagation

A

Plant forms a structure which develops into a totally differntiated new plant

Identical to parent but eventually becomes independent

bulbs/running

143
Q

what is a feature of all RNA viruses ?

A

surrounded by a protein coat

144
Q

name some RNA viruses

A

ebola

TMV

145
Q

do bacteria , viruses or both have nucleic acid?

A

both

146
Q

do bacteria , viruses or both have cytoplasm?

A

bacteria only

147
Q

do bacteria , viruses or both have protein capsid?

A

virus only

148
Q

How does a DNA virus work?

A

infects bacterial cell
takes over reproductive system to make new viral proteins
used to build new viruses
lyses, kills the cell and infects new cells

149
Q

name a DNA virus

A

lambda phage

150
Q

What is the difference between positive ss RNA virus and negative ss RNA virus?

A

positive single strand - can be inserted straight into the host cell’s mechanism

negative single strand- strand needs to be transcribed into positive sense strand first

151
Q

give an example of an RNA retrovirus

A

HIV

152
Q

describe how an RNA retrovirus works

A

it is a double strand of RNA

has ability to reverse transcribe RNA into DNA (using reverse transcriptase)
can integrate newly created DNA into host cell’s DNA

153
Q

What does HIV target?

A

CD4 t lymphocytes (host cell)

causes immune response - T-killer now kill T-lymphocytes as they have the virus in it

154
Q

What bacteria is Tb caused by?

A

Mycrobacterium tuberculosis

biology (9 decks)

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