topic 2 - cells and viruses Flashcards
1
Q
what does cell theory state?
A
cells are a fundamental unit of structure, function and organisation in all living organisms
2
Q
what magnification can a light microscope do?
A
x1500
3
Q
what magnification can an electron microscope do?
A
x50,000
4
Q
define magnification
A
how many times bigger than image is than the real thing
5
Q
define resolution
A
measure of how close two objects can be before we see them as one
6
Q
what does haematoxylin do? (stain)
A
stains nuclei purple/blue/brown
7
Q
what does methylene do? (stain)
A
stains nuclei blue
8
Q
what does acetocarmine do? (stain)
A
stains chromosomes in dividing nuclei
9
Q
what does iodine do? (stain)
A
stains starch containing material (in plants) blue/black
10
Q
what are the advantages of a light microscope?
A
can see living specimens
cheap
portable
11
Q
what are the disadvantages of light microscopes?
A
preservation can cause artefacts
limited resolution and magnification
12
Q
name a stain that can be used to show the different stages of mitosis
A
orcein
13
Q
advantages of electron micrographs
A
high magnification and resolution
see very detailed image
14
Q
disadvantages of electron micrographs
A
specimens are dead (vacuum)
treatments- artefacts and very skilled work
expensive
large- need constant temp and pressure
15
Q
how can you make a specimen more visible?
A
warm to intensify stain
tease cells apart
add stain
16
Q
what does the cell surface membrane do?
A
controls what enters/leaves the cell
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
18
Q
what are membranes mainly made from?
A
lipids and proteins
19
Q
what are polar lipids?
A
lipid molecules with one end joined to a polar group
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
21
Q
what are gated channels?
A
channels that can open/shut depending on the conditions of the cell
22
Q
what is the protoplasm?
A
combination of cytoplasm and nucleus
23
Q
give examples of what cell membranes do
A
controls what enters/leaves
localises enzyme pathways
24
Q
what is the affect of the nucleus having pores?
A
allows chemicals to pass in/out so nucleus can control reactions
25
what substances are inside the nuclear envelope?
nucleic acids and proteins
26
what are the nucleic acids?
DNA and RNA
27
when the cell is not actively dividing, what does DNA bind to?
chromatin
28
what is the nucleolus and what is it involved in?
the nucleolus is an area in the nucleus containing extra dense DNA and protein
it is involved in the production of ribosomes
29
how many membranes does a mitochondria have?
two- an out and inner membrane
inner membrane- folded- larger SA
surrounded by fluid matrix
30
what is special about mitochondria and DNA?
mitochondria contain their own genetic material so when a cell divides, mitochondria replicate themselves
31
what is a centriole made from?
9 tubules
32
what is the role of the centrioles?
involved in cell division
pull apart to create spindle of microtubules- these are involved in the movement of chromosomes
33
what is the cytoskeleton?
3D web like structure
contains microfilaments and microtubules
34
what is the function of the cytoskeleton?
gives cytoplasm structure
keeps organelles in place
cell movement and transport
35
what are contractile vacuoles?
vacuoles that empty/fill to help maintain concentration of cytoplasm (in freshwater animals)
36
where are thylakoids found?
chloroplasts
37
what is translocation?
when part of a chromosome breaks off and attaches to another chromosome
38
what is the type of chromosome mutation that results in Down's syndrome?
non-disjunction
39
what ribosomes do eukaryotic cells contain?
80s ribosomes
40
what are the two subunits for 80s ribosomes?
60s and 40s
41
what are the two subunits for 70s ribosomes?
30s and 50s
42
what is the function of the RER?
isolates and transports proteins (once they've been made by the ribosomes)
43
what is the role of the SER?
synthesis and transport of lipids and steroids
44
what is the golgi apparatus made from?
lots of flatterned stacks of cisternae
(formed by vesicles from ER fusing together)
45
what does the golgi apparatus do?
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
46
what is the role of lysosomes?
contain enzymes that break down molecules
47
what is apoptosis?
controlled cell death- lysosomes release their contents
48
what is the first layer to form when a plant cell divides?
middle lamella
49
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
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
50
what is the difference between the primary and secondary cell wall?
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
51
what is added to cell walls to produce wood?
lignin
52
what are plant fibres? uses?
long cells in cell walls that have been heavily lignified - used in clothing/ropes/paper
53
what are plasmodesmata?
cytoplasm bridges which allow for communication between cells
54
what is the symplast?
the interconnected cytoplasm of the cells
55
what happens in exocytosis?
vesicle fuses with cell surface membrane and substances exits the cell
56
what is a vacuole?
a fluid filled space inside the vacuole with a cell membrane
57
how frequently do vacuoles form in animal cells?
vacuoles form frequently in animal cells but they are only temporary and therefore only for, when they are needed
58
what is a vacuole's membrane called?
tonoplast
59
what is the vacuole filled with?
cell sap- causes water to move into cell by osmosis so keeps vacuole pressed up against cell wall
60
briefly describe the order of organisation
organ system
organ
tissue
cells
61
define 'tissue'
group of cells that work together to perform the same function
62
what are the four main tissue types?
(in human body)
epithelial tissue
connective tissue
nervous tissue
muscle tissue
63
where may you find squamous epithelium?
lining surface of blood vessels
forms wall for capillaries and alveoli
64
what do cuboidal and columnal cells do?
line tubes in the body
65
what is the role of ciliated epithelia?
contain goblet cells that produce mucus
form surface of tubes in gas exchange
cilia moving from side to side move substances along
66
where is compound epithelia found?
where the skin is continually scratched
67
define 'organ'
several tissues that work together to carry out a particular function
68
what is meant by bacterial cell walls being 'hypertonic' to the medium around them?
water moves in by osmosis
cell wall prevents cell from swelling and bursting
69
describe the structure of peptidoglycan
many chains
peptide crosslinkages
net like structure
70
what makes up all bacterial cell walls?
peptidoglycan
71
what does a slime capsule/layer do?
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
what may the slime capsule be made from?
starch/glycolipid/protein/gelatin
73
what are pili?
protein projections from cell surface
74
what are pili used for?
attachment to host cell in sexual reproduction
make bacteria more vulnerable to viral infections - bacteriophage can use pili as an entrance point
75
what is the flagella used for in bacteria cells?
a flagella is present so that a bacteria can move itself (using rapid rotations)
76
bacteria have no mitochondria, so what is used as the respiratory site?
cell membrane
77
what is the nucleoid?
area in bacterial cell where tangled DNA is found
78
how can bacterial cell walls be identified?
gram staining
79
why is gram staining effective?
different types of bacteria are vulnerable to different types of antibiotics
80
describe the cell walls of gram POSITIVE bacteria
think layer of peptidoglycan - containing teichoic acid within net like structure
81
explain the testing of gram positive bacteria
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
describe the structure of gram NEGATIVE bacteria cell walls
thin layer of peptidoglycan
no teichoic acid
outer membrane is made from lipopolysaccharides
83
explain the testing process for gram NEGATIVE bacteria
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
why is it important for doctors to know if a bacteria is gram positive or gram negative?
this determines which antibiotic is given
85
what do beta-lactam antibiotics do?
which type of bacteria would this be most effective against?
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
explain what glycopeptide antibiotics do and what type of bacteria they are effective against
glycopeptide antibiotics are large molecules
effective against gram-positive
not effective against gram-negative because they can't penetrate the outer membrane
87
explain how polypeptide antibiotics work and against which type of bacteria
very effective against gram-negative bacteria because they interact with the phospholipids on outer membrane
88
what shape are cocci bacteria?
spherical
89
what shape are bacilli bacteria?
rod shaped
90
what shape are spirilla bacteria?
twisted
91
what shape are vibrios bacteria?
comma shaped
92
describe what obligate aerobes are
obligate aerobes are bacteria that need oxygen (for respiration)
93
describe what facultative aerobes are
bacteria that use oxygen if available but can also survive without
94
describe what obligate anaerobes are
bacteria that only respire in the absence of oxygen
(die in the presence of oxygen)
95
what is a viruses capsid (protein coat) made from?
what is the adv of it using repeating units?
repeating protein units called capsomeres.
using repeating units minimises the amount of genetic material needed to code for the capsid
96
some viruses have a lipid envelope.
what is the adv/disadv of this?
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
how do viruses attach to their host cells?
what do these do?
using VAPs (virus attachment particles)
the VAPs target the proteins in the host cell
98
describe how a DNA virus works
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
Give examples of DNA viruses
small pox
adenovirus (common cold)
bacteriophages (lambda phage)
100
describe how a RNA virus works
explain the difference between positive and negative ssRNA- give examples of viruses caused by each
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
explain how RNA retroviruses work
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
what are bacteriophages?
viruses that attack bacteria
103
how do bacteriophages infect?
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
when DNA viruses enter a cell, they are non-virulent. what is meant by this?
non-virulent means they are non-disease causing when they first get into the cell
105
what occurs in the lysogenic pathway?
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
what is meant by lysogeny?
when virus is part of reproducing cells but is not causing an affect yet. said to be 'latent'
107
what is the lytic pathway?
process of replicating and killing cells
108
describe what happens when viruses enter host cells and viral genetic material can be replicated independently.
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
what may happen when a host cell is damaged? (regarding what type of pathway it is on?)
when a host cell is damaged, may be activated from lysogenic to lytic. this is because the amount of repressor proteins decreases
110
describe how positive ssRNA viruses replicate themselves
ssRNA contain single strand of RNA
used as mRNA for translation into proteins at ribosomes
111
describe how negative ssRNA viruses replicate themselves
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
explain how RNA retroviruses are replicated
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
how can foot and mouth disease spread?
body secretions (milk/semen)
breath of infected animals
contamination (of food/water)
114
how does ebola spread from animals to humans?
faeces, meat, blood, urine (of infected animals)
then spreads between humans through blood, contaminated surfaces (eg bedding) ,faeces, fluids
115
what do antiviral treatments aim to do?
antiviral treatments aim to stop viral replication
116
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
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
what are the symptoms of ebola?
fever and internal bleeding
118
explain the difference between an epidemic and a pandemic.
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
suggests ways that disease can be controlled
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
state the stages in drug development
early phase research
pre clinical testing
clinical trials
regulatory review
scale up to manufacturing
post market surveillance
121
give suggestions of possible things to consider when evaluating whether a drug should be fast tracked
effectiveness of other treatments
effectiveness of normal disease control methods
122
suggests criticisms of using an untested drug
side effects
seen as unethical
informed consent- dying people want it but relatives may then blame it for the death
123
how could antibiotic treatment be used to identify if a bacterium is gram positive or gram negative?
if antibiotic worked , gram positive
gram positive has a cell wall with more peptidoglycan , this is a target site for the antibiotic
124
What does the cell cycle produce?
two genetically identical daughter cells
125
What are the three stages of the cell cycle and what do each of these consist of?
interphase - G1, S, G2
mitosis - P M A T
cytokinesis
126
interphase consists of G1, S , G2 phase.
What occurs in each of these stages?
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
describe the stages of mitosis
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
purpose of mitosis
growth and repair
129
examples of asexual reproduction
budding/binary fission/vegetative propagation
130
what happens in cytokinesis?
Cell membrane pulled in by cytoskeleton
Creates furrow which deepens
Cytoplasm is split, forming two identical daughter cells
131
stages of meisosis
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
name and explain the features of sperm
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
name and explain the features of an egg
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
explain how stopping the proper formation of spindle fibres can stop cells dividing.
fibres are unable to contract
chromosomes can not be pulled to opposite ends of cell
new cells can not be made
135
in which stage of the cell cycle does DNA replication occur?
interphase
136
explain how male gametes are formed in plants
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
explain how female gametes are formed in plants
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
explain this type of asexual reproduction:
sporulation
Mitosis and production of asexual spores
ferns/mosses/fungi
139
explain this type of asexual reproduction:
regeneration
Replacing parts of the body which have been lost
140
explain this type of asexual reproduction:
fragmentation
Reproduce themselves asexually from fragments of their own body
141
explain this type of asexual reproduction:
budding
Outgrowth from parental organism, which produces identical but smaller organisms
142
explain this type of asexual reproduction:
vegetative propagation
Plant forms a structure which develops into a totally differntiated new plant
Identical to parent but eventually becomes independent
bulbs/running
143
what is a feature of all RNA viruses ?
surrounded by a protein coat
144
name some RNA viruses
ebola
TMV
145
do bacteria , viruses or both have nucleic acid?
both
146
do bacteria , viruses or both have cytoplasm?
bacteria only
147
do bacteria , viruses or both have protein capsid?
virus only
148
How does a DNA virus work?
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
name a DNA virus
lambda phage
150
What is the difference between positive ss RNA virus and negative ss RNA virus?
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
give an example of an RNA retrovirus
HIV
152
describe how an RNA retrovirus works
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
What does HIV target?
CD4 t lymphocytes (host cell)
causes immune response - T-killer now kill T-lymphocytes as they have the virus in it
154
What bacteria is Tb caused by?
Mycrobacterium tuberculosis
