cell cycle and the immune response Flashcards
1
Q
what does the cell cycle consist of?
A
-a period of growth and DNA replication (interphase)
-a period of cell division (mitosis)
2
Q
describe the stages of interphase
A
G1= cell grows
-increase in num of organelles
-proteins made
-ATP synthesised
S= synthesis of DNA (replication)
G2= further cell growth
-proteins made
-ATP synthesised
3
Q
what are the stages of mitosis?
A
prophase
metaphase
anaphase
telophase
4
Q
what are homologous chromosomes?
A
pairs of chromosomes that contain the same genes in the same loci not necessarily same alleles
-one maternal
-one paternal
-same size,shape,
-centromere same shape
5
Q
what occurs during interphase?
A
-DNA replicates
-ATP synthesised
-organelles synthesised including centrioles
-proteins synthesised
6
Q
in interphase, why is ATP synthesised?
A
to provide energy for cellular respiration
7
Q
why are centrioles synthesised?
A
-to carry out cellular functions
-centrioles take part in separation of chromosomes
8
Q
if DNA not copied accurately, what may happen?
A
mutations may occur
daughter cells wont receive identical genetic material
9
Q
describe the process of semi conservative replication of DNA
A
- double helix untwisted
- DNA helicase breaks H bonds
- both strands act as a template
- Free DNA nucleotides bind to the bases on the template strands using complementary base pairing rule
- adenine + thymine, cytosine +guacine held by H bonds
- DNA polymerase joins sugar-phosphate backbone forming phosphodiester bonds
- condensation reaction
- one new, one old strand
10
Q
what is mitosis important for?
A
-to produce genetically identical daughter cells
-asexual reproduction
-growth
-repair
-replacement e.g. skin + red blood cells
11
Q
define mitosis
A
nuclear division
12
Q
what happens in prophase?
A
-replicated chromosomes shorten and thicken (supercoil)
-each chromsome consists of a pair of sister chromatids
-nucelar envelope breaks down and disappears
-centriole divides into 2
-each daughter centriole moves to opp poles of cell to form a spindle
13
Q
whats a spindle?
A
protein threads
14
Q
what happens in metaphase?
A
-replicated chromosomes line up down equator
-each chromosome (pair of chromatid) is attatched to a diff spindle fibre by its centromere
15
Q
what happens during anaphase?
A
-replicas of each chromosomes are pulled apart from each other towards opposite poles of the cell
-identical sister chromatids are pulled to different poles by shortening of spindle fibres
-centromeres divide
16
Q
what happens during telophase?
A
-two new nuclei are formed
-sister chromatids reach poles and are now chromosomes
-spindle breaks down and disappears
-chromosomes uncoil cant be seen in a light microscope any more
17
Q
what is cytokenesis?
A
the division of the cytoplasm
occurs between telophase and interphase
18
Q
describe cytokinesis in animal cells
A
-microtubules form a ‘draw string’ just inside the membrane
-fuses as it is pinched
-forms a cleavage cell, two genetically identical daughter cells are produced
19
Q
describe cytokinesis in plant cells
A
-microtubules direct vesicles to the middle of the cell to form cell plate
-which forms a new cell wall
-new cell surface membrane is made on either side to enclose the two cells
20
Q
define mutation
A
a change in base sequences of DNA
21
Q
when does a tumour become cancerous?
A
if it changes from benign to malignant
22
Q
what does the treatment of cancer involve?
A
killing dividing cells by blocking part of the cell cycle
the cell cycle is distrupted
23
Q
what enzyme controls cell division?
A
CRIPR
24
Q
limitations in cancer treatment?
A
-does not distinguish tumour cells from normal cells
-normal body cells that divide rapidly (hair) are vulnerable
25
how do drugs that treat cancer disrupt the cell cycle?
-preventing DNA replicating, severe damage to DNA, the cell would kill itself (apoptosis)
-inhibiting the metaphase stage of mitosis by interfering with spindle formation
-preventing the synthesis of enzymes (RNA, Polymerase) needed for DNA replication in S stage
26
what is a tumour?
-a large mass of abnormal cells/tissue
-undergoing uncontrolled cell division/mitosis
27
what are antigens?
foreign proteins which stimulate an immune response and are targets for the response
28
why can antibody molecules bind specifically to antigens?
because their shapes are complementaryh
29
how do abnormal body cells trigger an immune responce?
cancerous or pathogen infected cells have abnormal antigens on their surface
30
our body's ability to identify foreign antigens allows our immune system to respond to:
-pathogens
-abnormal body cells
-toxins
-cells from other individuals
31
define a pathogen
a disease causing agent that stimulates an immune response
32
give 2 non-specific defence mechanisms
-primary defence mechanisms
-phagocytosis
33
give 2 specific defence mechanisms
-cell mediated response (T lymphocytes)
-humoral response (B lymphocytes)
34
whats the difference between the non-specific and non-specific?
non-specific= response is immediate and the same for all pathogens
specific= response is slower and specific to each pathogen
35
what makes up the primary response?
-vagina=lactic acid
-skin=physical barrier. harmless bacteria= commensal flora that competes with pathogenic bacteria
-mucous membranes=respiratory passages
ciliated cells waft mucus to top of trachea, sticky mucous traps pathogens
-eyes= tears contain antibodies and lysozymes
-earwax= lysozymes, wax traps pathogens
36
what are phagocytes?
cells that engulf and digest pathogens and other non-self material e.g. dust particles in lungs
37
where are phagocytes made?
bone marrow
38
what are the 2 types of phagocytes?
neutrophils and macrophages
39
differences between neutrophils and macrophages
-neutrophils are short lived whereas macrophages are long lived as survive after engulfing bacteria
-neutrophils are made in the bone marrow and reside in blood and tissue fluid whereas macrophages develop in lymph nodes
-neutrophils initiate the immediate response whereas macrophages are involved in the specific immune response
40
what are the steps involving phagocytosis?
1-detection of antigens by phagocyte
2-engulfing of the pathogen = phagosome
3-fusion of the lysosome with phagosome = phagolysosome
4- release of hydrolytic enzymes into the phagosome
5-presenting the antigens on the cell membrane
41
why are T and B lymphocytes considered apart of the specific immune response?
they target specific antigens on the surface of the pathogen
42
what does the specific immune response provide?
long term immunity
43
differences between T and B lymphocytes (T and B cells)
-T-cell= mediated response whereas B cells are involved in the humoral response
-T-cells directly target pathogens whereas B cells produce antibodies
-T cells mature in the thymus whereas B cells mature in bone marrow and migrate to lymphnodes
44
how does the phagocyte find the pathogen?
antibodies attract phagocytes. Antibodies produced by the body can recognise and bind to pathogens. These antibodies act as a chemical beacon which attracts phagocytes to the pathogen.
Chemicals attract phagocytes.
The pathogen releases chemicals, which attract pathogens to the site.
Both processes are examples of chemotaxis
45
How does skin play a role in the innate immune response?
Skin acts as a physical barrier to pathogens, preventing them from entering the body. It is also covered in antimicrobial substances that help to kill pathogens on contact.
eg commensal flora
46
why do T lymphocytes recognise pathogens as non-self?
1. a macrophage has engulfed and hydrolysed the pathogen and presented the pathogens antigens on the cell surface membrane
2. a T-lymphocyte with specific T cell receptors will bind to compleentary antigens presented. this activates T cells to undergo clonal expansion. these differentiate into either T helper cellls or cytotoxic T cells
47
what do T helper cells activate?
and how?
-phagocytes
-T cytotoxic cells
-B cells
by releasing chemical signals called cytokines
48
how does the immune system respond to antigens?
-break down of foreign cells by lysozymes
-phagocytosis of foreign cells
-production of antibodies
49
what is the role of cytotoxic cells?
-recognise antigens on pathogens
-the cell receptor protein will bind to these antigens
-secrete perforin protein that make holes in the cell surface membrane
-holes mean the cell surface membrane becomes freely permeable to all substances and the cell dies
50
what are the steps in the cell mediated response?
after phagocytosis
2. clonal selection= specific T cells with complementary receptors selected
3. clonal expansion= mitosis= specific T cell cloned
4. differentiaton
5.into cytotoxic T cells and Helper T cells
TH=activate B cells
Tc = kill infected cells, toxins=perforins
51
what are the steps in the humoral response?
1. the B cells are activated by T helper cells by cytokines
2.clonal selection=specific B cells with complementary antibodies are selected
3.clonal expansion= specific B cells are cloned by mitosis
4. differentiation
5.plasma B cells = secrete antibodies specific to pathogens antigen
memory B cells = remain in blood
immunological memory
provide a faster response
52
why is the primary immune response much slower?
-when a pathogen it takes a few days to produce plasma b cells, T helper and cytotoxic T cells because there are few B and T cells with correct specificity for the particular antigens on the pathogen.
-takes time for clonal selection and expansion
53
what is the latent period?
where no antibodies are present
54
why is the secondary immune response faster?
-reinvasion of pathogen
-memory B and T cells are rapidly activated because with many memory cells of the correct specificity
-takes little time for one or more to encounter the antigen
-b memory cells divide rapidly to produce lots of plasma cells
-results in more antibodies produced at a faster rate
55
what is the structure of an antibody?
-4 polypeptide chains= 2 light, 2 heavy
-each has a specific binding site complementary to the antigen
- 2 variable region=diff specific binding site for each different shaped antigen
- 1 constant region=same in all antibodies- binds to phagocytes
56
how are antibodies used in treatment of cancer?
-antibodies recognise specific antigens only found on one specific cell type
-tag a drug to antibody and only cancer cells will be exposed to the drug and die
57
whats the hinge region for?
flexibility
58
what 3 ways are antibodies able to combat pathogens?
1.agglutination
2.neutralisation
3.act as markers that attract phagocytes. then engulf pathogen
59
what is agglutination?advantage?
forming antibody-antigen complexes the pathogens are held together in large clumps
phagocytes can more easily engulf huge quantities of pathogens which are immobilised by agglutination
60
what are monoclonal antibodies?
-antibodies produced from a single group of genetically identical B plasma cells.
-they are identical and specific to one antigen
-can be produced in the laboratory for treating illness and medical diagnosis
61
what do cancer cells have on their surface that arent on normal body cells?
antigens called tumour markers
62
benefits of magic bullets?
-can be used in small dosages
-so cheaper and
-reduces possible side effects
63
what are some ethical issues on antibodies?
-transgenic animals
-side effects of treatments
64
explain why structure and function of antibodies are similar to enzymes?
1. both have binding sites
2. variable region of antibody specific structure, active site of enzyme has a specific structure
3. antibody binds w/ a specific antigen, enzyme binds w/ specific substrate
4. antibody form antibody-antigen complex, enzyme forms enzyme-substrate complex
65
what anti-cancer drug is used to treat breast cancer?
herceptin
66
what are uses of monoclonal antibodies?
-medical diagnosis
-targeted medication
67
how do anti-cancer drugs work?
monoclonal antibody bind to antigen on cancer cell called a tumour marker
means the drug will only accumulate in the body where there are cancer cells
68
whats the purpose of a control region on pregnancy test?
prevent a negative result
shows test is working and antibody has moved up strip
69
what are the three zones on a pregnancy test?
-reaction zone
-test zone
-control zone
70
how do pregnancy tests work?
Pregnancy testing sticks contain monoclonal antibody molecules that are specific to a hormone produced during pregnancy (that therefore becomes present in the mother's urine)
This hormone is human chorionic gonadotropin (hCG), which is secreted by the early embryo after it has implanted in the uterus
The antibodies in the testing sticks all originate from a single clone of B lymphocyte cells that all produce the same antibody specific to hCG
This minimises the chances of false test results
71
what happens in the first zone of a pregnancy test?
- the mobile monoclonal antibodies that have combined with hCG bind to a layer of fixed antibodies
-this gived a coloured line in first window indicting hCG is present = positive
72
what is an immobilised antibody?
antibody that has been fixed in place
73
what happens in the second zone of a pregnancy test?
-antibodies that have not bound to hCG bind to a second layer of fixed antibodies
-a coloured line here shows that antibodies have been mobilised and have moved up the sampler
-this is important to indicate if there is no line in the first window a negative result is correct
74
for pregnancy, what indicates a positive result? a negative?
2 blue lines
1 blue line is negative
75
how many days after conception, can hCG be found?
6 days
76
when is hCG secreted?
when a human embryo implants into the uterine lining
77
what does ELISA stand for?
enzyme-linked immunosorbant assay
78
what does the ELISA test uses?
allows you to see if a patient has any antibodies to a certain antigen
can be used for medical diagnosis to test for pathogenic infection, allergies
79
in ELISA test how can the result be quantified?
by looking at colour intensity
80
whats the difference between the indirect and direct ELISA?
-direct = uses one antibody complementary to the antigen
-indirect = uses two different antibodies
81
describe the steps in Direct ELISA
1.collect a sample blood/saliva from a patient = this will contain the antigen
2. add complementary antibody with enzyme attached
3. if antigen present antibody binds
4. wash to remove any unbound antibodies
5. add substrate complementary to active site of enzyme
6. coloured product formed if present
82
describe the test for the indirect ELISA
1. HIV antigen bound to bottom of well
2. plasma sample added. any antibodies specific to antigen will bind
3. wash to remove unbound
4. enzyme attached secondary antibody added. this will bind to primary antibody
5. wash to remove unbound 2nd antibodies
6. substrate added and any colour change indicates a positive result
83
define active immunity
immune system produces its own antibodies after being stimulated by an antigen
84
define passive immunity
introduction of antibodies into individuals from an outside source
immune system does not produce any unknown antibodies
85
whats the limitation with passive immunity?
no B-plasma cells are activated so no long term immunity as no B -memory cells
86
give examples of natural and artificial active immunity
-natural= individual infected with disease under normal circumstance. body produces own antibodies
-artificial = involves inducing an immune response eg vaccination
87
give examples of natural and artificial passive immunity
-natural = antibodies from mother passed through placenta or breast milk
-artificial = injected with antibodies eg tetanus
88
differences between active and passive immunity
-requires exposure to antigen whereas passive does not
-active = immune response takes a while whereas passive provides immediate protection
-in active immunity, memory cells are produced whereas non are produced in passive
-active immunity provides long term protection whereas passive immunity is short term protection as antibodies get broken down
89
define vaccination
deliberate exposure to harmless antigenic material to activate then immune response and antibodies and memory B cells provide immunity
90
what may be the need for multiple vaccinations?
high antigenic variability
91
why even with successful vaccination, it can be difficult to eradicate a disease?
-fails to induce immunity in certain individuals
-pathogen may have high antigenic variability so vaccine no longer effective
-varieties of a particular pathogen
-individuals may have objections to vaccinations for religious, ethical or medical reasons
92
what percentage of the population needs to be vaccinated for herd immunity?
90%
93
what are some ethical issues with vaccines?
-tested on animals
-testing on humans is too risky . who should take part in trials?
-side effects , long term harm?
-to be fully effected whole population needs to be vaccinated. should it be compulsory?
94
ethical issues with monoclonal antibodies?
-production involves mice = tumour cells directly induced to have cancerous cells
-have been some deaths associated with multiple sclerosis so still risks
95
give 3 vaccine ethical questions
1. should NHS provide vaccines that are expensive?
2. should vaccination be compulsory in school children
3. how can vaccines be prioritised when stocks are low?
96
what does HIV use to replicate?
-host enzymes
-ribosomes
97
what 2 enzymes are in HIV capsid?
1. reverse transcriptase
2. integrase
98
what is HIV?
human immunodeficiency virus that effects the human immune system
99
what are the 2 types of attachment proteins on HIV viruses?
CD8
CD4
100
what is AIDS?
-aquired immune deficiancy syndrome
-immune system deteriorates and eventually fails
-makes someone with AIDS more vulnerable to other opportuistic infections like pneumonia and TB
101
when does HIV develop to AIDS?
when helper T cells reach a critically low level
102
what happens in the latency period?
the virus remains dormant in the cells
no symptoms, can be 10yrs
103
what does HIV target?
infect and eventually kill Helper T cells
104
what are the steps involved in replication of HIV?
1. HIV binds to the T helper cell surface
2. HIV injects capsid into the T helper cells
3. RNA, reverse transcriptase and integrase are released from capsid
4. reverse transcriptase converts single stranded RNA into double stranded DNA
5. integrase inserts DNA into the T helper cell DNA
6. the genes are expressed and HIV proteins are synthesised to make viral proteins
7. new HIV viruses bud off wrapping itself in the membrane envelope
105
What’s an ELISA
-Enzyme linked immunosorbent assay
- when enzymes are attached to monoclonal antibodies to help with detection of presence of a specific substance
