Lesson 3 Flashcards
(109 cards)
1
Q
What is the central dogma of biology?
A
DNA –> mRNA –> Proteins
2
Q
How do viruses ‘disobey’ the central dogma of biology?
A
- Reverse translation is possible for some viruses
- RNA duplication is possible for some viruses
3
Q
What are some characteristics of viruses?
A
- cannot grow with nutrients only, need to infect host to grow
- do not have necessary enzymes to replicate
-genome is double stranded DNA/RNA or single stranded DNA/RNA
-It needs to produce all the proteins in the virus particle and enzymes to reproduce its genome
4
Q
What genes could be missing in viral genome?
A
Genes that code for ribosomal RNA and ribosomal proteins for protein synthesis, the aminoacyl-tRNA transferases
5
Q
What genes must viruses have?
A
they must have genes coding for proteins that are necessary but not found in their host.
If it has a single-strand RNA genome, it must have polymerases able to reproduce the RNA genome.
6
Q
No living organism has polymerases that can copy (transcribe) the RNA into RNA and/or DNA.
True or false
A
True
7
Q
RNA viruses must provide proteins to produce an RNA genome. The hosts, all with DNA genomes, do not have this set of proteins.
True or False
A
True
8
Q
What are the two strategies of viral genome replication?
A
- Making the mRNA for viral-specific proteins
- Making the genome
9
Q
What enzyme is needed to make DNA out of RNA?
A
Reverse transcriptase
+ssRNA –> -ssDNA –> dsDNA –> mRNA
10
Q
How does viral +ssRNA make mRNA?
A
1.+ssRNA –> -ssDNA –> dsDNA –> mRNA
2. +ssRNA –> dsRNA –> mRNA
11
Q
How does ssDNA make mRNA?
A
+ssDNA/-ssDNA –> dsDNA –> mRNA
12
Q
Give a brief description of tobacco mosaic virus?
A
RNA genome: 6396 nucleotides
4 genes only.
it must contain the gene to
produce the capsid protein, and other genes to facilitate the reproduction of its RNA genome
13
Q
What kind of genetic material does TMV possess? How does it replicate?
A
+ssRNA
It makes a complementary
-ssRNA. The -ssRNA is used to make copies of the viral strand
(TMV must have machinery to make single strand RNA from signle strand RNA.)
14
Q
What is virus specificty?
A
Generally, a virus may infect certain animals but not others.
This is due to the slight difference in the corresponding receptors
in the animals are slightly different.
The virus can “jump” species because of mutations in their own entry protein so that it can now bind to the receptor of a new species.
15
Q
Name some viruses.
A
Hepatitis B
Smallpox
AIDS
Ebola
Influenza
SARS
16
Q
Name some factors that affect the incidence of various diseases?
A
- Population
- Urbanization
- Change in sanitation habits
- Change in lifestyle
- Ease of travel and migration
- Aging populations
- Climate change
17
Q
What are the two types of immune reponses?
A
Primary response and Secondary response.
Secondary is more rapid and robust
18
Q
Name some haptens
A
Urishiol
Aniline
4-aminobenzoic acid
19
Q
Can haptens induce immune reponse on their own?
A
No, haptens need to be
coupled to a larger (protein) molecule to elicit an immune response
20
Q
State the difference between antigen and immunogen
A
Antigens are moieties that can be recognized by antibodies,
immunogens are molecules that can elicit an immune response
21
Q
What is an epitope?
A
the site on the antigen recognized by an antibody is the “epitope”
22
Q
Name 2 enzymes that can digest antibodies
A
Papain and Pepsin
23
Q
Name the products produced by antibody digestion of papain
A
Fab, which remains antigen binding activity
Fc, crystallizable
24
Q
Name the products produced by antibody digestion of pepsin
A
F(ab’)2, with antigen binding activity, about twice the size of Fab
pFc’, no function and no crystal
25
What type of protease is papain?
cysteine protease, with cysteine at the active site
26
What is the specificity of papain?
hydrophobic-(Arg/Lys)-(not Val)
27
What type of protease in pepsin?
Aspartic acid at the active site.
Active in acidic pH (2.5)
Inactive at neutral pH (>6.5)
28
What is the specificity of pepsin?
hydrophobic-aromatic
29
What can be used to denature proteins?
Urea, it disrupts the hydrogen bonds of alpha-helices and beta-sheets of proteins
30
Name 2 reducing agents that can be used to break disulphide bonds.
Which is better?
beta-mercaptoethanol and dithiothreitol.
Dithiothreitol because the second step involves an intramolecular reaction
31
What are the 2 regions called in variable region of light and heavy chains?
Framework region x3
Hypervariable region x3 (Complementarity determining region CDR)
32
33
For the light chains, what is the difference in their secondary protein structure in variable region and constant region
Variable region: 9 beta strand (2 beta sheets with a disulphide bond)
Constant region: 7 beta strands (2 beta sheets with a disulphide bond)
34
What multimers can be formed by the interaction of dimeric haptens and antibody? Why?
dimer, trimer and tetramer.
Because of the flexibility of the hinge region
35
What interactive forces are present between an antibody and an antigen?
1. Electrostatic forces (opposite charges)
2. Hydrogen bonds
3. Van Der Waals forces (fluctuations in electron clouds)
4. hydrophobic forces
36
What are the 3 zones of antigen-antibody precipitation?
1. Zone of antibody excess
2. Zone of equivalence (ppt formed)
3. Zone of antigen excess
37
What technique did Orjan Ouchterlony discover?
Agar plate with wells for antigens and antibodies
Diffusion would allow a natural gradient to form from the wells. Precipitation lines will form when the concentrations reach “equivalence”.
38
For type A blood, what is added on the red blood cells?
N-acetyl galactosamine
39
For type B blood, what is added on red blood cells?
galactose
40
Which blood group is the universal donor?
type O
41
What are the major targets of the immune system
1. Pathogens
-bacteria
-virus
-parasites (protozoan,
animal)
-fungi
-plants through bacteria
or viral residents or
toxins
2. Cancer cells
3. Immune complexes
42
What are some common fungal complexes?
1. Oral Candidiasis
2. Athlete's foot
3. Aspergillioses
43
Name some common parasite infection
Ameobiasis (protozoan),
Malaria (unicellular parasite protist),
Tapeworm (animal)
44
What is ameobiasis?
Ameobiasis (protozoan), caused by amoeba trough ingestion. Abdominal pain, bloody diarrhoea.
Can be very severe if they digest though the intestinal tract and wander to other
sites in the body
45
How is malaria spread?
Malaria (瘧疾) (unicellular parasite - protist) transmitted through mosquito bites. Complex life cycle but an obligatory stage is by entry
into an erythrocyte.
46
What are the routes of entries of pathogens?
1. Mouth and respiratory tract
2. gastrointestinal tract
3. reproductive tract (STDs)
4. Skin (external epithelia)
47
Why are mucosal surfaces important for pathogens when they enter the body?
Because they are the exposed surfaces that are necessary for nutrition acquisition
48
What pathogens enter through the respiratory tract?
Influenza – virus
Measles – virus
Anthrax – bacterial spore
49
What pathogens enter through the gastrointestinal tract?
Food poisoning – Salmonella (bacteria)
Cholera – bacteria
Hepatitis B – virus
50
What pathogens enter through the reproductive tract?
AIDS – HIV virus
Gonorrhea – bacteria
Syphilis – bacteria
51
What pathogens enter through the skin?
External surface:
Athlete's foot -- fungus
Wounds and abrasions:
Tetanus - bacterial (toxin)
Insect bites:
Malaria -- protozoan (mosquito)
Yellow fever -- virus (mosquito)
Lyme disease -- bacteria (tick - insect)
52
Name some pathogens that are spread through insect bites
Malaria – protozoan (mosquito)
Yellow fever – virus (mosquito)
Lyme disease – bacteria (tick – insect)
53
Name opportunistic pathogens that attack immuno-compromised individuals
Candidiasis – fungus (intestine)
Pneumonia – fungus (lung)
54
What are the infections sites of pathogens?
1.extracellular (epithelial surfaces and interstitial spaces, blood, lymph)
2. Intracellular (cytoplasmic and vesicular)
55
What makes up the first line of defense?
Skin, gut, lungs, facial cavities
56
What are the mechanical barriers in first line of defense?
Layers of dead skin, tight junctions between cells and epithelial cells
Skin and gut: constant fluid flow
Lungs: Mucus
Facial cavities: tears
57
What are the chemical barriers in first line of defense?
Defensins
Skin: fatty acids
Gut: Acidic pH (pepsin)
Lungs: surfactant
Facial cavities: Enzymes (lysozyme)
58
Apart from mechanical and chemical barriers in the first line of defense, what else is present to serve as a defense mechanism?
Microbiological -- normal microbiota (good bacteria crowd out the pathogens)
59
What are defensins?
Defensins are amphipathic small peptides that disrupt cell membranes of microbes. The α-defensins are produced in neutrophils, and β-defensins in the epithelial cells in the gut.
60
How do defensins work?
By disrupting the cell membranes of microbes
61
What are the two types of defensins and where are they produced?
The α-defensins are produced in neutrophils, and β-defensins in the epithelial cells in the gut.
62
What is the function of surfactants lining the alveoli?
-lower surface tension
-prevent collapse of lung (atelectasis) during breathing
-promote ingestion of microbes by microphages
63
What are the four major tasks of the immune system?
1. Immunological recognition
2. Immune effector functions
3. immune regulation
4. immunological memory
64
In innate immune response, what are the molecules that recognize pathogen-associated molecular patterns (PAMPs) called?
Pattern recognition receptors
65
What are the major molecules in the adaptive immune response?
Antibodies and t cell receptors
66
How many leukocytes in blood?
8 million per mL
67
What capability must a stem cell possess?
must be able to self renew
68
Name the four types of granulocytes
Neutraphil
Eosinophil
Basophil
Mast cell
69
How do granulocytes and lymphocytes compare to monocytes in terms of their structure?
The monocytes have a more-or-less “compact” nucleus.
It has relatively less granules than the granulocytes, and
has more cytoplasm than the lymphocytes.
70
Heme is toxic when released into blood.
In what form is it carried in the plasma?
Bilirubin
Heme --> biliverdin --> bilirubin
71
How many red blood cells per mL of blood?
5 billion (5 x 10 ^9)
72
What process does erythroblast go through in order to differentiate into a RBC?
chromatin condensation.
nucleus is pinched off eventually
73
What is a reticulocyte?
Reticulocyte is the immature red blood cell.
It has no nucleus but with residual ribosomes and RNA
74
Name some animals with decreasing size of erythrocyte
Human > mouse > sheep > goat
75
Name animals that have nucleus in their red blood cells
Birds and Fish
76
Name the stages though which the maturation of mammalian erythrocyte occurs
Pre-erythroblast, erythroblast, RBC
77
Why is megakaryocyte named that way?
Mega: large
Karyo: Nucleus
Megakaryocyte --> cell with large nucleus
78
How is megakaryocyte 'polyploidy'?
At the megakaryocyte stage, chromosome replication
continues and growth in cell volume but no cell division.
They become “polyploidy”, at the 4N, 8N, and 16N.
For human, it can be up to 64N, and mouse, 256N.
79
Do megakaryocytes release into the blood?
No
Platelets start to pinch off from the megakaryocyte and are released into the blood stream. The megakaryoctes stay in residence in the bone marrow.
80
Name the stages through which megakaryocytes mature in the bone marrow?
Hemocytoblast --> megakaryoblast --> promegakaryoblast --> megakaryocyte --> platelets
81
What are some physical characteristics of neutrophil?
- 2-5 lobes of nucleus
-No rough endoplasmic reticulum (RER), small Golgi, and low numbers of mitochondria and ribosomes
-200 granules
82
How long do neutraphils survive for?
~10 (2-90) hrs in the blood
83
What is leukocyte adhesion deficiency?
neutrophils cannot move into tissues. They
suffer from recurrent infections of all kinds
84
Why are neutrophils needed?
They are needed to migrate into tissue to combat infectious pathogens.
85
What is the sequence of extravastation of neutraphils?
1. E-selectin on endothelial cells adhesion to s-lex on neutraphil
2. IL-8 activate β2 integrins on the neutrophil surface
3. TNF-α induce endothelial cells to express ICAM-1
4. β2 integrins bind to ICAM-1
5. rearrangement of actin cytoskeleton
6. CD31 on endothelial cell interact with CD31 on neutraphil --> allow diapedesis
7. metallo-proteases digest basement membrane
8. IL 8 concentraton gradient created
9. gradient sensed by IL-8 receptors on neutrophil
10. β1 integrins on neutraphil allow crawling
86
What are cytokines?
proteins made by a cell that affect the behaviour of another cell.
87
What are interleukins?
cytokines made by lymphocytes.
88
What are chemokines?
cytokines that stimulate the migration of cells.
89
What is extracellular matrix?
a network of multidomain macromolecules in the
tissues; fibronectins, collagens, and fribillins are components of the
extracellular matrix
90
What is cytoskeleton?
Cytoskeleton: the structure that defines the shape of the cells, mostly mediated by the intracellular filaments: actin, microtubules, and intermediate filaments such as keratin in skin cells.
91
What is LAD-1 cause by?
due to the disfunction of the
β2 integrins. Cells cannot form the firm adhesion before diapedesis. Neutraphils remain in blood
Another mutation in LAD-1 was found to be super-adhesive, cells get stuck ....
92
What is LAD-2 caused by?
LAD-2 is due to the defect in the glycosylation of proteins, thus the cells cannot roll to slow down.
93
What is LAD-3 is caused by?
LAD-3 is due to the mutation of kindlin, an intracelllular protein responsible to activate the β2 integrins
94
Where do monocytes develop into 'resident macrophages'?
Monoctyes migrate constantly from blood into tissues and develop into “resident macrophages”, where they would stay for a much longer period than the
neutrophils, up to several months.
95
What is the function of macrophages?
Phagocytosis/ ingestion of microbes
96
What are the three major antigen-presenting cells (to T cells)?
Macrophages, dendritic cell and the B lymphocytes
97
What is the main function of dendritic cells?
Present antigens to T cells.
They encounter antigens in tissue, then migrate to lymphoid tissues (lymph
nodes) through the lymphatics to present the antigens to T-helper cells.
98
How do natural killer cells differ from B and T cells?
They do not express surface antibodies like the B cells, nor T-cell receptors like the T
cells.
NK cells are larger than the lymphocytes, and they have granules with cytotoxic molecules.
99
NK cells can kill virus infected cells, and some cancer cells without the need
of specific immune stimulation.
True or false
True
100
What are the enzymes involved in the following reaction?
Heme --> biliverdin --> biliirubin
heme oxygenase-1 for heme --> biliverdin
Biliverdin reductase for biliverdin --> bilirubin
101
What are the cytokines made by lymphocytes called?
interleukins
102
What are the 4 main steps through which extravastation of neutrophils occurs?
1. Rolling adhesion
2. Tight binding
3. Diapedesis
4. Migration
103
What is the characteristic of dendritic cells?
--> do not have extensive membrane systems including granular vesicles.
--> myeloid lineage
--> immature in blood and activated on encounter with “presentable” antigens in tissues
104
Contrast macrophages and dendritic cells given that both are antigen-presenting cells
-macrophages are important in the ingestion of pathogens as well as cell debris in the body, DC is more important in their capacity to present antigens
- dendritic cells do not have a fixed residency
- no extensive membrane system
105
What is the function of macrophages in the spleen?
The macrophage in the red pulp is responsible for the removal of senescent RBSs
106
What are the three types of macrophages in splee?
1. marginal zone macrophages
2. marginal metallophilic macrophages
3. red pulp macrophages
107
What happens to dendritic cells after they have encountered antigens?
They encounter antigens in tissue, then migrate to lymphoid tissues (lymph
nodes) through the lymphatics to present the antigens to T-helper cells.
108
What do granules contain?
perforins and granzymes
109
What is the function of granzymes?
Granzymes induce target cells to undergo apoptosis or “programmed cell death”.
