Week 5 Flashcards
1
Q
What are protozoa?
A
Single celled animals
2
Q
Are fungi eukaryotes or prokaryotes?
A
Eukaryotes
3
Q
What are some of the main differences between eukaryotes and prokaryotes?
A
Prokaryotes tend to be smaller
Prokaryotes are relatively simple and tend to be single celled
Prokaryotes have single circular chromosomes and rarely have introns
4
Q
What type of ribosome is found in a eukaryotic and prokaryotic cell?
A
Eukaryotic - 80s
Prokaryotic - 70s
5
Q
What type of organism may a peptidoglycan cell wall be found in?
A
Prokaryotic
6
Q
How is energy generated across the cytoplasmic membrane?
A
Electrons are released from the cytoplasm, and pass through a series of electron receptors in the membrane. This creates a positive charge and proton gradient across the membrane which can be used by ATP synthase for energy.
7
Q
Where would a nucleoid be found?
A
Prokaryotic cells
8
Q
Does the nucleoid have a nuclear membrane?
A
No
9
Q
What are the repeated sugar chains in a peptidoglycan cell wall?
A
NAM
NAG
10
Q
What cross link the sugar chains in peptidoglycan cells walls?
A
Peptide side bridges of 5 amino acids
11
Q
What organisms have multiple layers of peptidoglycan cell wall?
A
Gram +ve
12
Q
Describe the cell wall in a Gram -ve organism.
A
Relatively small peptidoglycan layer often decorated with LPS.
13
Q
What type of organism will likely have a second membrane and what purpose can this serve?
A
Gram -ve
Acts as another barrier and creates a periplasmic space where reactions can occur
14
Q
What does LPS stand for?
A
Lipopolysaccharide
15
Q
What purpose to LPS serve
A
Structural role
Immunostimulatory
Linked to sepsis and septic shock
16
Q
What purpose can flagella serve?
A
Rotary motor allowing motility
17
Q
What are the four classic growth stages of bacteria?
A
Lag phase
Exponential phase
Stationary phase
Decline phase
18
Q
What sources of nutrition are needed for prokaryotic growth?
A
C
O
H
N
Inorganic salts - P, S, K, Mg, Ca, Fe
Trace elements - Zn, Cu, Mn, Ni, Mo
Vitamins
18
Q
What temperature is ideal for psychrophiles?
A
Low
18
Q
What temperature is ideal for thermophiles?
A
High
19
Q
What temperature is ideal for mesophiles?
A
Body temp
20
Q
What are the four themes of microorganism classification?
A
Appearance
Growth requirements
Enzyme/metabolic tests
Molecular tests
21
Q
What are the common shapes seen in bacteria?
A
Cocci
Bacilli
Spiral-shaped
22
Q
What are the types of cocci structure?
A
Individual or attached - Diplococci
Division in one plain to produce chains
Division in three plains to produce clumps
23
Do cocci tend to be Gram +ve or -ve?
Gram +ve
24
What structures can bacilli be found in?
Individual
Chains
25
When do bacilli tend to be gram +ve and gram -ve?
In chains tend to be Gram +ve
In individual tend to be Gram -ve
26
Describe fusiform bacteria.
Long slender rods
27
Are curved rod bacteria gram +ve or gram -ve?
Gram -ve
28
What types of spiral-shaped bacterial can be found?
Rigid spiral
Flexible spiral
29
In a gram stain what type stains darker?
Gram +ve
30
Name an organism that does not stain well with Gram staining?
TB
31
What are aerobic bacteria?
Grow in oxygen/air
32
What are obligate aerobe bacteria?
Require oxygen in laboratory conditions
33
What are obligate anaerobe bacteria?
Killed by oxygen
34
What are facultative anaerobe bacteria?
Can tolerate oxygen but use anaerobic energy production
35
What is selective media?
Selects for the growth of specific prokaryotes
36
What is differential media?
Visible changes in colonies facilitating identification due to incorporation of chemicals in media
37
What characteristics may be seen in a colony?
Form
Elevation
Margins
Size
Colour
38
Name a Beta haemolytic bacteria?
Group A streptococci
39
What type of haemolysis is partial, complete and no haemolysis.
Alpha - Partial
Beta - Complete
Gamma - None
40
How do serological tests help identify microorganisms?
Detect presence of specific IgM antibody to virus/microbe
41
What is 16sRNA
Ribosome that is different within bacteria compared with humans
Multiple types that can be carried by organisms
42
What can an immune under-reaction lead to?
Infection
Cancer
43
What can an immune over-reaction lead to?
Autoimmune problem
Allergic reaction
44
What are the constitutive barriers to infection?
Skin
Mucus
Commensal bacteria
45
What can be found in mucus to support its function?
Secretory IgA
Lysozyme
Defensins
Antimicrobial peptides
Lactoferrin - Starves of Fe
46
What is the difference between innate and adaptive immunity?
Innate immunity is continuously present from birth, the same generic response occurs to many microbial species.
Adaptive immunity is induced by the presence of foreign materials and generates a unique response to each individual pathogen.
47
What is the time period for innate and acquired immunity?
Innate - 0-96 hours
Adaptive - >96 hours
48
What are the immune cells of natural immunity?
Macrophages
Mast cells
NK cells
Neutrophils
49
What are mast cells?
Large tissue-resident cells
Granular
Pro inflammatory
Parasitic killing mechanisms
50
What are macrophages?
Large phagocytic cells
Important source of cytokines
Also promote tissue repair and limit acute inflammatory responses
51
What are natural killer cells?
Large granular cells
Detect and kill tumour cells and virally-infected cells
52
What are PAMPs?
Pathogen Associated Molecular Patterns
Signature molecules not found on human cells
53
What are PRRs?
Pattern Recognition Receptors
Receptors for PAMPs found on the cell surface and in the cytosol to detect pathogens
54
Describe phagocytosis stages.
PRRs are expressed on macrophages and neutrophils.
Binding to PAMPs signals phagocytic cup formation.
The cup extends around the target and forms a phagosome.
The phagosome fuses with lysosomes forming a phagolysosome to kill the pathogen.
Debris are released into extracellular fluid.
Pathogen derived peptides are expressed on cell surface receptors.
Pro-inflammatory mediators are released.
55
What is opsonisation?
The coating of pathogens by soluble factors to enhance phagocytosis
56
Give some examples of opsonins.
C3b
CRP
IgG/IgM
57
What are the 3 ways neutrophils can kill?
Phagocytosis
Degranulation
NETs
58
What are the 2 ways neutrophils can carry out phagocytosis?
Phagolysosomal killing
ROS-dependent killing
59
Describe degranulation.
Release of antibacterial proteins from neutrophil granules directly in the extracellular milieu
60
Describe neutrophil killing by NETs.
Neutrophil suicide to immobilise pathogens to prevent spreading and facilitate subsequent phagocytosis.
61
What are NETs composed of?
Genomic DNA
Histones
Granular proteins
Enzymes
62
What is released by virally infected cells?
Cytokines called interferons. Interferon alpha and beta signal neighbouring cells.
63
What do NK cells respond to?
MHC class 1 molecules
64
What happens when NK cells are activated?
They release perforin proteins that insert into the membrane of a target cell; forming a pore causing osmotic lysis of the target cell.
65
What is the role of CRP
Prime certain bacteria for destruction by the complement system and phagocytes. Functions as an opsonin.
66
What is the first acute phase protein of the complement system?
C3
67
What are the 3 pathways by which C3 can be cleaved?
Classical pathway
Mannose-binding lectin pathway
Alternative pathway
68
What is C3 cleaved into to become active?
C3a and C3b
69
What type of cells express mannose?
Certain bacterial species
70
What enzyme converts C3?
C3 convertase.
71
What does active C3b do?
Associates with other complement system proteins producing a C5 convertase cleaving C5
72
What do C3a and C5a do?
Anaphylatoxins - Promote vascular changes, acute inflammation and leukocyte recruitment
73
What protein in linked to MAC in the complement cascade?
C5b
74
How does C3b cause further cleavage?
Activates the alternative pathway through amplification loop
75
What are the 2 major categories of T cells?
CD4+
CD8+
76
What structures induce an adaptive immune response?
Antigens
77
What is an antibody?
Any substance that is produced in response to an antigen
78
What is a BCR?
B cell receptor, an antibody
79
What are the four polypeptide chains on an antibody?
2 x light chain
2 x heavy chain
80
What kind of antigens can be recognised by T cells?
Peptide antigens
81
What is a TCR composed of?
T cell antigen receptor
Alpha chain and beta chain held together by peptide bonds
82
What presents peptide antigens to TCRs?
MHC molecules
83
What are the main differences between class 1 and 2 MHCs?
Class one are expressed on all nucleated cells, class two only on professional antigen presenting cells (dendritic, macrophages and B cells)
Class one present to CD8+ and class two present to CD4+
84
Where do lymphocytes develop?
Initially bone marrow
T cells mature in the thymus
B cells mature in bone marrow
85
Where do T cells and B cells segregate to in secondary lymphoid tissues?
T cell and B cell zones
86
What do stromal cells do in secondary lymphoid tissues?
Found in B cell zone and catch and hold antigens to allow B cell activation
87
What cell displays peptides for T cells?
Dendritic
88
When activated what do B cells do?
Clonally proliferate
Differentiate into effector cells: Plasma and memory B cells
89
What do plasma cells do?
Produce and secrete soluble, antigen specific antibodies
90
What do memory B cells do?
Long lived cells that circulate the body
91
What is needed to activate a B cell?
Antigen binding and co-stimulation
92
What are the first antibodies to be secreted by short-lived plasma cells?
IgM
93
What antibody is low affinity but quickly made?
IgM
94
What can be the second signal for a B cell with a protein antigen?
T helper cells
95
How to B cells present MHC-II molecules?
The protein antigen bound to the BCR is internalised by the B cell and degraded, deriving peptides that are presented on the B cell surface in an MHC-II complex
96
Describe the germinal centre reaction?
Effector Tfh cells migrate into B cell zone and are re-stimulated by B cells in an antigen-specific manner. They then stimulate the B cell to clonally proliferate and differentiate into long-lived plasma cells that secrete high affinity antibodies.
97
What forms can IgM be found in?
Membrane-bound monomeric form
Secreted pentameric form
98
What is agglutination?
Action of an antibody when it cross-links multiple antigens producing clumps of antigen
99
What immunoglobulin classes mediate agglutination?
IgM and IgG
100
What is the most abundant antibody in normal human serum?
IgG
101
What are the functions of IgG?
Agglutination
Complement system activation
Foetal immune protection
Neutralisation
Opsonisation
NK cell activation
102
What is the function of IgD?
Membrane-bound monomeric form serves as B cell antigen receptor and mediates B cell activation
103
What is the function of IgA?
Monomeric form in serum functions in neutralisation
In secretory fluids dimeric form acts in neonatal defence and neutralisation
104
What type of antibody can trigger allergic responses?
IgE
105
Where are immature dendritic cells found?
Normal non-inflamed tissues
106
What can an activated CD4+ T cell differentiate into?
Th1 cells
Th2 cells
Tfh cells
Th17 cells
Regulatory T cells
107
What is Interleukin 2 (IL-2)?
T cell growth factor released by activated CD4+ T cells
108
What do Th0 cells do?
Induce autocrin/paracrine mediated proliferation of activated CD4+ and activated CD8+ T cells
109
What do effector Th1 cells do?
Enter sites of infection/inflammation and are re-activated by infected macrophages. They then secrete pro-inflammatory cytokines to enhance macrophage activating by stimulating production of reactive oxygen species.
110
When does ROS production supported by Th1 T cells help macrophages?
In killing pathogens that can evade normal phagolysosomal mechanisms
111
What do effector Tfh cells do?
In the B cell zone are re-stimulated by B cells (antigen-specific). When re-activated stimulate B cells to clonally proliferate and differentiate.
This is done by increasing cell surface co-stimulatory molecules and secreting cytokines to further activate the B cell.
112
What are the cells CD8+ T cells differentiate into known as?
Cytotoxic T lymphocytes (CTLs)
113
How do CTLs kill infected host cells?
Secretion of cytotoxic granules
Expression of Fas ligand
114
What cells contribute to immunological memory?
Memory CD4+ T cells
Memory CD8+ T cells
Memory B cells
Long-lived plasma cells
115
What is virulence?
The capacity of a microbe to cause damage to the host
116
Name some common protozoan diseases.
Malaria
Toxoplasma
Cryptosporidiosis
117
Name common Gram +ve bacteria.
Streptococcus spp.
Staphylococcus spp.
Enterococcus spp.
Clostridium
118
Name common gram -ve bacteria
Neisseria spp
Escherichia spp
Shigella spp
119
Name some gram -ve cocci and the diseases they cause.
Neisseria meningitidis - Commonest cause of bacterial meningitis
Neisseria gonorrhoeae - Causes gonorrhoea
120
What gram -ve bacteria are associated with the GI tract?
Commensal - Most E.Coli, enterobacter spp, klebsiella spp.
Pathogens - Salmonella spp, shigella spp, verotoxin producing E. coli
121
What are coliforms?
A species of gram -ve bacilli that look like E.coli on Gram film and when cultured on blood agar.
122
When can coliforms become problematic?
When they get into a normally sterile site, e.g. UTI
123
What is the first line treatment for infections caused by coliforms?
Gentamicin
124
What is sepsis?
A host response to severe infection mediated by LPS/endotoxin via host immune system
125
What occurs in sepsis?
Small blood vessels become "leaky" and lose fluid into tissues.
Lower blood volume increases HR to maintain oxygenation.
Poor perfusion means blood supply to non essential organs shut down to maintain supply to the brain.
The blood clotting system is activated causing clotting in tiny blood vessels, this uses up all clotting factors increasing haemorrhage risk.
126
What diseases are associated with streptococci A?
Streptococcal sore throat (Scarlet fever)
Invasive diseases e.g. necrotising fasciitis
Puerperal sepsis - Infection of pregnant and post natal women
127
What is streptococcus pneumoniae?
Gram +ve
Alpha haemolytic
Cocci
Commonest cause of pneumonia
128
What is the most important group of non-haemolytic cocci?
Enterococci
129
What is VRE?
Vancomycin resistant enterococci
130
Are staphylococci gram +ve or -ve?
Gram +ve
131
Name 3 types of staphylococci.
S.Aureus
S.Epidermidis
S.Saprophiticus
132
What kind of bacteria is MRSA?
S. aureus
133
What bacteria is the most common cause of skin, soft tissue and wound infections?
S.Aureus
134
Are clostridioides gram +ve or -ve?
Gram +ve
135
What is a viral particle composed of?
Nucleic acid genome
Protein capsid
Sometimes a lipid envelope
136
What are the phases of the viral growth cycle?
Attachment
Entry
Uncoating
Synthesis of Viral Components
Assembly and Release
137
How do enveloped viruses acquire their envelopes?
Budding
138
How do viruses damage the host?
Viral factors - Cell lysis, cell-cell fusion, inhibition of host transcription, alteration of host cell cycle
Host factors - Apoptosis, lysis of infected cells by immune cells, inflammation
139
How are viral infections diagnosed?
PCR
Antigen testing
Antibody testing
140
What can anti-viral drugs target?
Viral nucleic acid polymerases
Viral enzymes involved in nucleic acid replication or protein synthesis
Uncoating
Attachment/entry
Release
141
