Exam 3-Ch 20-25,27,32-36 Flashcards
1
Q
Virus
A
Genetic element that CANNOT replicate independently of a living/host cell
2
Q
DEFINITION OF: Virion/Virus Particle
A
Extracellular form of a virus that exists outside the host and facilitates transmission from 1 host cell to another
3
Q
STRUCTURE of Virion/Virus Particle
A
Nucleic acid genome surrounded by a protein coat and sometimes, other layers of material
-also contains enzymes necessary for infection
4
Q
Enzymes Found In Virion
A
- Lysozyme
- Polymerases
- Neuraminidases
5
Q
Function of Lysozyme
A
- Makes hole in cell wall
2. Lyses bacterial cell
6
Q
Function of nucleic acid Polymerases
A
- Replication fo viral genome
2. Transcription of virus-specific RNA
7
Q
Function of Neuraminidases
A
- Aids in release from the host
- Cleaves glycosidic bonds
- Allows liberation of viruses from cell
8
Q
What must all viral genomes make in order to be translated?
A
mRNA
9
Q
How are viruses classified?
A
Based on the hosts they infect
10
Q
What are the classes of viruses?
A
- Bacterial viruses (bacteriophages)
- Archael Viruses
- Animal Viruses
- Plant Viruses
- Other Viruses
11
Q
Nucleocapsid
A
Complete complex of nucleic acid and protein packaged in the virion
12
Q
What are the 2 kinds of symmetry a nucleocapsid can have?
A
- Helical/Rod-shaped
2. Icosahedral/Spherical
13
Q
Describe the helical structure of a nucleocapsid.
A
- Units of hollow tubes w/ protein walls assemble to form a cylindrical tube
- Within capsid, RNA genome is wound up and lies in a groove formed by the protein subunits
14
Q
Describe the icosahedral structure of a nucleocapsid.
A
- 20 equilateral triangular faces + 12 vertices
2. most efficient arrangement of subunits in a closed shell
15
Q
Naked Nucleocapsid
A
Consists of nucleic acid, capsid, and some enzymes needed for replication & infection
16
Q
Enveloped Virus
A
Virus that contains additional layers around the nucleocapsid
17
Q
What type of cells do enveloped viruses infect and why?
A
Eukaryotic cells
Why: virus envelope contains phospholipids which aren’t normally found in bacterial or prokaryotic cells
18
Q
What happens when the enveloped virus exits the host cell?
A
It takes a bit of the host cell membrane (in the form of an envelope)
-in envelope, some/all reg cell membrane proteins are replaced w/viral proteins & some proteins form a binding layer b/w the envelope & capsid
19
Q
Spikes/Peplomers
A
Glycoproteins found on the outside of the envelope
- essential for attachment
- can be used to identify virus b/c shape is cell specific
20
Q
Complex Viruses
A
Virions composed of several parts, each w/ separate shapes and symmetries
21
Q
Bacteriophage
A
Viruses that infect bacteria
-Structure=icosahedral heads + helical tails
22
Q
Name 2 characteristics that differentiates the Mimivirus from small obligate intracellular bacteria.
A
- Mimivirus particles don’t undergo division but are formed by assembling preformed components
- Mimivirus has no protein translation apparatus (ribosomes) and no systems to produce biological energy (ATP)
23
Q
Capsid
A
protein shell that surrounds the genome of a virus particle
-made of a # of protein molecules arranged in a precise & highly repetitive pattern around the nucleic acid
24
Q
Capsomere
A
subunit of the capsid
25
Self-Assembly
Capsomeres generally self-assemble themselves around the nucleic acid
26
Protomers
Protein subunits that make up capsomers
27
Why is a host so important to a virus?
In order for the virus to replicate, it must use the host cell's machinery to make more virions
28
What are the 5 phases of Viral replication?
1. Attachment/Adsorption
2. Pentration/Entry
3. Synthesis
4. Assembly
5. Release
29
Attachment/Adsorption
Virus attaches to a susceptible host cell
30
Penetration/Entry
Virion or its nucleic acid enters the cell
31
Synthesis
Virus redirects host cell machinery to synthesize virus's nucleic acid and protein by cell metabolism
32
Assembly
self assembly apsids and viral genomes are packaged into new virions (maturation)
33
Release
Mature virions are released from the host cell
34
What are the 2 ways virions can be released from the host cell?
1. Budding (if enveloped virion)
| 2. Lysing (if naked virion)
35
What are the 2 phases of the latent period (virus replication)?
1. Eclipse
| 2. Maturation
36
Eclipse Period
Early enzymes and nucleic acids are made
| -no infectious particles present
37
Maturation Period
Protein coats for virions are made
38
Burst Size
Characteristic number of virions released after each replication cycle (specific to each virus)
-can range from a few to thousands
39
Length of replication cycle in bacteria viruses vs animal viruses?
Bacteria=20-60 mins
| Animal=8-40 hrs
40
Burst TIme
Time from phage (virus) adsorption to release
41
What does a virion require in order to attach to a specific host cell?
Complementary Receptors
42
Complementary Receptors
- Found on the surface of susceptible host and its infecting virus
- Can be a protein, carbohydrate, glycoprotein, lipids, lipoproteins or complexes
- in host cells, they carry out normal cell functions (Ex. uptake of proteins)
43
What happens when a virus attaches to a host cell?
Surface of cell and virus changes to facilitate penetration
44
Permissive Cell
Host cell that allows the complete replication cycle of a virus to occur
45
3 ways virion/genetic matter goes into host cell
1. Fusion (mainly by enveloped virions)
=of viral envelope w/ host membrane->nucleocapsid enters
2. Endocytosis (by both naked & enveloped virions)
=in vesicle; endosome aids in viral uncoating
3. Injection (mainly by complex virions)
=of nucleic acid
46
Bacteriophage T4
Virus of E.coli
47
Steps of Bacteriophage T4 Penetration Mechanism
1. Attach to cells via tail fibers that interact w/ polysaccharides on E.coli cell envelope
2. Tail fibers retract & tail core makes contact w/ E.coli cell wall
3. Lysozyme-like enzyme forms small pore in peptidoglycan
4. Tail sheath contracts & viral DNA passes into cytoplasm
48
Eukaryotic Host Defense Mechanisms
1. Immune Defense Mechanism
| 2. RNA interference (RNAi)
49
RNA interference (RNAi)
Detects foreign RNA and cuts it up
50
Prokaryotic & Archaic Host Defense Mechanisms
1. CRISPR
| 2. Restriction Modification System
51
Restriction Modification System
DNA destruction system that only works against double stranded DNA viruses (i.e. ssDNA and ALL RNA viruses are unaffected)
-uses restriction enzymes/endonuceases to cleave DNA at specific sequences
52
Why does the restriction modification system not destroy DNA of host cell?
Modification of host's own DNA at restriction enzyme recognition sites prevents cleavage of own DNA
53
Viral/Bacteriophage Defense Mechanisms
1. Chemical modification of viral DNA
2. Production of proteins that inhibit host cell restriction system
3. Contain restriction systems to destroy host DNA
54
2 examples of Chemical modification of viral DNA
1. T-Even bacteriophages GLUCOSYLATE their DNA to prevent endonuclease attack
2. METHYLATE their DNA
55
When does chemical modification of viral DNA occur?
After genomic replication by modification proteins encoded by the virus
56
CRISPR Defense
Adaptive immune system that transforms elements of invading phages into RNA that matches the phage's nucleic acids
-This signals the bacteria to the presence of foreign genetic material, thus inducing the destruction of the phage
57
Bacteriophages Method To Evade CRISPR Defense
Developed its own CRISPR/Cas system that destroys the bacteria's version
58
Types of Viral Genomes
```
DNA: double & single stranded
Double stranded can be linear or circular
RNA: double & single stranded
3 types of single stranded RNA:
1. + 2. - 3. segmented
```
59
Positive Sense (+) RNA
Genomes that are ready for immediate translation into proteins
60
Negative Sense (-) RNA
Genomes have to be converted into the proper form to be made into proteins
61
Segmented RNA
Individual genes exist on sep pieces of RNA
62
Once a host has been infection, what must the virus do first?
Generate messenger RNA (mRNA)
63
RNA replicase
Specific RNA-dependent RNA polymerase needed by all RNA viruses to create DNA template needed to make RNA
64
What's the method?: dsRNA (+/-) virus-->mRNA(+)
Transcription of minus strand
65
What's the method?: ssRNA(+) virus-->mRNA(+)
Used directly as mRNA
66
What's the method?: ssRNA(-) virus-->mRNA(+)
Transcription of minus strand
67
What's the method?: ssRNA(+) retrovirus-->mRNA(+)
1. Reverse transcription
2. Forms dsDNA intermediate
3. Transcription of minus strand
68
What's the method?: dsDNA(+/-) virus-->mRNA(+)
Transcription of minus strand
69
What's the method?:ssDNA(+) virus--?mRNA(+)
1. Synthesis of other strand
2. dsDNA intermediate
3. Transcription of minus strand
70
Positive-strand RNA virus
Single-stranded RNA genome w/ same orientation as its mRNA
71
Negative-strand RNA virus
Single-stranded RNA genome with orientation complementary to its mRNA
72
Retrovirus
Animal virus responsible for causing certain types of cancers and AIDS (acquired immunodeficiency syndrome)
73
Where are DNA viruses replicated and assembled in a eukaryotic host cell?
Host cell's nucleus`
| =b/c it must be converted into a messenger RNA (which occurs in nucleus) to start protein synthesis
74
Where are RNA viruses replicated and assembled in a eukaryotic host cell?
Host cell's cytoplasm
| -doesn't need to go into nucleus b/c it's already in RNA form
75
Differences between early proteins and late proteins
Early: act catalytically, made in small amounts, made soon after infection
Late: structural components (ex. head & tail), made in large amounts, made later
76
Importance of Early Proteins
Necessary for replication of virus nucleic acid
77
Importance of Late Proteins
Components of virus coat
78
Generally, what sizes do viruses range between?
0.01-0.4 micrometers
79
How many steps are in the budding process, and what type of virus does this?
Steps: 4
Done By: Enveloped Viruses
80
1st Step of Budding
1. Viral envelope proteins are inserted into host cell's plasma membrane and line the cytoplasmic side of plasma membrane
81
2nd Step of Budding
2. Nucleocapsids are directed to plasma membrane by host cell's microtubules
82
3rd Step of Budding
3. Host cell's plasma membrane protrudes outward & nucleocapsids become surrounded by matrix-lined plasma membrane
83
4th Step of Budding
4. Neck of protruding membrane is pinched off and the mature virus is released
84
What are common characteristics of Bacteriophages/Bacterial Viruses?
1. Genome= dsDNA
2. Naked (although some have lipid envelopes)
3. Structurally complex (ie have heads, tails, etc)
85
What are the 2 types of viral life cycles?
1. Virulent Mode
| 2. Temperate Mode
86
Virulent Mode
Viruses lyse host cells after infection
| -generally an active virus and released via lytic mode
87
Temperate Mode
Viruses replicate their genomes IN TANDEM w/ host genome WITHOUT killing host
- virus can be lysogenic OR passive
- in animal viruses, this is a 'latent' infection
88
What type of genome did the first viruses have and who did they infect?
Genome: linear, dsDNA
Infected: Enteric Bacteria
89
What is significant of the DNA of T4 that makes it resistant to all known restriction enzymes?
- contains the modified base, 5-hydroxymethylcytosine
- modification is on cytosine where a H is replaced by CH2OH which is the site of glucosylation
- how? b/c T4 encodes its own nucleotide so it can modify cytosine rather than using host cell's cytosine
90
How long does it take the T4 bacteriophage to complete its life cycle (ie attachment->lysis)?
Less than 20 minutes
91
What type of bacteriophage is T4?
Virulent (i.e. release from host cell is via lysis)
92
What does the control of T4 mRNA synthesis in the host cell require?
Production of proteins that sequentially modify the specificity of the host RNA polymerase so that it recognizes phage T4 middle promoters and guides RNA polymerase to these sites
93
How do T4 early promoters make proteins?
1. Must be ready by HOST RNA polymerase
| 2. Requires HOST sigma factor
94
What happens after T4 early promoters make early proteins?
Phage makes phage-encoded anti-sigma factor which binds to host sigma factor and shuts it down
95
What is the function of phage-specific proteins (T4)?
Modify RNA polymerase
96
What does the transcription of T4 late promoters require?
New T4-encoded sigma factor.
97
How does T4 increase the efficiency of phage production?
Digests the host DNA
98
What is the function of T4 late genes?
Express enzymes that lyses the cell wall to release progeny phages
99
Which parts of host translation does the virus takeover?
1. mRNA availability to cytoplasmic ribosomes
2. cell signaling pathways that regulate translation factor abundance, localization & activity
3. ribosome recruitment
100
What are the factors that determine the strategy the virus uses to take control of host cell's translation process?
1. Virus life cycle
2. Type of host cell it infects
3. Method of host cell's translation control
101
What does it mean when we say the T4 DNA is TERMINALLY REDUNDANT?
Base sequence is repeated at both ends
102
What is the benefit of having terminally redundant ds DNA?
Allows for formation of concatamers
103
Concatamers
Long strands of DNA consisting of several units linked together
-allows for more accurate cleaving of genome for viral progeny packaging
104
How is bacteriophage dsDNA packaged into the viral head?
1. Terminase attaches to end of concatamer
2. Terminase docks DNA onto the procapsid portal of the viral feed
3. DNA gets injected into the head
4. Terminase cuts the DNA and ends packaging
5. A cap is used to block the procapsid portal and stabilize capsid
105
Terminase
Phage-encoded enzyme used in dsDNA packaging
106
Procapsid portal
Region on viral head where viral DNA is inserted
107
Temperate Phage
Special DNA phages that undergo adsorption & penetration but are NOT replicated or released immediately
108
Prophage Stage
Inactive stage where temperate phages insert their DNA into the host's chromosome
109
Lysogeny
Stage where the host chromosome carries the bacteriophage DNA
- temperate phage DNA gets copied along w/ host's so host cell's progeny will contain temperate phage DNA
- >can lead to lysogenic conversion
110
Lysogen
A bacterium containing a prophage
111
Lysogenic conversion
When a bacterium acquires a new trait from its temperate phage
112
Prophage
A phage that has inserted its DNA into the host's chromosome and enters an inactive stage
113
What type of phage is the lambda phage?
A temperate phage
| -i.e. it can either go into the lytic cycle or lysogenic cycle
114
In what ways can the temperate phage change the phenotype of its host?
1. Bacteria can become immune to superinfection
| 2. Phage may express pathogenic toxins or enzymes useful to bacteria
115
Name 2 advantages of lysogeny for viruses.
1. Phage remains viable and protected in genome but may not replicate
2. Multiplicity of infection ensures survival of host cell and therefore survival of virus
116
Induction
Synthesis of new phage particles (initiated by a change in cell conditions) to mediate release of phage particles via lysis
117
Characteristics of Lambda Phage
1. Linear, dsDNA genome
| 2. Has complementary single stranded cohesive end regions
118
Cohesive End Regions
Regions of DNA 12 nucleotides long found at the 5' terminus of each strand of dsDNA
119
What happens to the lambda phage's dsDNA upon penetration?
1. Cyclizes and forms a double stranded circle
| 2. cos site is formed via connection of cohesive ends
120
Where in E.coli's chromosome does the lambda DNA insert itself when the lambda phage is lysogenic?
At the lambda attachment site (attlambda)
121
What's needed in order for lambda DNA to attach to E.coli's chromsome at the attlambda?
Lambda integrase.
- cuts both E.coli chromosome and lambda cyclic DNA to make staggered ends
- DNA ligase used to seal the pieces together
*cos site is not where integrase cuts cyclic DNA
122
What controls whether the lytic cycle or lysogeny occurs?
Genetic Switch
123
How are linear concatemers of DNA synthesized by the lambda phage?
Via rolling circle replication
124
Describe the 2 stages of rolling circle replication.
1. One strand is nicked by endonuclease, a long ss concatamer is made from 5' end of the intact strand
2. 2nd strand is made using the ss concatemer as a template
125
Key Promotor Proteins In Genetic Switch
1. cl protein/lambda repressor
2. Cro repressor
- they lie on opposite sides of the operator region
- each controls direction of transcription which determines which cycle phage enters
126
cl protein/lambda repressor
Protein that causes repression of lambda lytic events by preventing all transcriptions except from PRM via repression of other lambda-encoded proteins
-commits lambda phage to LYSOGENY
127
Cro repressor
1. controls activation of lytic events by repressing PL and PRM which indirectly represses expression of the lambda cII and cIII proteins
- when made in large amounts, commits lambda phage to LYTIC CYCLE
2. increases transcription of itself (Cro)
3. increases transcription of Q
128
cII and cIII proteins.
Lamba proteins needed to induce synthesis of cI and to maintain lysogeny
129
what is the relationship and its importance between cII and cIII?
cIII protects cII against attacks from host cell's protease (FtsH-HflB)
importance: keeps cI stable
130
List the proteins key in maintaining that transcription of a temperate phage favors lysogeny?
1. Activated PL & PRM
2. N (anti-terminator)
3. Q (anti-terminator)
4. cII & cIII
131
Function of the anti-terminators N
Prevents the production of late proteins and lysis
132
What 2 things are accomplished with high levels of cII to promote lysogeny?
1. ↑ in int(integrase) gene transcription which catalyzes integration of lambda into host genome
2. ↑ transcription of cl gene (ie lambda repressor) by binding to PRM promoter which activates transcription of cI
133
Function of Q
Activates genes needed for the lytic cycle
134
In order for lysis to occur, what must the prophage do?
Site Specific Recombination
135
Site Specific Recombination
1. 2 ends of phage genome exchange their phosphodiester backbone linkages in order to separate from the host molecule
2. phage DNA circularizes and initiates a lytic cycle
*when exiting, can pick up some of host cell's genes
136
Factors That Can Cause Exit From Lysogeny
1. Random
2. Triggered by environmental stress (ex. uv light)
3. Events that threaten host survival
137
What type of genome do most archaeal viruses have?
dsDNA
| -can be linear or circular
138
What defines a new archaeal virus family?
Unusual morphologies
139
What is significant of the archael virus, Sulfolobus turreted icosahedral virus (STIV), method of release from the host cell?
Rather than lysing or budding, it starts structural formation on the external cell surface of host-->creates these pyramid-like surfaces, builds until it releases (so kind of like slow budding)
140
What are the 4 possible consequences of viral infections in animal cells?
1. Persistent Infections
2. Latent Infections
3. Transformation
4. Cell Fusion
141
Persistent Infections
Virions are released from host cell w/out resulting in cell lysis
-infected, intact cell remains alive and continues to produce and release virus
142
Latent Infection
Delay between infection by the virus and lytic events
143
Transformation
Conversion of normal cell into tumor cell
144
Cell Fusion
2 or more cells become 1 cell with many nuclei
145
What type of genome does the poliovirus have?
Positive-Strand RNA
146
What happens first to the poliovirus genome when it enters a eukaryotic cell?
Its ENTIRE genome gets translated DIRECTLY and produces a polyprotein that undergoes self-cleavage to make 20 smaller proteins needed for nucleic acid replication and virus assembly
147
Polyprotein
Single long, giant protein
148
Does the polyprotein of the poliovirus contain replicase?
Yes
149
Herd Immunity
State where a large enough fraction of the population is immune to a disease that it decreases the risk of someone getting the disease to ~0%
150
How many cases of mumps have been confirmed in an outbreak at Ohio State University?
37
151
Describe the structure and type of genome the Mumps Virus (MuV) has.
Genome: single stranded neg-sense RNA
Structure:
- spherical
- enveloped
- F glycoprotein spikes
152
What species does the MuV infect?
Only humans
153
Describe the structure and type of genome of the Coronavirus (CoV)
Genome: positive strand RNA virus
Structure:
- club-shaped glycoprotein spikes on surface
- produces monocistronic mRNA
154
Monocistronic mRNA
mRNA that only codes for 1 specific protein
155
What do coronaviruses cause?
Respiratory infections such as SARS
156
Where does replication and assembly of the coronavirus occur within the cell?
Replication=In cytoplasm
Assembly=In golgi
157
How is the mRNA of the coronavirus transcribed?
1. translation of (+) strand mRNA to make complementary (-) mRNA
2. (-) mRNA strand is transcribed by RNA replicase to make both monocistronic mRNAs and copies of (+) mRNA
158
In humans, where is the major site of coronavirus replication?
Epithelial cells of the respiratory tract
159
What is MERS (middle east respiratory syndrome)
Type of coronavirus that can be spread person to person, also leads to respiratory infections
-originated from an individual's exposure to bats or camels
160
How are negative-strand RNA viruses able to be translated in the host cell?
Virus brings its own enzyme to use for transcription.
161
Describe the genome and type of virion the influenza virus is.
Genome: negative strand RNA
-segmented genome
Virion: enveloped polymorphic virus
162
What are the 2 types of surface proteins found on the influenza virus that interact with the host cell surface.
1. Hemagglutinin
| 2. Neuraminidase
163
Function of Hemagglutinin
Causes clumping of red blood cells
164
Function of Neuraminidase
Breaks down sialic acid component (found on surface of epithelial cell) of host cytoplasmic membrane
-aids in attachment
165
What are the differences between the 3 subtypes (A,B,C) of the influenza virus?
A: can cause flu-like symptoms and those within this type are named according to types of H and N spikes displayed on their surface. infects a wide variety of mammals and main cause of human epidemics & pandemics
B: cause flu-like symptoms but not as severe as A and not subdivided
C:also infects mammals but rarely cause disease. genetically and morphologically dif from A and B
166
Describe the adsorption of the influenza virus into the host cell.
1. HA spikes bind to mucoproteins containing terminal N-acetyl neuramini acid (NANA=sialic acid) groups
2. virus is engulfed into endocytotic vesicles and then into endosomes via endocytosis
167
What happens after the influenza virus is adsorbed into host cell?
1. Ribonuclear proteins are translocated to the nucleus
| 2. Genome segments are transcribed by 3 polymerase polypeptides associated w/ each genome segment
168
Antigenic Drift
Structure of neuraminidase and hemagglutinin proteins (on influenza proteins) are subtly altered
-leads to minor changes & epidemics; occurs every 2-3 yrs
169
Antigenic Shift
Portions of the RNA genome from 2 genetically distinct strains of virus infecting the same cell are reassorted-->generates virions that express a unique set of surface proteins
-leads to major changes & pandemics; occurs every 10 yrs
170
What is the cause behind the species barrier for the influenza virus?
Type of species a specific type of influenza virus is able to infect is determined by dif forms of sialic acid present on the virus glycoproteins (in particular, on the haemagglutinin protein)
171
What type of genome does the phiX174 bacteriophage have?
Circular (+) single-stranded DNA contained within an icosahedral virion
172
What do phiX174 virus particles use to bind to target cells?
Lippolysaccharides (LPS)
173
What happens to the phiX174 DNA once its been injected by the capsid proteins into the host cell's cytoplasm.
1. ssDNA gets coated with host SSBs and is immediately rendered super coiled
2. Host polymerase converts the supercoiled (+) ssDNA into replicative form DNA I (RFI)
174
Replicative Form DNA/ ds RFI DNA
Made via replication of supercoiled SSDNA by host polymerase
| -Used to produce more phiX174 (+) ssDNA forms which in turn will generate more RF forms
175
Describe the state of the early viral genes within 20-30 mins of infection by phiX174.
Early viral genes are transcribed by host RNA polymerase and produce viral replication proteins
-Within this time frame, they will produce a sufficient amount of viral A protein
176
Viral A Protein
- Cleaves RFI DNA (+) strand at origin of replication
- Initiates replication by covalently attaching itself to the DNA
- RFII molecule is generated
- Cleaves and ligates new strand after 1 new progeny strand has been created (ie 1 revolution)
177
How does (+) strand replication of phiX174 occur?
via rolling circle replication
178
Where does procapsid assembly and maturation for phiX174 occur within the host cell?
Cytoplasm
179
Are the late viral genes of phiX174 transcribed by the host's or the virus's RNA polymerase?
Host's
180
Function Viral Protein C
Binds to replication complex and induces packaging of newly synthesized (+) DNA into procapsids
181
How are progeny phiX174 phages released from the host cell?
1. Viral lysozymes attack the host cell's peptidoglycan walls
2. Lysis occurs
182
Describe the genome and structure of T7.
Genome: linear dsDNA
-genome always enters host cell in SAME orientation
Structure: icosahedral head and very short tail
183
Why must the T7 genome always enter the host cell in the same orientation?
B/c the order of genes on the T7 chromosome influences regulation of virus replication
184
What does the T7 bacteriophage infect?
E.coli
185
Describe T7 DNA replication.
- Uses T7 DNA polymerase
- Involves terminal repeats and formation of concatamers
- Characteristic bubble & Y forms
186
What are concatamers made from in T7 DNA replication?
Unreplicated portions are paired via T7 phage polymerase and then ligased
187
Where can pathogens come from?
Animate: humans, animals
Inanimate: water, soil, food
188
What do we call an infection when it's passed from animal to human?
Zoonoses
189
What do we call the natural environmental location in which a pathogen normally resides?
Reservoir
190
What do we call a situation in which a microorganism is established and growing in a host, whether or not the host is harmed.
Infection
191
Define: immunity
the active ability to resist disease
192
What is the difference between infection and disease.
Disease is the pathologic state that results when the infection damages/disrupts tissues and organs
193
Define: Disease
Damage/injury to the host that impairs host function
194
Name 2 things a pathogen must overcome in order to infect the host.
1. Overcome surface barriers in order to reach underlying tissue
2. Overcome resistance by host
195
Name 2 kinds of resistance the host cell puts up against a pathogen.
1. Nonspecific resistance (innate)
| 2. Specific immune response (adaptive)
196
What is the function of the immune system?
To recognize foreign substances/microbes and act to neutralize/destroy them
197
Ability of host to resist a particular disease/infection
Immunity
198
Describe the nonspecific immune response
- acts as the 1st line of defense
- offers resistance against ANY microbe/foreign material
- lacks immunological memory
199
Describe the specific immune response
- offers resistance against a SPECIFIC foreign agent
| - has immunological memory which increases effectiveness on repeated exposure to agent
200
What does a pathogen need in order to survive?
1. A host (i.e. suitable environment)
2. A source of nutrients
3. Protection from harmful elements
201
What tool does the pathogen have to help protect it from harmful elements?
Virulence factors
202
What are the 6 general steps of pathogen infection?
1. Exposure to pathogens
2. Adherence to skin/mucosa
3. Invasion through epithelium
4. Colonization & growth (production of virulence factors)
5. Toxicity-can be local or systemic
6. Invasiveness: further growth at original & distant sites
- all lead to tissue damage/disease
203
Where does the pathogen enter the host?
Portals of entry
| ex. skin, gastrointestinal, respiratory, blood transfusion, etc
204
What are the structures a pathogen uses to adhere to the host cell?
Pili/fimbriae and adhesins that bind to complementary receptor sites on host cell
205
What is Virulence?
The degree/intensity of pathogenicity.
206
What determines the degree to which the pathogen causes damage, invasion, and infectivity?
- Virulence factors
| - pathogen's ability to survive outside the host
207
Define: Toxigenicity
Ability to produce toxins
208
Define: Toxin
Specific substance that damages host
209
Define: Intoxications
Diseases that result from entry of a specific preformed toxin into host
210
Define: Toxemia
Condition caused by toxins in the blood of the host
