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Microbiology 210 > Lecture Exam 3 > Flashcards

Lecture Exam 3 Flashcards

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1
Q

What are the general characteristics of viruses?(5)

A
  • Obligate intracellular parasites
  • Not cellular
  • Structure: capsid surrounds nucleic acid core
  • Nucleic acid either DNA or RNA
  • N.A. either single stranded or double stranded
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2
Q

What is the term for the fully formed virus that is able to establish an infection?

A

Virion (viral particle)

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3
Q

What are viruses classified by?

A

Structure, genetic material, replication strategy
Classification by covering:
- Capsid - protein shell
- Envelope - most human viruses
Classification by central core:
- Nucleic acid molecules - DNA/RNA
- Marix proteins enzymes

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4
Q

Are antimicrobial drugs and chemicals (antiseptics and disinfectant) more likely to be effective towards naked or enveloped viruses? Why?

A
  • Antimicrobials are more effective against enveloped viruses
  • Lipid envelope can be easily disrupted as opposed to protein capsid that non-enveloped viruses have
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5
Q

What are the two parts of the nucleocapsid?

A

Capsid - Protein coat that encloses and protects nucleic acid
Nucleic acid - Single/double stranded DNA/RNA

Both together form the nucleocapsid

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6
Q

What nucleic acid(s) are found in viruses? What are some of the possible structures of viral DNA (e.g single stranded, circular, etc.)? What types of genes are typically in a viral genome?

A
  • Viruses can have either DNA or RNA
  • Viral nucleic acids can be either single stranded or double stranded
  • Carries genes necessary to invade host cell and redirect cell activity to viral formation
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7
Q

What is a capsid and what is it made of?

A
  • A protein coat that encloses and protects nucleic acid
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8
Q

What are the identical protein subunits called that make up a capsid called?

A

Capsomers

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9
Q

What is the viral envelope and what is it composed of? Where is the viral envelope, relative to the capsid (inside or outside?)? Are enveloped viruses monomorphic or pleomorphic? What advantage does the viral envelope give a virus?

A
  • Outer lipid membrane
  • Outside of capsid
  • Pleomorphic
  • Exposed proteins (spikes) are essential for attaching to host cells in addition to lipid membrane making invading host easier through membrane fusion
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10
Q

What are the spikes used for on a viral envelope?

A
  • Found in both enveloped and naked viruses
  • Essential for binding to host cells
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11
Q

What are the 4 enzymes that viruses can produce? Which enzyme do retroviruses use to direct the formation of DNA from RNA?

A

DNA Polymerase:
- Replicates and transcribes viral DNA
RNA Polymerase:
- Replicates and transcribes viral RNA
Replicase:
- Creates RNA copy
Reverse transcriptase: (only retroviruses)
- Synthesize DNA from RNA
Lysozyme:
- Degrades cell wall (phage)

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12
Q

What do we call the virus capsid shape that is a hollow cylinder with nucleic acid inside? What do we call the virus capsid shape that is many sided? What are the other two capsid shapes and what do they look like?

A
  • Helical capsid
  • Polyhedral
  • Complex - Unusual shape
  • Enveloped - Polymorphic
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13
Q

Describe the 6 steps in animal virus replication.

A
  1. Adsorption - binding of virus to specific molecule on host cell
  2. Penetration - genome enters host cell
  3. Uncoating – the viral nucleic acid is released from the capsid
  4. Synthesis – viral components are produced
  5. Assembly – new viral particles are constructed
  6. Release – assembled viruses are released by budding (exocytosis) or cell lysis
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14
Q

True or False. A specific animal virus has the ability to attach to and enter almost any animal host cell. Explain you answer.

A

False - Most viruses are specific to their host species and rarely jump from one species to another

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15
Q

What is host range? What does host range depend on?

A
  • Host range refers to the ability for a virus to infect
  • Host range can be narrow (only for a specific type of cell) or be broad (can infect a wide range of cells)
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16
Q

Does hepatitis B have a narrow or a broad host range? What type of cells can the hepatitis B virus infect? What about rabies?

A
  • Hepatitis has a narrow host range as it can only infect human liver cells
  • Rabies can infect various animal cells and has a broad host range
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17
Q

How does virus adsorption occur for animal viruses? How is this different between enveloped and non-enveloped viruses?

A
  • Always occurs via receptors
  • Enveloped viruses have membranes that fuse to host cells
  • Non-enveloped viruses are engulfed then broken down inside the cell
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18
Q

What are the two ways through which animal viruses penetrate the host cell?

A

Endocytosis: Virus is engulfed then when vesicle breaks down nucleic acids are released
Fusion: Virus outer membrane merges with host membrane and nucleic acids are released

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19
Q

Which term refers to the gradual release of viruses by an infected cell that is not immediately lysed? What term refers to when nonenveloped and complex viruses are released when the host cell dies and ruptures?

A

Budding: Nucleocapsid binds to membrane and sheds virus gradually

Lysis: Nonenveloped and complex viruses released when cell dies and ruptures

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20
Q

What are 3 ways that animal viruses are grown in the lab?

A
  • Living animals
  • Embryonate eggs
  • Cell cultures
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21
Q

What are cytopathic effects and what are some examples of cytopathic effects? (7)

A

Virus induced damage to cells
1. Change size and shape
2. Cytoplasmic inclusion bodies
3. Nuclear inclusion bodies
4. Cells fuse forming multinucleated cells
5. Cell lysis
6. Alter DNA
7. Transform cells to cancerous cells

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22
Q

How are viruses identified? What is the MOST common way that viruses are identified?

A

1) Cytoplasmic effects
2) Serological test: ex. western - most common
3) Nucleic acids: ex. PCR amplification and detection of viral DNA

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23
Q

What are the 3 main categories for how antiviral drugs work (you do not need to know the examples given)?

A

Viral DNA Poly inhibitor:
- Prevents DNA formation
Reverse transcriptase inhibitor:
- Prevents reverse transcription (RNA->DNA)
Viral RNA Poly inhibitor:
- Prevents the replication of viral RNA

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24
Q

What are interferons used for?

A

To prevent the spread of viruses to new cells. Inhibit viral replication and cancer cells

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25
What is required for a virus to multiply in a host cell? (2)
- Must invade host cell - Must control metabolic activity
26
Describe the difference between acute, latent, and persistent viral infections. What is an example of each?
Acute: - Rapid effect that is short lived as host immune system suppresses - Flu Latent: - Infection remains asymptomatic for long periods but reactivates periodically - Cold sores Persistent: - Cell harbors virus and is not immediately lysed - HPV can lead to cancer
27
What do we call mammalian viruses capable of initiating tumors?
Oncoviruses - Papillomavirus - Epstein-Barr
28
What do we call viruses that infect bacteria?
Bacteriophage - Release of nucleic acids only occurs via lysis
29
What step happens in animal virus multiplication, but doesn’t happen in bacteriophage multiplication?
- Uncoating is when only nucleic acids are released when inside a cell - Virus only relased via lysis in bacteria
30
How are bacteriophage grown in the laboratory?
Grown in bacteria by infecting cells and isolating resulting in plaques
31
What is a plaque and what does each plaque correspond to?
Plaques are areas where a bacteria was lysed by viral infections
32
What are the 5 stages in the lytic cycle of bacteriophage multiplication? Describe each step.
1) Attachment: phage attaches by tail fibers to host cell 2) Penetration: phage lysozyme open cell wall; tail sheath contacts to force tail core and DNA into cell 3) Biosynthesis: production of phage DNA and RNA inside the bacteria 4) Maturation: assembly of phage particles into varions (complete infectious virus) 5) Release: phage lysozyme breaks cells wall and new formed viruses are released
33
Which structure on bacteriophage allow them to attach to host cell receptors?
Tail fibers
34
What enzyme do phage produce that allow them to break down bacterial cell walls so that they may inject their DNA into a host cell?
Produce lysozyme to degrade bacterial cell wall and inject DNA
35
How are phage released from bacterial cells?
Once the virus has multiplied it will fill a bacteria and lyse releasing the viruses to infect other host cells
36
What is the lysogenic cycle in bacteriophage? What happens during the lysogenic cycle?
Lysogenic phage cause a silent infection in bacteria - Bacteria may undergo lysogenic conversion and gain genes to produce deadly toxins - Can cause increased virulence due to phages
37
What are prions, satellite viruses, and viriods?
Prions: - Misfolded proteins containing no nucleic acid - Causes transmissible encephalitis (ex. Mad cow) - Extremely resistant to sterilization Satalite viruses: - Viruses dependent on other viruses for replication - Only replicate in cells infected with adenovirus - Delta agent (naked RNA from Hep B) Viriods: - Short pieces of RNA - No protein coat - Only in plants
38
Define adaptive and innate immunity.
Innate immunity: - Non-specific - 2 lines Adaptive immunity: -Specific -3rd line with two branches
39
What are the two main categories of the 1st line of defense?
Barriers to entry: - Skin, mucous membranes, sweat/sebaceous glands, cilia, excretion, flora, and reflexes (blinking/sneezing) Chemicals: - Lysozymes (tears/saliva), pH, sebum, meibomian glands
40
What are examples of physical barriers in the 1st line of defense and describe how each one works as a barrier? (7)
Skin - Physical barrier Mucous membrane - Makes cells hard to reach Sweat/sebaceous glands - Salt/pH decrease Cilia - Transport foreign substances out of the body Excretion Flora - Creates environment where pathogens must compete Reflexes - Blinking, coughing, diarrhea
41
What are the chemical factors used in the 1st line of defense and how does each one work?
Lysozymes - Destroy bacterial cell walls pH - Creates hostile environment for microbes Sebum - Lowers pH and creates protective lipid layer Meibomian glands - Flush eyes (crying)
42
Describe the role of normal microbiota in innate immunity
Compete with pathogens via microbial antagonism (production of antimicrobial substances)
43
What are the four categories that are involved in the 2nd line of defense?
Cellular - Phagocytes and Natural Killer Cells Inflamatory response - Response to tissue damage Metabolic response - Fever and iron removal Chemicals - Interferons and complement
44
Which types of white blood cells function as phagocytes and what is each cell type used for?
Neutrophils - 1st responders, most phagocytic Eosinophils - Fights worms, allergic response, and phagocytosis Monocytes - Become fixed and wandering macrophages
45
Which white blood cell is considered the first responder in innate immunity?
Neutrophil
46
Which leukocyte can be activated to develop into macrophages?
Monocytes
47
What are natural killer cells, how do they kill foreign invaders, and what types of pathogens are they used against?
- Kill Protozoans, fungi, Virally-infected host cells, Cancer cells - Lymphocytes - Chemically kill
48
What line of defense is the inflammatory response? What is it in response to and what are the symptoms of it?
- Second line of defense - Response to tissue damage causing Redness, heat, pain, and swelling - Vasodilation and permiability, phagocytic migration, repair
49
What are the steps of the inflammatory response?
1. Vasodilation and increased permeability - Blood vessels increase in diameter and defensive materials and clotting agents are delivered 2. Phagocytic migration and diapedesis - WBC squeeze into tissue from the blood stream (neutrophils then macrophages) 3. Repair of tissue - Tissue is restored
50
How do interferons work and what type of infection are they used against? Which line of defense are interferons?
- Cytokine produced by virally infected cells - Binds to uninfected nearby cells to induce antiviral proteins - Inhibits viral replication - Enhances immune response
51
How does the complement system work (in general; you don’t need to know all the details)? Which line of defense would the complement system fall under?
- Blood plasma proteins that dilate arteries and work as chemotactic agents (attract immune cells). Opsinization is binding to promote phagocytosis. Cytolysis is occurs as MAC forms
52
What are the 3 outcomes of activation of the complement system? Describe each one.
Opsonization: - C3b binds to pathogen to promote phagocytosis Cytolysis: - MAC forms creating a channel resulting in the bursting of a cell Inflammation: - Mast cell releases histamine which increases blood vessel permeability and chemotactic attraction
53
How is adaptive immunity acquired?
Infection is encountered and specific antibodies are produced to mount a specialized immune response
54
For acquired immunity, compare a primary response to a secondary response.
- A primary response takes a longer time to mount a response to an infection because it is the first time the body encounters it - Secondary response takes less time and is more robust as the body has previously encountered the infection
55
What are the two parts for the 3rd line of defense? Which one is used to fight invaders outside cells? Which one is used for viruses, some fungi, and parasites?
1. Humoral Immunity - Antibodies circulate in the body fluids 2. Cell Mediated Immunity - Fight viruses, fungi, and parasites
56
Bone marrow stem cells differentiate into either T cells or B cells. In what tissue in the body, are B cells created and mature in? In what tissue in the body, are T cells created and mature in?
- Both cells develop in either bone marrow or fetal liver - B cells mature in red bone marrow - T cells mature in the thymus
57
Which lymphocytes are responsible for humoral immunity?
B cells - Antibodies in body fluids - Bone marrow stem cells - Mature B cells are in lymphoid organs - Undergo clonal selection - B cells activated when antigen reacts with receptor -> Activation -> Plasma B cells (secretion of antibodies) and Memory B cells (Long term immunity)
58
What are the foreign molecules called that antibodies recognize and bind to?
Antigens
59
Clonal selection differentiates activated B cells into what two cell types? What is each cell type used for?
Plasma Cells: - Secrete antibodies Memory Cells: - Provide long term immunity if the antigen is encountered at a later date
60
Describe what happens during clonal selection of B cells.
1. Antigen encounters undifferentiated B cell and is selected 2. B cell grows, divides, and differentiates 3. Clones then secrete antibodies
61
Describe the structure of an antibody. What part of the antibody binds to an antigen?
- Y shaped - Consists of light chain and heavy chain - Has two antigen binding sites
62
What are the 5 functions of antibodies? Describe each one.
IgA: - Found in saliva, mucous, breast milk - Protects vs Pathogens IgD: - Part of B cell receptor - Activates Basophils and Mast cells IgE: - Protects against parasitic worms - Responsible for allergic reactions IgG: - Secreted by plasma cells in blood (80%) - Cross placenta into fetus IgM: - Can be on surface of B cell or secreted - Responsible for early stage immunity (10%)
63
How are T-dependent and T-independent antigens different?
T-dependent: - Require T cell help for B cell activation - Results in stronger and longer lasting immune response with memory T-independent: - Stimulate B cells directly - Causes weaker response with less memory (IgM)
64
Which lymphocytes are responsible for cell-mediated immunity? Do those lymphocytes combat intracellular or extracellular pathogens?
- T cells - Combat intracellular pathogens - Mature in thymus from bone marrow stem cells. Found in lymphoid tissue
65
What causes T cells to differentiate?
Differentiate when stimulated by antigen
66
What part of the T cell binds to antigens? What do T cells release after they bind to an antigen?
- T cell receptor - Release cytokines which are signaling molecules to activate other immune cells
67
Other than B cells, what are two other cell types that act as antigen presenting cells (APC)?
Macrophages Dendritic cells
68
Which type of antigen presenting cells are found in the skin, genital tract, lymph nodes, spleen, thymus, and blood?
Dendritic Cells
69
How do macrophages become activated? Which cytokine do macrophages produce?
- Activated by cytokines or ingestion of anitgenic material - Produces IL-1 which activates Th which secretes IL-2 and induces fever
70
What is the function of the cytotoxic T cells (TC; CD8+)? Which type of cells do cytotoxic T cells destroy?
- Cytolytic - Fight virally infected cells, tumor cells, and transplanted cells
71
How do cytotoxic T cells become activated? Which class of MHC (Major Histocompatibility Class) molecules are found on “self” cells?
- IL-2 and Th (t helper) cells activate Tc - Via MHC class 1 presentation
72
What is the function of the Helper T cells (TH; CD4+)? How do helper T cells become activated? Which type of “non-self” MHC molecule is used to display antigens to helper T cells?
- Commander of immune system - Produces many cytokines (signaling molecules) - Interact with macrophage - Use MHC II
73
Describe the steps of the T cell-coordinated immune response.
1. Antigen binds to BCR 2. Antigen brough into cell and broken down and displayed on MHC II 3. Th cell recognizes MHC II via TCR which activates T cell 4. Activates Th secrete IL-2 to promote proliferation and activating B cells and Tc 5. Th cells help B cells differentiate into plasma/memory cells 6. Tc recognizes antigen on MHC I and T cell is ativated 7. Tc are active (now Cytotoxic T lymphocytes) and CTL release perforins and granzymes to kill infected cells
74
What is the function of the memory T cells (TM)?
To recognize previously encountered foreign antigens
75
What is the function of the regulatory T cells (TReg)?
- Supress T cell against self - Protect intestinal bacteria - Protect fetus
76
What are the 5 types of cytokines (that are discussed in class) used in an immune response? For each one, describe which cell types produces that cytokine and the function of that cytokine.
1. IL-1: produced by macrophage; activates Th cells 2. IL-2: produced by Th; triggers T cell division, stimulates Th, Tc, increases activation and proliferation 3. B cell growth factor (IL 4): produced by Th; B cells prepare for mitosis and clonal expansion 4. B cell differentiation factor: produced by Th; B cells differentiate 5. interferon: produced by Th; magnifies immune response, blocks viral replication
77
Compare active and passive immunity.
Active - Antigen exposure results in immune response and memory development (infection or immunization) Passive - Antibodies are transfered and there is no memory (mom to baby or antitoxin
78
Describe an example for each of the following types of immunity: naturally acquired active immunity, artificially acquired active immunity, artificially acquired passive immunity, and naturally acquired passive immunity.
active: natural-infection; artificial- immunization passive: natural- mom to baby; artificial- antiserum, antitoxin, or gamma globulin
79
Describe herd immunity.
Immuntity in most of a population

Microbiology 210 (20 decks)

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