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Microbiology > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

Some mutations cause diseases. Cystic fibrosis is an example. Describe it.

A

The mutation is in the cystic fibrosis transmembrane regulator (CFTR) gene. The balance of chloride in the body isn’t restricted. Symptoms include difficulty breathing, recurrent lung infections, digestive, and reproductive issues.

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2
Q

Mutations cause Huntington’s disease. Describe the condition.

A
  • genetically programmed degeneration of neurons in certain areas of the brain
  • the degeneration causes uncontrolled movements, loss of intellectual faculties and emotional disturbance
  • typical onset is in the 30s and progresses 10 to 20 years until death
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3
Q

Sickle cell anemia is caused by mutations. Describe the condition.

A
  • condition in which there aren’t enough healthy red blood cells to carry adequate oxygen
  • irregular shaped red blood cells become rigid and sticky
  • become stuck in small blood vessels
  • can cause hemolytic anemia
  • sickled RBCs block capillaries and interfere with blood flow to organs
  • symptoms: pain in joints, fatigue, inability to make concentrated urine, susceptibility to infection, developmental delays, shortness of breath, vision problems
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4
Q

How was virus defined by a Nobel Prize winner, Peter Medawar?

A

“a piece of bad news wrapped up in protein”

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5
Q

How many strains of virus are there?

A

Over 320,000 that affect mammals

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6
Q

Describe the structure of a virus.

A
  • no cell nucleus
  • no organelles
  • no cytoplasm
  • too small to be seen with a light microscope
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7
Q

Where do virus replicate?

A

Can only replicate inside a living host cell (obligate intracellular parasite). Shares this distinction with chlamydias and rickettsias (living organisms).

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8
Q

What is an obligate intracellular parasite?

A

A virus that has no means to produce energy and contains a few enzymes at most

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9
Q

What do virus depend on?

A

Strict dependence on host cell structural and metabolic components

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10
Q

How do virus replicate?

A
  • carried out by the host cell machinery

* multiple copies of the viral genome and viral proteins (enzymes and structural) are synthesized

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11
Q

Which is larger, yeast cells or bacterial cells?

A

yeast cells are larger (7 um) while bacterial cells are a max of 2 um.

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12
Q

What is a virion?

A

It is a complete extracellular structure that transmits the infection

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13
Q

What is the range of clinically relevant virus sizes?

A

32 nm (poliovirus) to 300 nm (poxvirus)

Viruses vary in volume and instructors from relatively simple to very complex.

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14
Q

What are the two main parts of a virus?

A
  • delivery system

* payload

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15
Q

What does the payload contain?

A
  • the genome and enzymes necessary to initiate the first steps in virus replication
  • material for sustainability and perpetuation (inheritance)
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16
Q

What does the delivery system do? What does it contain?

A
  • protects the payload against degradation in the environment
  • contains structures used to bind to target cells in the host
  • target specificity and binding
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17
Q

What is a capsid?

A

It is the protein coat surrounding the genome of a virus.

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18
Q

What are the two common shapes of a capsid?

A
  • icosahedral

* helical

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19
Q

What is a capsomere?

A

Protein subunits that assembled together to form the capsid–make up the capsid.

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20
Q

What are viruses without an envelope called?

A

non-enveloped viruses

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21
Q

What have target organ specificity?

A

capsomeres

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22
Q

What are enveloped viruses?

A

Viruses that have an envelope that surrounds the nucleocapsid

23
Q

What is the viral envelope sensitive to and made of?

A
  • sensitive to acid and bile

* composed of virus specific proteins, lipids and carbs derived from host cell and organelle membranes

24
Q

What do virus specific glycoproteins do?

A
  • agglutinate red blood cells (hemagglutination) by binding to receptors on the erythrocyte surface
  • determines target organ specificity
  • entry routes (GI vs respiratory)
25
Q

What are the most common DNA viruses?

A
  • double stranded DNA linear

* circular genomes

26
Q

What is the less common DNA virus?

A

single stranded linear genome

27
Q

RNA virus account for what percentage of all viruses? What type of error rate does RNA replication mutation have?

A
  • 70% of viruses

* High error rate enzymes for RNA replication mutation rate–great adaptability

28
Q

There are 3 types of of RNA viruses. What are they?

A
  • double stranded
  • single genome or segmented
  • single stranded
29
Q

Describe single stranded RNA.

A
  • sense or polarity is positive or negative
  • the sense strand is positive and can function as mRNA
  • the antisense strand is negative and can not function as mRNA
  • the antisense strand is requires a vision associated polymerase activity to make a copy for use as a mRNA
30
Q

The class Rhabdovirus causes what type of disease?

A

Rabies

31
Q

What are the stages of viral infections?

A
  1. Encounter
  2. Entry
  3. Spread
  4. Multiplication (host specific intracellular replication)
  5. Damage
32
Q

What should we know about gate keepers?

A

1-3: NK cells, IFNs, humoral immunity

4-5: humoral, cell mediated immunity

33
Q

How can infection be acquired?

A
  • from other humans

* from the environment

34
Q

What are the direct contact routes for virus?

A
  • contact with lesions or sexual (per mucosal)

* vertical transmission (pregnant woman to fetus)

35
Q

Other than direct, what are the other types of transmission?

A
  • respiratory: aerosols, airborne, or droplets
  • gastrointestinal: fecal-oral causes contamination by ingestion
  • percutaneous: injection drug abuse, needlesticks (blood or body fluid)
36
Q

What are the steps of transmission?

A
  • attachment
  • penetration
  • uncoating
  • replication
  • transcription
  • translation
  • assembly (maturation)
  • release
37
Q

Where do most DNA virus replicate?

A

in the nucleus

38
Q

Where do most RNA virus replicate?

A

in the cytosol (except influenza and retrovirus)

39
Q

What is attachment?

A

spikes attach to the cell either going in by penetration (inject DNA into cell) or swallowed by endocytosis. It involves linking of specific vision protein (anti-receptor) to cognate ligand on cell surface (receptor).

40
Q

Cells lacking the specific receptor are not susceptible to what?

A

viral infection

41
Q

Attachment is dependent on what?

A

Upon the affinity of the viral anti-receptor for its host target receptor

42
Q

What happens during entry of a virus?

A

*the viral capsid permits delivery of the genome into the cell

43
Q

What does the genome in the capsid encode?

A

They encode proteins that permit the virus to control the cell and replicate.

44
Q

What is a clathrin coated pit?

A

A cavelike polyhedral molecular arrangement of protein that forms on the cytoplasmic side of a cell’s plasma membrane and coats the endocytotic vesicles which bud off from the membrane.

45
Q

smallpox

A

poxvirus (dsDNA)

46
Q

chicken pox

A

herpesvirus (dsDNA)

47
Q

herpes

A

herpesvirus (dsDNA)

48
Q

mumps

A

paramyxovirus (ssRNA template for mRNA)

49
Q

polio

A

picornavirus (ssRNA serving as mRNA)

50
Q

influenza

A

orthomyxovirus (ssRNA template for mRNA)

51
Q

hepatitis

A

hepadnavirus (dsDNA with RNA intermediate template for DNA synthesis)

52
Q

west nile

A

flavivirus

53
Q

rabies

A

rhabdovirus

54
Q

You realize that you are sick with a virus transmitted via the fecal-oral route. What type of virus are you likely infected with?

A

enteric adenovirus

Microbiology (10 decks)

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