Microbiology Lecture- Chapter 13 Flashcards


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Viruses
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1

Viruses seen with an _________ only.

electron microscope

2

Viruses are _________ with no___________.

acellular with no membrane

3

Viruses are made of _______ and ___________.

nucleic acids and proteins-protected by a protein coat

4

Viruses have enzymes of the own and used for ____ and ______ the cell.

Entering and exiting the host cell- viral in origin

5

Known as ______ parasites

obligate parasites they have to gain entry into the cell and use the cell's machinery- outside the cell they are inert and can't do anything

6

The first virus discovered was _____________.

tobacco mosaic virus (TMV)
tobacco leaves exhibited a diseased state
- leaves showed mosaic or mottled coloration of leaves

7

Virus are measured in?

nanometers

8

Adolf Mayer attributed the disease to?

unusually small bacteria- could not be seen with a microscope

9

Dmitri Ivanowsky filtered sap of diseased plants- he assumed he could isolate and remove bacteria causing disease but plants came down with symptoms again and he assumed that the disease was caused by _____ or _______.

very small bacteria or
toxins produced by bacteria through metabolism

10

Martinus Beijerinck showed through experiments that _________ did not cause the disease.

toxins infectious particles must be reproducing.

11

True or false. Beijerinck thought that the disease would diminish but it did not. There was no dilution.

true

12

What are the viroids?

small segments of RNA- cicular

13

True or false. All viruses are infectious acellular entities

true

14

Do viroids cause human disease?

No- disease in plants only

15

True or false.Prions are even smaller than viroids and cause disease in humans and plants.

true

16

Prions are?

tiny fragments of proteins

17

Prions are in out nervous system but they are mis-folded proteins and they cause _________.

normal proteins to become misfolded and causes disease and there is no cure for a prion disease

18

Who was the first to isolate TMV?

Wendell Stanley

19
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What is this virus?

bacteriophage-it only infects bacteria in human cells only

20

How do you classify viruses since they are always mutating and changing?

You classify by the type of nucleic acid- have RNA or DNA
The structure of nucleic acid- double or single stranded RNA or DNA not typical of a normal cell
Method of replication- lytic and lysogenic
Host range:
-bacterial viruses (bacteriophage)
-most research done
-animal virses (most studied)
-plant viruses
Chemical characteristics- protein can be all the same or all different
Physical characteristics- symmetry, size etc

21

What are viruses?

infectious agents too small to be seen with a light microscope- electron only
non-filterable
not cellular
obligate intracellular parasites
contain only one type of nucleic acid

22
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A view of the different sizes of viruses

...

23

Naked virus is the _________.

simplest virus- also known as nucleo capsid- the nucleic portion and the protein coat

24
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Components of a viral particle

Nucleic acid and core
-either DNA or RNA not both
-have specific enzymes
Capsid- protein coat protects the virus from digestive enzymes or other things that can damage the virus
-determines the shape of the virus
-protects the nucleic acid
-makes up 50-80% of the biomass
-composed of protein
-subunits capsomeres
-arranged in a specific pattern
-form shape and size of virus
Other components:
-Envelopes means that the coated with another coat and that coat comes from the plasma membrane from the host cell membrane. It is acquired as it exits the cell and it goes undetected because it registers as self
-Spikes
-made of glycoprotein
-helps viral particles attach to receptors on host cell surfaces or to be released from a host cell
- key and lock- HIV virus

25
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Envelope is derived from and ________________.

the host cell and is acquired as it exits the host cell
immune system recognizes the envelope as self
contributes to overall viral shape- spherical

26

Spikes are ( see above image for picture of spikes)

spikes protrude from envelope
made of glycoprotein
allows viruses to attach to receptors on host cell
give host specificity

27

Viral morphology

The capsid gives the virus its shape

28
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What are the two types of viral morphologies?
image above of helical virus

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helical-corresponds to rod shaped viruses/ the TMV has this shape

Polyhedral- corresponds to spherically shaped viruses/ HPV has this shape- picture above is HPV

29
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What is this virus?

Ebola

30

Viral replication: two types are-

the lysogenic cycle and lytic cycle

31

The lysogenic cycle:

host cell is not destroyed replicates normally but every time it replicates it also makes a copy of the viral chromosome and self- all the daughter cells have copy of own DNA or RNA and the viral copy

32
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The lytic cycle

The host cell is destroyed
many copies made
releases 1000s of particles

33
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The lysogenic cycle

The host cell is not destroyed

34

Viral infections in animals

Two mechanisms of viral internalization
-pinocytosis-cellular drinking /bring fluids into the cells from environment that can bring in bacteria
-fusion-enveloped viruses spikes and envelopes attach to a very specific type of cell
attachment and plasma membrane invaginates and discards envelope and is recoated if necessary

35

Can only find prions after __________.

a person's death when biopsy done and they can cause serious neurological disease

36

Prion diseases that affect humans

Creutzfeldt-Jakob syndrome (CJD)
Variant CJD (vCJD)
Kuru
Gerstmann-Straussler-Scheinker syndrome
Fatal familial insomnia

37

Blue structures are protein and the pipsc is the mishapened protein that causes all normal proteins to misshape.

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