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1

Define a virus and give some general characteristics

-obligate intracellular parasites
-have a nucleic acid EITHER: RNA or DNA
-invaded in a protein capsid that surrounds the Na
-May contain am envelope around the capsid

2

Old taxonomic system

Based only on human symptoms
Some cause more than one disease
Didn't work for viruses that don't infect humans

3

New taxonomic system

Nucleic acid
How they replicate
Morphology

4

Major steps for lytic bacteriophage infection

- attachment
- penetration- injects just DNA or RNA (protein stays outside)
- biosynthesis
- Maturation: components assemble into virions
- release host cell dies!!

5

What is biosynthesis

Phase DNA directs synthesis of viral components using host stuff

6

Lysogenic pathway in bacteriophage

Steps are same as lytic except what happens with the DNA

- DNA sometime integrates with bacterial DNA
-bacteria can then replicate normally
- cell doesn't die

-sometimes virus DNA separates from bacterial DNA and continues with tthe lytic cycle (than cell dies)

7

What is a prophage

Happens In the lysogenic pathway

- bacterial viruses when some virus DNA integrates into the bacterial DNA

8

Animal virus life cycles

1. Lyric
2. Latent- cannot code for proteins
3. Persistent/slow-small amts of virus always found

9

Where do DNA and RNA replicate in animal viruses

DNA - in nucleus of host
RNA - in cytoplasm of host

10

How do animal viruses differ from bacteriophage replication

Attachment- •receptor on cell membrane
•av do not have tails
Penetration- •endocytosis
•fusion

11

Fusion

Envelope fuses with plasma membrane and releases capsid

12

Endocytosis

Plasma mem folds inward to form vesicle which virus is in loses the envelope

13

How do animal viruses release

Budding- enveloped
Lysis- non enveloped

14

Antivirus drugs that inter fear with DNA and RNA synthesis

1. Acyclovir
2. Ribavirin
3. Zidovudine (Azt)

15

Acyclovir

Inter fears with DNA and RNA synthesis

-for herpes virus
-administered orally/topically/or injected

16

Ribavirin

Stops RNA synthesis

- rotavirus treatment
- administered as aerosol

17

Zidovudine (Azt)

Inter fears with DNA and RNA synthesis

- HIV treatment
- blocks synthesis by reverse transcription
- fairly toxic

18

Enzyme inhibitors

1. Nevirapine
2. Indinavir and saquinavir

19

Nevirapine

Enzyme inhibitor

1. HIV treatment
2. Inactivates reverse transcriptase

20

Indinavir and saquinavir

Enzyme inhibitor

1. HIV treatment
2. Protease inhibitor

21

Interferon

A natural product of the immune system which cells can produce antiviral proteins

- hepatitis treatment

22

Prions

proteinaceous infectious particle

-causes rare degenerative disorders
• diseases with long incubation periods
• always progressive and fatal

23

Mode of prion in the body

Folds abnormally from normal cellular form
Causes large vacuoles in the brain (spongiform encephalopathy)

24

Transmission of prions

1. Eating cns from infected animal
2. Transplanting nerve tissue
3. Contaminated surgical instruments

25

Pathogenicity

How a microbe causes disease

26

What are the three main portals of entry for microbes

1. Mucus membranes
2. Skin
3. Parenteral route

27

Mucus membrane tract

1. Respiratory
2. Gi tract
3. Genitourinary tract

28

Genitourinary tract

STDs such as HIV, herpes, warts

29

Respiratory infection route

1. Most frequent of membrane areas
2. Easier entry point
•inhale dust
• drops of moisture

30

Gi tract infection tract

1. Microbes are acid and bile resistant
2. Enter in contaminated food or water or fingers

Ex. Dysentery, hep a, cholera

31

Skin rout of infection

1. Largest surface area of body
2. Virtually impenetrable if unbroken
3. Access through hair follicles and sweat glands

Ex. Ring worms, athlete foot

32

Parenteral rout of infection

1. Directly deposed beneath skin
•punctures
• bites
• abrasions

Ex. Gangrene, dengue fever, staph

33

What does LD50 and ID50 stand for? What is the difference between the two?

LD 50- leathal dose for 50% of host

IL 50- infectious dose for 50% of host

34

Why is adherence an important mechanism of pathogenicity? What molecules do microbes use for adherence?

They help a microbe resist or not stimulate host defenses

1. Glycoproteins
2. Lipoproteins

35

What are the four main ways that bacteria resist or not stimulate host defenses?

1. Capsules
2. Enzymes
3. Mycolic acid
4.structural proteins

36

What is the functions of capsules

1. Impairs phagocytosis
2. Prevents desiccation- tolerate any environment
3. Adherence

37

What is the function of the M protein?

Helps bac that live in the gi tract

1. Cell surface and fimbrae
2. Acid and heat resistant
3. Adherence
4. Prevents phagocytosis

Produced by strep pyrogens

38

What is mycolic acid and what is its function

1. Waxy lipid found in cell wall
2. Resistant to phagocytosic digestion

39

What is an exoenzyme?

Secreted from metabolism of bacteria to outside of the cell

40

What is a Leukocidin? What is a producer

Exoenzyme

1. Destroy white blood cells
2. Produce by gm+ cocci

41

Hemolysis and producer

Exoenzyme

1.. Lyse red blood cells and some Lyse white blood
2. Produced by gm+ cocci and clostridium perfrigenes

42

Coagulase and producer

Exoenzyme

1. Clots blood
2. Prevents access to bacteria from WBC by forming a barrier
3. Produced by staph sp.

43

Kinase and producer?

Exoenzyme

1. Dissolves clots that body forms to isolate infection
2. Keeps body from trapping bac
3. Produced by gm+ cocci

44

Hyaluronidase and Collagenas and producer

Exoenzymes

1. Breaks down connective tissue which helps bac spread
2, blackens tissue
3. Produced by clostridium perfrigens (c) and streptococci (h)

45

What are invasions

Proteins which rearrange cytoskeleton to enter cell
Produce actin baskets to cause mem ruffling

46

What were the main substances we talked about which cause host damage?

1. Direct damage by killing cells
2. Toxins

47

What are the major differences between exotoxins and endotoxins?

Exotoxins: are produced by living cells are are disease specific

Endotoxins: toxin released when bac dies

48

6 exotoxins

1. Diphtheria toxin
2. Erythrogenic toxin
3. Botulism toxin
4. Tetanus toxin
5. Vibrio toxin
6. Staphylococcus enterotoxins

49

Diphtheria toxin

Cytotoxic exotoxin

1. Inhibits protein synthesis

Ex. Corynebacterium diphteriae

50

Erythrogenic toxin

Cytotoxin Exotoxin

1. Damage blood capillaries which causes skin rash

Ex. Strep. Pyrogens or scarlet fever

51

Botulism toxin

Neurotoxin exotoxin

1. Prevents transmission of impulses from nerve to muscle (flaccid paralysis)

Ex. Clostridium botulinum (food poisoning)

52

Tetanus toxin

Neurotoxin exotoxin

1. Blocks the relaxation pathway of muscle contraction

Ex. Clostridium tetani (lock jaw)

53

Vibrio enterotoxin

enterotoxin exotoxin

1. Causes the discharge of fluids and electrolytes in the small intestine

Ex. Vibrio cholerae (severe diarrhea)

54

Staphylococcus enterotoxin

enterotoxin exotoxin

1. Similar to vibrio enterotoxin and toxic shock syndrome

Ex. Staphylococcus aureus

55

What is the major endotoxin? What portion of this molecule?

Lps in gm- as part of outer membrane

Lipid A proration is the endotoxin

Exposed to body when gm- dies

56

What are four responses of the body to endotoxins?

1. Immune response: release of cytotoxins
2. Activation of blood clotting (blocks Capps)
3. Fever (inhibit bac growth)(aspirin reduces f)
4. Septic shock

57

What is the end result of septic shock?

1. Loss of Bp so yes, death

Loss of bp I'd due to macrophages releasing tnf which increases Capp permeability which fluid then enters causing a drop of bp

58

What is a cytopathic effect

Visible effects of a viral infection to cells

1. Change in growth of host cell
2. Causes lysosomes to dump digestive enzymes into cell
3. Inclusion bodies form (viral gs in cytoplasm or n)
4. Syncytium form (multinuclear cells)
5, changes in host cell function
6. Interferons produced by infected cells
7. Antigens change cell surface
8. Activation of oncogenes
9. Loss of control inhibition

59

What is the cause of AIDS?

HIV

60

List some characteristics and some information about the structure of the virus?

HIV is a RNA virus

Retrovirus

2 identical strands of RNA

Reverse transcriptase

Envelope

61

How is the virus transmitted?

Most common are sex any way with infected person

Shared needles

HIV infected mothers giving vaginal birth to babies

HIV breast feeding

62

List some information about the virus life cycle (steps it takes to make more viruses).

1. Virus attaches to cd4 receptor- helper T cells
2. Corecepter also needed (cd 4/5)
3. Capsid enters cell by fusion
4. Uncoating of capsid
5. DNA May produce HIV bud

63

What are some prevention/treatment methods used for the disease?

Put a condom on yo dick!!

Don't do drugs

Don't be a whore

Or just don't have sex

64

Define bacteriophage

Viruses that infect bacteria