M4 - Virology

Question 1

Characteristics of a virus

Answer 1

• Intracellular parasite
– Cannot replicate outside a living cell
– Large inert macromolecules
• Possess only one kind of nucleic acid: DNA or RNA
• Limited amount of genetic material: ~3-200 genes
• cannot code for energy production due to not enough genetic info
• no ribosomes
• not grow but replicate to increase the number
• Viral nucleic acid and viral protein synthesis occur separately: come together during maturation.
• Lipids and carbohydrates are acquired from the host cell (not coded for by viral genome)

Question 2

Composition of a virus

Answer 2

a nucleic acid genome (RNA or DNA) + protein

Question 3

Virus proteins are coded by …

Answer 3

viral genome or from host

Question 4

particle (virion)

Answer 4

病毒顆粒（病毒粒子）

Question 5

penetration

Answer 5

滲透

Question 6

polymerases

Answer 6

聚合酶

Question 7

helicases

Answer 7

解旋酶

Question 8

proteases

Answer 8

蛋白酶

Question 9

Structural proteins

Answer 9

part of the virus particle (virion) and wrapping around the core of viruses

Question 10

Functions of structural proteins

Answer 10

cell attachment and penetration & protection

Question 11

Location & functions of Non-structural proteins

Answer 11

most not found in virion

– replication(polymerases,helicases)
– virus assembly and release (proteases)

Question 12

Nucleocapsid

Answer 12

核衣殼 = capsid(protein shell surrounding viral genome) + genome

Question 13

Capsid

Answer 13

衣殼
protein shell surrounding viral genome

Question 14

capsomer

Answer 14

衣殼粒a kind of structural proteins
Many capsomers make capsids

Question 15

Icosahedral

Answer 15

二十面體

Question 16

spherical

Answer 16

球體

Question 17

Helical Nucleocapsids

Answer 17

螺旋核衣殼

Question 18

Rod-shaped

Answer 18

桿狀

Question 19

naked viruses

Answer 19

Viruses composed only of nucleic acid and protein

Question 20

enveloped viruses

Answer 20

Viruses that acquire an outer layer of membrane from the host during replication

Question 21

Feature of naked virus

Answer 21

• very stable in the environment
• nucleic acid “encased” in protein

Question 22

Feature of Enveloped viruses

Answer 22

• more fragile 脆弱
• more susceptible to inactivation because of lipid content

Question 23

naked helical viruses only found in…

Answer 23

plant and bacterial viruses

Question 24

Complex Viruses

Answer 24

Large viruses with complex structure

Question 25

How do viruses acquire an envelope?

Answer 25

The virus acquires the envelope as it matures and buds through the cell membrane

Question 26

What factors determine the structure of a virus

Answer 26

1. Types of viruses 2. Type of Nucleic Acid: DNA or RNA 3. Capsid protein: The composition and arrangement of the capsid protein affect the appearance of the virus. 4. Have envelope or not

Question 27

Stages of replication

Answer 27

1. absorption/attachment 2. Penetration 3. uncoating 4. replication 5. release/maturation

Question 28

Virus attachment sites

Answer 28

Enveloped viruses: spike or peplomers Naked viruses: anywhere

Question 29

spike

Answer 29

尖峰

Question 30

peplomers

Answer 30

聚合物

Question 31

The way of Attachment

Answer 31

– physical complementarity between virus and receptor – specific interaction (most viruses can only infect some cell types)

Question 32

PENETRATION

Answer 32

內吞作用 virus is engulfed into cytoplasmic vacuole

Question 33

The ways of penetration

Answer 33

1. Endocytosis 2. Membrane fusion: only enveloped viruses 3. Direct entry: some naked viruses

Question 34

The ways of penetration for naked viruses

Answer 34

1. direct entry: The nucleocapsid undergoes molecular rearrangement allowing viral genome to enter the cell. 2. Exosomes: Naked viruses are excreted from infected cells in exosomes and enter new cells in membrane-bound particles

Question 35

Un-coating

Answer 35

allows release of the genome into the cytoplasm - Often spontaneous自發性的

Question 36

Synthesis of viral protein and nucleic acid for DNA viruses

Answer 36

Replicate in the cell nucleus because all DNA replicative enzymes are found in the nucleus

Question 37

Synthesis of viral protein and nucleic acid for RNA viruses

Answer 37

Generally replicating in the cytoplasm RNA viruses code for replicative enzymes (proteins) but need polyribosomes to translate them from mRNA

Question 38

Replication of negative (-) strand genome

Answer 38

1. Negative strand genomic RNA released into the cytoplasm 2. The replicase enzymes are brought into the cell as part of the virion 3. Negative (-) strand RNA must first serve as a template to make complementary positive (+) strand RNA to translate viral proteins.

Question 39

Virus maturation and release

Answer 39

simple viruses: self-assembly complex viruses: require various stages

Question 40

Maturation and release of viruses for naked viruses

Answer 40

Mainly, accumulate累積 in cell and release progeny子代 virus suddenly through cell bursted破裂 but some progeny viruses are secreted gradually from intact cell in exosomes

Question 41

exosomes

Answer 41

外泌體

Question 42

progeny

Answer 42

子代

Question 43

Maturation and release of viruses for Enveloped viruses

Answer 43

bud through cell membrane – released gradually

Question 44

Three types of targets for Antiviral Agents

Answer 44

Protein synthesis Cellular enzymes for DNA replication (for DNA viruses) Cellular energy to drive synthesis and enzyme reactions

Question 45

necrosis

Answer 45

壞死：cell death by rupture of cell during virus release

Question 46

apoptosis

Answer 46

細胞凋亡cell commits suicide in response to infection

Question 47

Immunopathology

Answer 47

免疫病理學

Question 48

What causes the symptoms of virus infection?

Answer 48

1) Damage to cells due to virus replication: necrosis壞死, apoptosis細胞凋零 ＆ infected cell loses function 2) Damage due to the host response to infection: Immunopathology, fever, inflammation

Question 49

pathogenesis

Answer 49

發病機制

Question 50

HOST factors which modify viral pathogenesis

Answer 50

* Age * Genetics * Metabolic state * “Altered” immune responses: genetically determined, consequence of infection & iatrogenically (therapeutically)

Question 51

iatrogenically

Answer 51

醫源性

Question 52

Routes of virus entry

Answer 52

* skin * respiratory tract * gastrointestinal tract * genitourinary tract * conjunctiva

Question 53

gastrointestinal tract

Answer 53

胃腸道

Question 54

genitourinary tract

Answer 54

泌尿生殖道

Question 55

conjunctiva

Answer 55

結膜

Question 56

how virus get into host through skin

Answer 56

* mechanical trauma * by injection * by the bite of an infected sth

Question 57

how virus get into host through Genitourinary Tract

Answer 57

Tears or abrasions擦傷

Question 58

abrasions

Answer 58

擦傷