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VIRUSES HAVE TO THE CAPABILITY TO INFECT...
EVERY CELLULAR ORGANISM
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WHAT DOES " FILTERABLE VIRUSES" MEAN
- VIRUSES THAT ARE CAPABLE OF PASSING THROUGH FILTERS MEANT TO TRAP BACTERIA
- A CELL FREE FLUID COULD CONTAIN AGENTS THAT COULD CAUSE INFECTION
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WHAT IS THE ROLE THAT VIRUSES HAVE PLAYED IN THE EVOLUTION OF ALL ORGANISMS
- INFECT CELLS AND INFLUENCE THEIR GENETIC MAKEUP
- SHAPE THE WAY CELLS, TISSUES, BACTERIA, PLANTS AND ANIMALS HAVE EVOLVED
- 10% OF HUMAN GENOME CONSISTS OF VIRAL SEQUENCES
- 10-20% OF BACTERIAL DNA CONSISTS OF VIRAL SEQUENCES
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WHY ARE VIRUSES OBLIGATE INTRACELLULAR PARASITES
VIRUSES CAN'T MULTIPLY UNLESS THEY INVADE A SPECIFIC HOST CELL & INSTRUCT ITS GENETIC & METABOLIC MACHINERY TO MAKE AND RELEASE NEW VIRUSES
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WHAT CHARACTERISTICS ARE USED TO NAME VIRUSES
- HOST AND DISEASE THEY CAUSE
- STRUCTURE
- CHEMICAL COMPOSITION
- SIMILARITIES IN GENETIC MAKEUP
- TAXONOMY
- 3 ORDERS
- 73 FAMILIES
- 283 GENERA
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HOW BIG ARE VIRUSES COMPARED TO OTHER ORGANISMS
- SMALLEST INFECTIOUS AGENT 20-800NM
- NO RESEMBLANCE TO CELLS LACK PROTEIN SYNTHESIZING MACHINERY FOUND IN CELLS
- ONLY HAVE PARTS NEEDED TO INVADE HOST
- - EXTERNAL COATING
- - SOMETIMES 1 OR 2 ENZYMES
- - CORE CONTAINING 1 OR MORE NUCLEIC ACIDS (RNA OR DNA)
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STRUCTURE AND FUNCTION OF VIRAL CAPSIDS
- PROTEIN SHELL THAT SURROUNDS THE NUCLEIC ACID
- NUCLEOCAPSID - CAPSID AND NUCLEIC ACID TOGETHER
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THREE DIFFERENT TYPES OF CAPSIDS
- HELLICAL
- ICOSAHEDRAL
- COMPLEX
- COMPOSED OF IDENTICAL PROTEIN SUBUNITS CALLED CAPSOMERES
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DISTINGUISH BETWEEN ENVELOPED VIRUS & NAKED VIRUS
- ENVELOPED VIRUS - TAKE A BIT OF THE CELL MEMBRANE WHEN THEY ARE RELEASED FROM A HOST CELL
- CAN BUD FROM - CELL MEMBRANE, NUCLEAR ENVELOPE, ENDOPLASMIC RETICULUM.
- THESE ARE PPLEOMORPHIC
- NAKED ENVELOPE - VIRUSES THAT CONSIST OF ONLY NUCLEOCAPSID.
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UNDERSTAND THE IMPORTANCE OF VIRAL SURFACE PROTEINS OR SPIKES
- SURFACE PROTEINS/ SPIKES
- CAN BE FOUND ON NAKED OR ENVELOPED VIRUSES
- PROJECT FROM NUCLEOCAPSID OR THE ENVELOPE
- ALLOWS VIRUSES TO DOCK WITH HOST CELLS
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DESCRIBE THE 3 DIFFERENT TYPES OF OF CAPSIDS
- HELICAL CAPSID - ROD SHAPED CAPSOMER THAT BOND TOGETHER
- ICOSAHEDRON - THREE DIMENSIONAL, 20 SIDED FIGURE
- COMPLEX - NON SYMMETRICAL SHAPES, MULTIPLE TYPES OF PROTEINS
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WHAT ARE THE DIFFERENT COMPOSITIONS OR VIRAL NUCLEIC ACID
- VIRUSES CONTAIN EITHER DNA OR RNA (NEVER BOTH)
- VIRUSES - COMPACT NECESSARY INSTRUCTIONAL REPLICATION GENES (SMALL COMPARED TO GENES OF HOSTS CELL)
- CONTAIN ONLY GENES NEEDED TO INVADE HOST
- DNA VIRUSES ARE EITHER SINGLE STRANDED (SS) OR DOUBLE STRANDED (DS) LINEAR OR CIRCULAR
- + SENSE RNA: SS RNA GENOME READY FOR IMMEDIATE TRANSLATION
- SEGMENTED RNA - INDIVIDUAL GENES EXIST ON SEPARATE PLACES
- - SENSE RNA: SS RNA HAVE TO BE CONVERTED INTO PROPER FORM TO MADE INTO PROTEIN
- RETROVIRUS - CARRY THEIR OWN ENZYMES TO CREATE RNA OR DNA
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WHAT ARE THE DIFFERENT RELEASE STRATEGIES FOR NAKED VS ENVELOPED VIRUSES
- ENVELOPED ARE LIBERATED BY BUDDING FROM THE MEMBRANE OF THE CYTOPLASM, NUCLEUS & E.R. OR VESICLE
- DURING THE PROCESS THE NUCLEOCAPSID BINDS TO THE MEMBRANE, WHICH CURVES COMPLETELY AROUND IT AND FORMS A SMALL POUCH
- NAKED - REACH MATURATION IN THE CELLS NUCLEUS OR CYTOPLASM AND ARE RELEASED WHEN CELL LYSES (RUPTURES)
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WHAT IS THE REPLICATION STRATEGY FOR RNA VIRUSES VS. DNA VIRUSES
- RNA - REPLICATED AND ASSEMBLED IN CYTOPLASM
- DNA - ENTER THE HOST CELLS NUCLEUS AND ARE REPLICATED AND ASSEMBLED THERE
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RETROVIRUSES TURN THEIR RNA GENOMES INTO DNA
STEP IS ACCOMPLISHED BY A VIRAL ENZYME CALLED REVERSE TRANSCRIPTASE AND HAS IMPORTANT IMPLICATIONS IN INFECTIONS WITH THESE VIRUSES
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GENERAL PHASES OF ANIMAL VIRUS
- ADSORPTION - VIRUS CAN INVADE HOST ONLY THROUGH MAKING AN EXACT FIT WITH SPECIFIC HOST MOLECULES
- PENETRATION - FLEXIBLE CELL MEMBRANE OF THE HOST CELL IS PENETRATED BY THE WHOLE VIRUS OR ITS NUCLEIC ACID
- ENDOCYTOSIS - ENTIRE VIRUS IS ENGULFED BY THE CELL ENVELOPED IN A VACUOLE
- UNCOATING - ENZYMES IN VACUOLE DISSOLVE THE ENVELOPE AND CAPSID. VIRUS FUSES WITH THE WALL OF VESICLE
- - VIRAL NUCLEIC ACID RELEASED INTO CYTOPLASM
- - DIRECT FUSION - ENVELOPE MERGES DIRECTLY W/ CELL MEMBRANE
- SYNTHESIS REPLICATION & PROTEIN PRODUCTION -
- IN GENERAL DNA VIRUSES ENTER THE HOST CELLS NUCLEUS ARE REPLICATED & ASSEMBLED INTO CYTOPLASM
- ASSEMBLY - PUTS TOGETHER THE NEW VIRUS USING THE "PARTS" MANUFACTURED IN THE SYNTHESIS PROCESS: NEW CAPSID AND NEW NUCLEIC ACID
- RELEASE - # OF VIRUSES RELEASED BY THE INFECTED CELL IS VARIABLE CONTROLLED BY HEALTH OF HOST CELL AND SIZE OF VIRUS
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PERSISTENT AND TRANSFORMING INFECTIONS
- PERSISTENT - CAN LAST FROM A FEW WEEKS TO THE REMAINDER OF A HOST'S LIFE
- - CELL HARBORS VIRUS
- - NOT IMMEDIATELY LYSED
- - CAN REMAIN LATENT IN THE CYTOPLASM
- TRANSFORMING - ( USED TO DESCRIBE CANCER CELLS )
- - INCREASED RATE OF GROWTH
- - ALTERATIONS IN CHROMOSOMES
- - CHANGES IN CELLS
- - CAPACITY TO DIVIDE FOR INFINITE PERIOD
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LYSOGENIC VS. LYTIC VIRUSES
- LYSOGENIC - (SILENT VIRUS INFECT)
- - CONDITION IN WHICH HOST CHROMOSOME CARRIES VIRAL DNA BECAUSE VIRAL PARTICLES ARE NOT PRODUCED THE BACTERIA CELLS CARRYING TEMPERATE PHAGE DO NOT LYSE
- LYTIC - WHEN A BACTERIUM ACQUIRES A NEW TRAIT FROM ITS TEMPERATE PHAGE. BAD NEWS FOR HOST
- - T EVEN BACTERIOPHAGES LYSE BACTERIAL CELL
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WHAT ARE HOST RANGE AND TROPISMS AND HOW DOES IT RELATES TO A VIRUS
- HOST RANGE - LIMITED RANGE OF CELLS THAT A VIRUS CAN INFECT.
- - IE: HEP B - LIVER CELLS IN HUMANS
- - CELLS THAT LACK COMPATIBLE VIRUS RECEPTORS ARE RESISTANT TO ADSORPTION & INVASION BY THAT VIRUS
- TROPISM - SPECIFICITIES OF VIRUSES FOR CERTAIN TISSUE
- - WHY VIRUSES CAN RESIDE IN CERTAIN PLACES
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DESCRIBE PENETRATION VIA ENDOCYTOSIS VS. DIRECT ENVELOPE INFUSION
- PENETRATION VIA ENDOCYTOSIS - ENTIRE VIRUS IS ENGULFED BY THE CELL AND ENCLOSED IN A VACUOLE OR VESICLE
- UNCOATING - ENZYMES IN THE VACUOLE DISSOLVE THE ENVELOPE AND CAPSID
- - VIRUS FUSSES WITH THE WALL OF THE VESCICLE
- - VIRAL NUCLEIC ACID IS RELEASED INTO THE CYTOPLASM
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