Summary

Summary CSB351 Term Test 1 Review

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Course
CSB351 (CSB351)

Institution
University Of Toronto (U Of T )

Complete and in-depth Term Test 1 Notes for CSB351 for EXAM prep. Kevin has combined notes from his peers and his own work to provide the most complete and comprehensive study guide for all types of students. He has achieved an overall cumulative GPA of 3.95 during his undergrad at the University o...

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Uploaded on June 10, 2018
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CSB351

Lecture 1 – Discovery and Nature of Viruses
 So what’s a virus?
o Lwof
 Strictly intracellular
 Potentially pathogenic
 Infectious
 Only one type of nucleic acid
 Multiply only in that one type of nucleic acid
 Cannot grow or perform binary fssion
 No Lipmann system
 Cannot produce ATP/ribosomes
 No energy, prety much
o Someone else
 Tiny submicroscopic particle
 Can multiply in living cells, inducing illness
 Can atack everything
o Goodheart
 Genetic material in a protective coating
 No metabolism, no mobility, no response, no growth
 Can be considered “alive” solely due to ability to transmit genetic code
 With possibility of mutation
o Regardless…
 During reproduction, virus inserts itself into host cell’s machinery
 Genes of virus cause cell to either produce more virus or to adapt to
further serve the virus
 When ready, virus leaves either through budding or through splitng
cell open
 Viral properties
o Smaller than life
o Simpler than life
 Only a few genes worth of nucleic acid plus a shell of protein, in general
o Cannot multiply in vitro
 Requires life in order to reproduce
 Hijacks host’s nucleus, mitochondria, ribosome, etc.
 Life cycle
o Virus enters cell
 Receptor recognizes virus and lets it in
 Virus ataches to cell membrane and gets involuted
 Vesicle opens up, then viral capsid
o Viral replication

,  Viral nucleic acids converted, somehow, to mRNA
 mRNA translated, viral proteins made
 Capsid made afer viral nucleic acids, since capsid is marker to stop
replication
o Exit
 Lysis
 Enough viral nucleic acids packaged into capsids provides signal to get
show on the road
 Cell bursts open and new virus particles pop out
 Budding
 Same signal, except it’s to go to the plasma membrane and bud of
 Glycoproteins added as necessary to lipid membrane
 New virus particles bud of

Lecture 2 – Composition of Viruses
 Nucleic acids
o RNA or DNA, but not both
 Ribose vs deoxyribose
 Phosphate backbone is very charged (negativee
 Glycosidic (covalente bonds between NH group of acid (pos. 9 of purine/1 of
pyrimidinee to 1’ of sugar
 Phosphates link to sugars at 3’ and 5’
 3’ and 5’ ends of DNA
o Covered with protein
o Some viruses contain lipids and carbohydrates
 Enveloped, for example
o Nucleic acids and proteins are not covalently linked, but rather maintained by non-
covalent interactions
 Hydrogen bonds, charge, hydrophobicity, etc.
 Allows for easy uncoating
o Modifed nucleic acids
 Some viruses have modifed nucleic acids
 m7G
 Guanine, but with methylated cap
o 5’-5’ link, which is unusual
 Methylated cap marks RNA to be translated
o Cap-binding enzyme fnds it and brings it over to ribosome
 Most tRNA have caps, some don’t
o Poliovirus, for one
 Prevents degradation by exonucleases, promotes translation of mRNA
and +ssRNA
o Nucleic acid synthesis

,  RNA polymerase binds to double stranded DNA
 Helicase splits open double strands
 RNA polymerase continues along one strand, adding complementary
nucleotides
o Synthesis enzymes
 Polymerases
 Add nucleotides to 3’ end of a strand of DNA/RNA
 Sequence determined by following template strand
o Add complementary to template strand
 Some RNA polymerases do not require primer
o Primers are small segments of DNA/RNA that are hybridized to
the template strand
o Polymerase latches onto primer to fnd out where it’s going
 DNA polymerases require primers
 Most viruses code for their own polymerases
 Classes of polymerase
 DNA-dependent RNA polymerase (DdRpe
o Take DNA template, write mRNA
 Nuclear, mostly
o Only pox viruses and other huge viruses code for this
 Most cells use cellular DNA-dependent RNA polymerase
 Those go to nucleus
 Pox doesn’t need to go to nucleus, it has its own DNA
and its own DdRp
 RNA-dependent RNA polymerase (RdRpe
o Take RNA template, make RNA
 Cytoplasmic
o Encoded by RNA viruses so they can replicate
 +ssRNA make their own in cytoplasm
 -ssRNA, dsRNA bring their own in capsid
 RNA-dependent DNA polymerase (RdDp/RTe
o Take RNA template, make DNA
o Retroviruses
 This is reverse transcriptase
o Modifcation enzymes
 Methylase
 Adds methyl groups to bases
 Most mRNA, many +ssRNA viruses have methylated 5’ caps
 Nuclease
 Cleave the individual nucleotides in a stretch of acids
 Endonuclease
o From the middle

,  Exonuclease
o From the end
 Ribonuclease
o RNA
 Deoxynuclease
o DNA
 Ligase
 Join two stretches of nucleic acids together through covalent bonding
o Hydrolysis
 RNA and DNA ligases
 Shapes
o Helical
 Rod-shaped capsid with nucleic acid embedded inside wall of rod
 Hollow
o Icosahedral
 20-sided ball of repeated subunits
 “Spherical”
o Enveloped
 Lipid envelope surrounding viral nucleic acids
o Bacteriophage
 Round ball on top of helical rod, plus “legs”

Lecture 3 – Composition: Proteins, Lipids, Glycoproteins
 Proteins
o Function
 Structure
 Capsid, for protection of viral innards
 Enzyme
 Facilitate reactions
 Polymerase, integrase, etc.
 Signaling
 Receptors and receptor binding molecules
 Movement
 Plant viruses require movement protein
 Antigenic
 Viruses (viral proteinse induce production of antibodies
 Pathology
 Capsid protein itself can be what induces viral symptoms in plants
 Virus takes structural with it when it leaves cell, leaves behind enzymes
(sometimese
 -ssRNA, dsRNA package RdRp into daughters
o Structure

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