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19&27 - Coggle Diagram
19&27
Viruses
Require host cells to replicate
Not considered living organisms
Wendell Stanley
First to crystallize a virus/Tobacco Mosaic Virus
Structure
Capsid/Protein shell
capsomeres/Made of subunits
Viral Genome
DNA or RNA, single or double-stranded
Envelope
membrane derived from host cell
without envelopes
naked viruses
Viral Tegument
Protein layer between envelope and capsid
Classification
DNA Viruses
Herpesvirus, smallpox
RNA Viruses
Influenza, coronavirus
Retroviruses
use reverse transcriptase to convert RNA to DNA
Provirus/Viral DNA integrated into host genome
RNA virus uses reverse transcriptase to make DNA
DNA integrates into host genome as a provirus
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HIV
Host Interaction
Host Range
Specific species or cell types a virus can infect
Attachment
binds to host cell receptors
Entry
endocytosis or membrane fusion
Bacteriophages
Viruses that infect bacteria
Lambda phage
Vaccines
contain antigens
trigger an immune response
mRNA vaccines
Do not contain live virus; fast to produce
Viral vector vaccines
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Defense Mechanisms
Restriction Enzymes
Bacterial enzymes that cut viral DNA
CRISPR-Cas
system that stores viral DNA sequences for future defense
Prions
Infectious proteins with no nucleic acid
Cause neurodegenerative diseases
Misfold and induce misfolding in normal proteins
Replication Cycles
Lytic Cycle
Virus immediately replicates and lyses the host cell
produces many new virions
Fast and destructive
T4 bacteriophage
Attachment → Entry → Replication → Assembly → Lysis
Host cell dies, releasing viruses
Lysogenic Cycle
Dormant phase
Viral DNA integrates into host genome as a prophage
Replicates with host DNA during cell division
Can switch to lytic cycle under stress
Induction
Trigger that switches lysogenic to lytic
Temperate phage
Can choose between lytic and lysogenic
Prophage
Integrated viral DNA
Transmission
Horizontal Transmission
Virus enters through damaged tissue
Vertical Transmission
Virus passed from parent to offspring
Bacteria & Archaea
Classification & Domains
Prokaryotes/Cells w out membrane bound
Archaea/Extremophiles
Halophiles
salty environments
Thermophiles
high temperatures
Methanogens
Produce methane
Structure
Shapes of Bacteria
Coccus/spherical
Bacillus/rod-shaped
Spirillum/spiral
Clusters of Bacteria
Strepto/chains
Staphylo/clusters
Cell Wall
Made of peptidoglycan in bacteria
Gram Stain
Gram-positive
Thick peptidoglycan
Gram-negative
Thin peptidoglycan
Capsule/outer layer for protection
Slime Layer/Looser version of capsule
Endospores/resistant bacterial cells
Archaea lack peptidoglycan
Motility & Behavior
Flagella/Tail-like structures for movement
Fimbriae/Hair-like projections
Sex Pili/Used in conjugation
Taxis
Movement toward/away from stimuli
Chemotaxis/Chemical signals
Phototaxis/light
Metabolism & Oxygen Use
Autotrophs/Make their own food
Photoautotrophs/Use light
Chemoautotrophs/Use inorganic chemicals
Heterotrophs/Consume organic material
Photoheterotrophs/Use light + organic compounds
Chemoheterotrophs/Use organic chemicals
Oxygen Requirements
Obligate aerobes/Need oxygen
Obligate anaerobes/Poisoned by oxygen
Facultative anaerobes/Can survive with or without oxygen
Heterocysts
nitrogen fixation
Reproduction & Genetic Exchange
Binary Fission/Asexual reproduction
Genetic Recombination:
Transformation/Uptake of DNA from environment
Transduction/DNA transfer via viruses
Conjugation/DNA transfer via mating bridge using F factor
plasmid
F⁺ (F-positive)
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F⁻ (F-negative)
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