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CHAPTER 19 AND 27 - Coggle Diagram
CHAPTER 19 AND 27
CHAPTER 19
WHAT IS A VIRUS
infectious particle
genes inside protein coat
not a cell
no metabolism
cannot reproduce alone
exists between living and non living
example: tobacco mosaic virus (TMV)
STRUCTURE OF VIRUSES
genome
DNA OR RNA
single stranded or double stranded
linear or circular
capsid
protein shell
made of capsomeres
shapes
helical
icosahedral
envelope
some viruses
from host membrane
contains viral + host molecules
has glycoproteins for attacthment
bacteriophages (phages)
infect bacteria
head = DNA
tall injects DNA
VIRAL REPLICATION
obligate intracellular parasites
can only replicate in host cell
host range = limited hosts infected
general steps
virus enters cell
host makes viral proteins
viral genome copied
parts self-assemble
PHAGE REPLICATION CYCLES
LYTIC CYCLE
viral DNA enters cell
new phages made
host cell lyses (burst)
release viruses
virulent phage
LYSOGENIC CYCLE
viral DNA integrates into host DNA
intergrated DNA = prophage
copied when host divides
environmental signal - switches to lytic
temperate phage (lambda)
BACTERIAL DEFENSES
receptor mutations
restriction enzymes
cut foreign DNA
host DNA protected by methylation
CRISPR-cas system
stores viral DNA sequences
produces RNA guides
cas proteins cut viral DNA
provides immunity to repeat infections
ANIMAL VIRUSES
classified by
dna or rna genome
single or double stranded
envelope present or absent
enveloped virus
envelope from host membrane
glycoproteins bind host receptors
retoviruses
rna genome
use reverse transcriptase
rna - dna
integrated dna = provirus
example: HOV - AIDS
VIRAL DISEASES IN ANIMALS
damage cells directly
trigger toxin release
envelope proteins may be toxic
vaccines
harmless pathogen forms
prevent disease
antibiotics do NOT work on viruses
antiviral drugs
inhibit replicartion
treat, not cure
EMERGING VIRAL DISEASES
newly appearing or spreading viruses
causes
viral mutation
animal - human transfer
environmental change
examples
hiv
ebola
zika
influenza A
influenza
high mutation rate
gene reassortment
pandemic possible
H1N1, H5N1 examples
VIRAL DISEASES IN PLANTS
causes
stunted growth
leaf spots
damaged roots/flowers
mostly rna virus
capsids
helical
icosahedral
transmission
horizontal (cell demage)
vertical (parent - offspring)
PRIONS
infectious proteins
no nucleic acid
misfiled proteins
cause brain diseases
extremely stable
spread by food
convert normal proteins into prions
examples
mad cow disease
scrapie
creutzfeldt-jakob diseas
CHAPTER 27
PROKARYOTIC STRUCTURE AND SUCCESS
domains
bacterial and archaea
single celled
first organisms on earth
very small
huge population sizes
thrive in diverse environments
cell shapes
cocci (spheres)
bacilli (rods)
spirals
CELL SURFACE STRUCTURES
cell wall
maintains shape
prevents bursting (hypertonic - plasmolysis)
water loss in hypertonic - plasmolysis
bacterial walls
contains peptidoglycan
sugar polymers + polypeptides
archael walls
polysaccharides and proteins
no peptidoglycan
gram staining
classified by wall composiyion
gram positive
thick peptidoglycan
simpler wall
gram negative
thin peptidoglycan
outer membrane
lipopolysaccharides
more antibiotic resistant
capsule and slime layer
sticky outer coating
polysaccharide or protein
functions
adherence
prevent dehydration
protect from immune system
endospores
formed when nurtrients/water low
metabolically inactive
survive extreme conditions
can remain viable for centuries
fimbriae and pili
fimbriae
short
attachment to surfaces
pili (sex pili)
longer
dna exchange
pull cells together
Motility & Internal Organization
Motility
About half show taxis
Movement toward/away from stimulus
Chemotaxis
Response to chemicals
Flagella
Most common motility structure
Scattered or at ends
Different from eukaryotic flagella
Evolution
Motor, hook, filament
Derived from pilus-like proteins
Example of exaptation
Internal Organization
No membrane-bound organelles
Some have membrane infoldings
Metabolic functions
DNA Organization
One circular chromosome
Located in nucleoid
No nucleus
Plasmids
Small DNA rings
Small DNA rings
Reproduction & Genetic Diversity
Binary Fission
Rapid reproduction
Divide every 1–3 hours
Short generation time
Sources of Genetic Diversity
Rapid reproduction
Mutation
Genetic recombination
Genetic Recombination
DNA from two sources
Horizontal gene transfer
Transformation
Transformation
Can gain pathogenic traits
Transduction
Transduction
Accidental during phage cycle
Conjugation
DNA transfer cell-to-cell
Requires pilus
F Factor
Fertility factor
Can be plasmid or chromosomal
F⁺ Cells
Donors
F⁻ Cells
Recipients
Hfr Cells
F factor in chromosome
High recombination frequency
R Plasmids
Carry antibiotic resistance genes
Often multiple resistances
Spread rapidly via conjugation
Metabolism & Nutrition
Energy Source
Chemotrophs → chemicals
Phototrophs → light
carbon source
Autotrophs → CO₂
Heterotrophs → organic compounds
Nutrition Modes
Photoautotroph
Chemoautotroph
Photoheterotroph
chemoheterotroph
oxygen use
obligated aerobes
obligated anaerobes
facultative anaerobes
Nitrogen Metabolism
Nitrogen fixation
N₂ → NH₃
Essential for amino acids & nucleic acids
Metabolic Cooperation
Example: Anabaena
Heterocysts fix nitrogen
Photosynthetic cells share carbohydrates
Biofilms
Surface-coating colonies
Cell signaling
Nutrient channels
Problems
Medical device contamination
Tooth decay
Antibiotic-resistant infections
Prokaryotic Diversity
Bacteria
Most familiar prokaryotes
Most familiar prokaryotes
Groups
Proteobacteria
Chlamydias
Spirochetes
Cyanobacteria
Gram-positive bacteria
Archaea
Unique traits
Extremophiles
Types
Extreme halophiles
Extreme halophiles
Methanogens
Groups
Euryarchaeota
TACK supergroup
Lokiarchaeotes (close to eukaryotes)
Prokaryotes & the Biosphere
Chemical Recycling
Decomposers
Carbon cycling
Nitrogen fixation
Soil nutrient availability
Symbiosis
Mutualism
Commensalism
Parasitism
Pathogens cause disease
Prokaryotes & Humans
Mutualistic Bacteria
Gut microbiome
Gut microbiome
Gut microbiome
Pathogenic Bacteria
Cause many diseases
Example: tuberculosis