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Biology Unit 10
Prokaryotes
A. Introduction to the Domains Bacteria and Archaea
1. Unicellular
2. Prokaryotes
a. No nucleus
b. No organelles
c. Single strand of DNA
3. Most numerous group of organisms on the Earth
a. A single gram of soil can contain 5 billion of them!
b. They outnumber all members of the other 4 kingdoms
combined!
c. So small – on average, they are about 1000 times smaller
Prokaryotes
4.
They can live just about anywhere
a. Can exist 3.9 miles high in the atmosphere riding
on dust particles
b. Can live in hot springs that are around 208
degrees F
Prokaryotes
5.
Their need for oxygen:
a. Obligate anaerobes – cannot live in the presence
of oxygen
1. Produce methane gas
2. Live in marshes, bottom of lakes, digestive
tracts of animals
b. Obligate aerobes – need oxygen in their
environment
c. Facultative aerobes – can survive with our
Prokaryotes
6.
Archaea vs Bacteria:
Characteristic s
Archaebacteri a
Eubacteria
Cell Type: Prokaryote Prokaryote
Cell Membrane: Types of Lipids Different Types of Lipids
Prokaryotes
a. Archaebacteria that live in extreme conditions:
1. Thermoacidophiles
a. Live in highly acidic soils and hot springs
where temps reach 230 degrees F
b. Live in hydrothermal vents deep on ocean
floor
2. Methanogens
a. Live in anaerobic environments like sewage,
swamps, intestines
Prokaryotes
3. Halophiles
a. Salt-lovers
b. Live in areas with high salt concentration
like Great Salt lake, Dead Sea
c. Metabolize the salt to produce their ATP b. Eubacteria are all the other remaining types of
Prokaryotes
B.
Bacterial Structure
1.
Three shapes of bacteria: used to classify the
over 16,000 different species
a. Cocci – round shapeProkaryotes
Prokaryotes
3. Their cell wall (found outside the cell membrane):
a. Maintains cell shape
b. Provides physical protection
c. Prevents the cell from bursting in a hypotonic
environment
1. In a hypertonic environment, the cell wilts and they cannot reproduce
a. This is why salt is used to preserve some foods d. Cell walls can contain peptidoglycan:
1. Large molecule of carbohydrates and protein
2. Gives strength and shape to the cell
Prokaryotes
a. Gram+ bacteria (purple stain):
1. Large amounts of peptidoglycans in cell
wall
b. Gram- bacteria (pink stain):
1. Small amounts of peptidoglycans in cell
wall
2. More complex and dangerous
3. Life-threatening bacteria b/c outer
Prokaryotes
4.
Some have a capsule
a. Sticky layer outside the cell wall b. Helps them cling to surfaces
c. Helps cells from drying out during dry periods d. Protects them from the host’s immune system
1. Studies have shown that the thicker the capsule,
Prokaryotes
5. Some have a flagella
a. Long, hair-like projection
b. Allows them to move
c. Acts like a tiny propeller
6. Some form an endospore
a. Under harsh conditions, certain bacteria can form a thick, protective wall around their DNA
b. The rest of the cell may die, but the endospore (with DNA inside) survives
c. Can withstand high temperatures, boiling, drying, and radiation
Prokaryotes
C.
Nutrition
1.
Autotrophs - photosynthesize
a. Two types:
1. Photosynthetic – use sun as their energy
source
a. Example – cyanobacteria (blue-green algae)
2. Chemosynthetic – use chemicals as their
Prokaryotes
2.
Heterotrophs – absorb small food molecules
through their cell membrane
a. Some feed on dead organic matter - saprobes
1. Feed on dead plants and animals 2. Decomposers
3. Break things down
b. Some live in hosts – parasites
Prokaryotes
D.
Reproduction
1.
Under ideal conditions, many bacteria are able
to grow to full size and reproduce every 30
minutes
a. If this persists, in about 15 hours, 1 bacterial cell
will produce 1 billion cells!
Prokaryotes
Prokaryotes
3.
Conjugation
a. Bacteria are able to
exchange genetic material when parts of their
chromosomes travel through a hollow bride of pili formed to connect two or more
cells!
b. In the picture to the right,
plasmid DNA is being
Prokaryotes
E.
Conditions needed for optimal bacterial
growth
1.
Moisture
2.
Temperature – 80 to 100 degrees F is optional
3.pH
Prokaryotes
F.
Some importance of Bacteria
1.
Cause many human diseases
2.Cause food to spoil
3.
Decomposers break down dead organic matter
and recycle nutrients back into environment
4.
Bacteria produce needed vitamins in human
intestines
5.
Many foods are made with bacteria – yogurt,
cheese, wine, vinegar…
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Biology Unit 10
Viruses
A. Virus
1. virology – the study of viruses
2. virus - a tiny infectious particle made of nucleic acid (DNA or RNA) and a protein coat
3. viroid – infectious particles that cause disease in plants and are made of RNA and no protein coat
4. prion – infectious particle made only of protein that cause other proteins to not fold correctly
a. prevents protein from functioning b. example – mad cow disease
Viruses
5. Are they alive or not alive?
a. unable to reproduce on their own – need a host b. but, they do respond to their environment
c. but, they have genes and can reproduce
Viruses
6. structure:
a. much smaller than bacteria b. 2 parts:
1. core of either DNA or RNA
2. capsid – protein covering the DNA or RNA c. can have - tail, tail fibers
capsule
nucleic acid (DNA or RNA)
tail
Viruses
7. each type of virus can infect only certain hosts
a. a virus identifies its host by fitting its surface proteins
to receptor molecules on the surface of the host cell
– like a lock and key
Viruses
B. Replicating of Viruses
1. lytic cycle
a. virulence – the ability of a pathogen to affect cells b. in the lytic cycle:
1. viral attachment to host cell
2. virus releases the contents of it’s capsid – DNA or RNA 3. once inside the cell, replication and transcription
take place
4. new viral parts are made and assembled into new viruses
5. enzymes produced by the virus cause the cell to burst open – lysis
a. this releases the new viruses which can
Viruses
c. when a virulent virus attacks a cell, it can
sometimes
produce hundreds of viruses in as little as 30
minutes, then
Viruses
2.
lysogenic cycle
:
a. not all viruses invade a host cell and immediately destroy it
b. some simply combine their DNA with the host’s DNA, remaining “inactive”
c. each time the DNA replicates, the viral DNA replicates along
with it.
d. will eventually become virulent (active) and switch to the lytic
Viruses
e. example – AIDS
1. a person can be HIV +, meaning the virus is in the lysogenic stage. Once the virus becomes active (lytic
stage) the person has AIDS and all the symptoms that
Viruses
C. Vaccines and Epidemics
1. a substance that stimulates the body’s own immune system
response against a foreign invader
2. are made from the same pathogen but in a weakened version
a. this allows the body to build up antibodies to the pathogen
without them feeling the effects of the disease
3. epidemic – a rapid outbreak of an infection that affects many
