Virus

Cells

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What is the importance?
• Division of labor
• Increased Surface Area
• Regulation


Prokaryotes
• Simplest
• No organelles
• No nucleus
• No membrane bound organelles
• DNA uncomplexed by histones


Prokaryotes


Prokaryotes
• Prokaryotes can live in the coldest, hottest,
most acidic and most highly pressurized
environments.
• They can live in places such as beneath the
earth in bare rock, under glaciers, floating
around in clouds and miles down on the sea
floor at temperatures greater than 100 C.


Types of Prokaryotes
• Archaea
• Bacteria


Archaea
• Most Archaea are anaerobic (living in the absence of
Oxygen)
• Many live in uncommon and extreme environments, i.e.
hot springs, Arctic ice floes, highly saline waters and
highly acidic or alkaline soils.
• Nearly half of the known Archaea are Methanogenic,
meaning that they give off methane as a by-product of their
metabolic activity.
• The Archaea have a diverse variety of shapes and exist not
only as rods and dots (cocci) like bacteria but also as
triangles, discs, plates and cup-shapes.


Bacteria


Bacteria
• Bacteria live mostly on the surfaces of
objects where they grow as colonies.
• Bacteria are important in making soil,
feeding cows, controlling insects, making
medicines, making bioplastics, making
plants grow, degrading pollutants such as
oil and plastics as well as in causing
disease.

Bacteria
• Most bacterial species are un-named and
unidentified
• Tens of thousands of species have been
isolated
• There are more than 15,000 known species
of bacteria living in the sea
• Most famous is E.coli (Escherichia coli)


E. coli


E.coli
– well studied
– cell envelope
– plasma membrane constitutes #2
– pili (for adherence to cells)
– flagella (for propulsion through aqueous
environment)
– chemistry similar to ours

E.coli
• Some strains frequently cause diarrhea in
travelers, and it is the most common cause of
urinary tract infections
• One strain, designated O157:H7, is particularly
virulent and has been responsible for several
dangerous outbreaks in people eating
contaminated food (usually undercooked
hamburger).
• Several important drugs (insulin, for example) are
now manufactured in E. coli


Eukaryotes
• More complex
• More DNA
– Has to be folded
– histones (positively charged proteins)


Structure


Plasma membrane
– compartmentalization
– huge number of proteins
– transporters (nutrient carriers)
– receptors (signal transduction)
– lipids and protein
– semi-permeable (polar and charged ions
cannot cross freely)

Nucleus
• double membrane
• contains DNA
– genetic material
– chromatin vs. chromosomes
– nucleolus has RNA
– histones: proteins that are positively charged
that wind up DNA


Endoplasmic Reticulum
• Rough ER:
– ribosomes
– protein synthesis occurs here for those proteins
that will be routed out of cell
• Smooth ER
– lipid synthesis
– metabolism of drugs and toxic substances


Golgi
• Cellular post office
• Proteins synthesized in the ER are packaged
with extras such as
• SO42-, carbohydrates, lipid moieties
• Then, the proteins are directed to either the
cell membrane to outside the cell or within
the cell.
• In other words, the proteins are flagged for
their next destination

Mitochondria
• ATP production
• has its own DNA
• uses nutrients to make energy
• In plants, chloroplasts makes sugar from
sunlight
• Endosymbiotic theory


Lysosomes (Animal Cells)
• Recycling centers can breakdown proteins
• in plant cells these are vacuoles


Peroxisomes
• Breakdown H2O2


Cytoskeleton
• internal organization, assists the plasma
membrane in retaining cell shape, and
allows the cell to move
• microtubules
– rods from tubulin
– arrangement
– motion
• Actin: protein filament for cell rigidity
• Myosin: moves along actin using ATP

Viruses


Viruses
• Contains DNA surrounded by protective shell or
capsid
• Uses host cells enzymes and ribosomes for
replication
• Lysogenic phase: viruses may remain dormant
inside host cells for long periods. There is no
obvious change in their host cells
• Can enter the lytic phase: new viruses are
produced, assemble, and burst out of the host cell.
• The cell is killed and other cells are infected

Famous Viruses
• Smallpox, common cold, chickenpox,
influenza, shingles, herpes, polio, rabies
• Ebola
• AIDS


Bacteriophages
• Viruses that infect bacteria
• Commonly used in molecular biology
• DNA isolated from tissue---> Packaged into
bacteriophage DNA---> Bacteria culture
grown and infected with bacteriophage--->
DNA of interest is replicated and studied
either on DNA level or protein level


Virus

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