Virus

Cells

Organized labor at its finest!

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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

• 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



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Virus