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Cells M.Prasad Naidu MSc Medical Biochemistry, Ph.D.Research Scholar
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 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.
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 • 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)
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 http://www.ucmp.berkeley.edu/alllife/virus.html
Viruses • Contains nucleic acid 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
