The Cell Theory

Prokaryotes vs. Eukaryotes

I. Structure, function, and reproduction of prokaryotesA. Most prokaryotes are unicellular. 1.Some species form aggregates of two or more individuals.B. Three (3) common shapes: cocci (round); bacilli (rod); helical (spiral)

The world of prokaryotes

C. Theyre everywhere! Collective prokaryote biomass outweighs all eukaryotes combined by at least tenfold. They exist almost everywhere, including places where eukaryotes cannot.

Most prokaryotes are beneficial; we couldnt live without them. (e.g. Nitrogen-fixing bacteria)

Lyme disease: Caused by a spirocheteSome cause illness bubonic plague, diphtheria, salmonellaApproximately 5000 species have been identified. Estimates of prokaryote diversity range from 400,000 to 4,000,000 species.

D. Bacteria and Achaea are the two main branches of prokaryote evolution

Achaea are thought to be more closely related to eukaryotes than to bacteria.E. Most prokaryotes secrete sticky substances that form a protective layer and enable them to adhere to substrates.1. The sticky protective layer secreted by prokaryotes is called the capsule.2. Some prokaryotes adhere to substrates using Pili. (Pili are thin, protein tubes originating from the cytoplasmic membrane) a. Some Pili are specialized for DNA transfer. This process is called conjugation; note for later in class.

F. Almost all prokaryotes have cell walls external to the plasma membrane.1. Cell walls maintain cell shape.2. Cell walls are composed of peptidoglycan.(a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria, forming the cell wall)

G. Cellular and genomic organization of prokaryotes is different from that of eukaryotes 1.Prokaryotes have no nucleus.2. The nucleoid region in a prokaryotic cell consists of a concentrated mass of DNA. This mass of DNA is usually one thousand times less than what is found in a eukaryote.

Specialized membranes of prokaryotes

NnucleoidProkaryotic cells

DiagramComponentsof a prokaryoteCytoplasmRibosomesNuclear ZoneDNAPlasmidCell MembraneMesosomeCell WallCapsule (or slime layer)Flagellum

PeptidoglycanPeptidoglycanGram PositiveGram NegativePlasma membranePlasma membraneOuter membraneLipopolysaccharide layer

PROCARYOTES

Photosynthesis evolved early in prokaryotic life Cyanobacteria started to produce O2 about 2.7 billion years agoContrasting hypotheses for the taxonomic distribution of photosynthesis among prokaryotes.

Heliobacteria: Causes stomach ulcers

2. Chlamydias- Parasitic; survive only within cells of animals- Some cause STDs e.g. Chlamydia

3. Spirochetes- Helical heterotrophs- Some cause STDs e.g. syphilis

Mycoplasma shown covering a human cell; some species of mycoplasmas cause walking pneumonia

5. Cyanobacteria- Oxygenic photosynthesis, and chloroplasts evolved from them.Ecological impacts of prokaryotes A. Prokaryotes are links in the recycling of chemical elements B. Many prokaryotes are symbiotic (2 organisms living in direct contact with each other). Mutualism both symbiotic organisms benefit- e.g. Nitrogen-fixing bacteria like Rhizobium: plant obtain organic nitrogen, Rhizobium gets energy in the form of sugars that the plant produces.

Are all prokaryotes disease producing germs?Without prokaryotes ecosystems would collapse!

53.10Humans use prokaryotes in research and technology Examples:

Sewage treatmentBioremediationChemical & Medical productionResearch (genetic engineering, etc.)

Eukaryotic and Prokaryotic CellsProkaryote = without a nucleus Eukaryote = with a nucleus

EUKARYOTE DiagramComponents of a EukaryoteCytoplasmNucleus with NucleolusMitochondriaChloroplastRibosomesRough Endoplasmic ReticulumSmooth Endoplasmic ReticulumGolgi bodyVacuolesComponents of a Eukaryote continuedLysosomesCytoskeletonCentrioleCilium and FlagellumMicrovillusCell membraneCell WallComparing Prokaryotic and Eukaryotic CellsProkaryotesEukaryotesHave cell wall or membraneHave DNAHave cytoplasmHave Organelles

Have a nucleus

Have membranes surrounding organelles

Are mostly bacteriaInclude all plant and animal cells

33Summary of the differences!Prokaryotic CellsEukaryotic cellssmall cells (< 5 mm)larger cells (> 10 mm)always unicellularoften multicellularno nucleus or any membrane-bound organellesalways have nucleus and other membrane-bound organellesDNA is circular, without proteinsDNA is linear and associated with proteins to form chromatinRibosomes are small (70S)Ribosomes are large (80S)no cytoskeletonalways has a cytoskeletoncell division is by binary fissioncell division is by mitosis or meiosisreproduction is always asexualreproduction is asexual or sexual