CHAPTER 4: PROKARYOTIC &

EUKARYOTIC CELLSMicrobiologyAugust 12, 2013

COMPARING PROKARYOTES AND EUKARYOTES oThey are chemically similar

oNucleic acidsoProteinsoLipidsoCarbohydrates

oBut there are many differences between the 2 types of cells

DIFFERENCES (PAGE 100, TABLE 4.2)ProkaryotesoDNA is circular and not enclosed

oNo special proteins associated with DNA

oLack membrane-bound organelles and nucleus

oCell walls contain peptidoglycan (sugar)

oCell division by binary fission

Eukaryotes

oDNA is in the cell’s nucleus

oDNA is compacted into chromosomes

oSeveral membrane-bound organelles

oCell walls (if present) are chemically simple

oCell division is by mitosis

PROKARYOTESoArchaea and BacteriaoMostly identified by shape, chemical make-up, nutritional requirementsoThree different shapesoCoccusoBacillusoSpiral

SHAPES OF BACTERIAL CELLS

COCCI SHAPE

Streptococcus pyogenes

BACILLI SHAPE

Bacillus cereus

EXTERNAL STRUCTURES TO CELL WALL (PG 80)oGlycocalyx = a sugar coat that surrounds cells for protectionoCapsule or slime layer

oFlagella = a long filamentous appendage used for locomotion

oPilus = used to join cells together to transfer bacterial DNA through conjugation

TYPES OF FLAGELLA

CELL WALL

oProvides shape of cell

oAlmost all prokaryotes have cell wallsoArchaea may lack cell walls or lack cell walls composed of peptioglycan

oComposed of a complex sugar called peptidoglycan

oMain function = “prevent bacterial cells from rupturing when the water pressure inside the cell is greater than that outside the cell” (page 85)

CELL WALLS OF PROKARYOTESGram Positive (+)

±Many layers of peptidoglycan

±Stains purple because dye is trapped

±Cell well is (+) charged

Gram Negative (-)

±Thin layer of peptidoglycan

±Stains pink because stain is released

±Cell well is (-) charged

INTERNAL STRUCTURES OF CELL WALLSoPlasma membrane = think structure lying inside the cell walloPhospholipid bilayer

oCytoplasm = substance inside the lipid bilayer that is composed for 80% water, gelatinous

oNucleoid = the nuclear area of the bacterial cell which contains a single continuous, circular, double strand of DNA

oRibosomes = the site of protein synthesis

oEndospores = a specialized resting cell that is highly durable in extreme environmentsoFormed inside the cell membrane

MOVEMENT ACROSS MEMBRANESoSimple diffusion = the net movement of ions from high concentration to low concentration

oFacilitated diffusion = the movement of ions from high to low concentration by the action of transporters

oOsmosis = the net movement of solvent molecules across a selectively permeable membrane from an area of high to low concentrationoIsotonic solutionoHypotonic solutionoHypertonic solution

oActive transport = the cell must use ATP to move substances across the plasma membrane

ohttp://youtu.be/yz7EHJFDEJs

PART 2: EUKARYOTES Continuation of Chapter 4 notes

EUKARYOTES

oEukaryotes include:oAlgaeoProtozoaoFungioPlantsoAnimals

EXTERNAL STRUCTURESoFlagella = external structures used for locomotion and are long filaments, few in numberoCilia = external structures used for locomotion and are numerous and short projections

http://youtu.be/sZlDAAu2oZ0

CELL WALL

oNot all eukaryotes have cell walls, some have a pellicle or plasma membraneoOther cell walls are made of chitin or celluloseoNO PEPTIDOGLYCAN

INTERNAL STRUCTURES

oCytoplasm = the substance inside the cell membrane and outside the nucleusoCytoskeleton = structures that provide support for the eukaryotic cell. It include microfilaments, microtubules, and intermediate filaments.oRibosomes = the site of protein synthesis

oOrganelles are structures with specific shapes and specialized functions

oNucleusoEndoplasmic ReticulumoGolgi ComplexoLysosomesoVacuolesoMitochondria “the powerhouse of the cell”oChloroplastsoCentrosome

EVOLUTION OF THE EUKARYOTIC CELL

oEndosymbiosis theory was proposed by Lynn MargulisoStates that larger bacterial cells lost their cell walls and engulfed smaller bacterial cellso“Eukaryotes come from prokaryotes”oSymbiosis means “living together”