8/8/2019 Prokaryotic Cells Final

1/22

8/8/2019 Prokaryotic Cells Final

2/22

General Information

The prokaryotes are a groupoforganisms that lackacellnucleus (=karyon),oranyothermembrane-boundorganelles

Few prokaryotessuch asmyxobacteria havemulticellularstagesintheir

life cycles Prokaryotesare the earliestandmostprimitive formsoflife on earth

8/8/2019 Prokaryotic Cells Final

3/22

General Information

Asorganizedinthe Three Domain

System,prokaryotesinclude bacteria

andarchaeans.

Able to live andthrive invarioustypesof

environmentsincluding extreme habitats

such as hydrothermal vents, hot

springs,swamps, wetlands,andthe

gutsofanimals

The prokaryotesare dividedintotwo

domains:the bacteria andthe archaea

8/8/2019 Prokaryotic Cells Final

4/22

Archaea

Theyare a groupofsingle-celledmicroorganisms

A single individual orspeciesfromthisdomainiscalledanarchaeon

They have nocell nucleusoranyotherorganelles

Archaea have anindependentevolutionary

history andshow manydifferencesintheirbiochemistry

8/8/2019 Prokaryotic Cells Final

5/22

Eubacteria

The bacteria are a large groupofunicellular,prokaryote,microorganisms.

Wide range ofshapes,rangingfromspheres torodsandspirals

Bacteriaare ubiquitous

There are approximatelytentimesasmanybacterial cellsinthe humanflora ofbacteriaasthere are humancellsinthebody

8/8/2019 Prokaryotic Cells Final

6/22

Eubacteria

Large numbersofbacteriaonthe skin andasgutflora

The vastmajorityofthebacteriainthe bodyare

rendered harmlessbytheprotective effectsoftheimmune system(parasites),andafew are

beneficial

8/8/2019 Prokaryotic Cells Final

7/22

Types ofEubacteria

Heterotrophs -theyfeedonorganiccompounds,producedbyotherorganisms

Saprophytes- obtainnutrientsfromdeadorganismsorbreakdownorganicmatter

Heterophic aerobes :oxygenrequiring / Heterophic-anaerobes:can live withoutoxygen

8/8/2019 Prokaryotic Cells Final

8/22

Prokaryotic Cell Structure

Prokaryoticcellsare notascomplexas

eukaryoticcells

Have notrue nucleusasthe DNA isnot

contained withinamembrane or

separatedfromthe restofthe cell

DNA iscoiledupinaregionofthe

cytoplasmcalledthe nucleoid

8/8/2019 Prokaryotic Cells Final

9/22

Prokaryotic Cell Structure

Capsule - Foundinsome

bacterial cells,thisadditional

outercovering protectsthe cell

Cell Wall - Outercovering ofmostcells

Cytoplasm - A gel-like

substance composedmainlyof

waterthatalsocontainsenzymes,salts,cell

components,andvarious

organicmolecules.

8/8/2019 Prokaryotic Cells Final

10/22

Prokaryotic Cell Structure

Cell Membrane or Plasma Membrane - Surroundsthecell'scytoplasmandregulatesthe flow ofsubstancesinandoutofthe cell.

Pili - Hair-like structuresonthe surface ofthe cell thatattach tootherbacterial cells..

Flagella - Long, whip-like protrusionthataidsincellularlocomotion.

8/8/2019 Prokaryotic Cells Final

11/22

Prokaryotic Cell Structure

Ribosomes - Cell structuresresponsible forproteinproduction.

Plasmids - Gene carrying,circularDNA structuresthatare notinvolvedinreproduction.

Nucleiod Region - Areaofthe cytoplasmthat

containsthe single bacterial DNA molecule.

Endospores it hasprotective function

8/8/2019 Prokaryotic Cells Final

12/22

8/8/2019 Prokaryotic Cells Final

13/22

Binary Fission

Mostprokaryotesreproduce asexually through aprocesscalledbinaryfission

DNA molecule replicating andboth copiesattaching tothe cell membrane.

Cell membrane beginsto grow betweenthe two DNAmolecules.

A cell wall thenformsbetweenthe two DNA moleculesdividing the original cell intotwoidentical daughtercells.

8/8/2019 Prokaryotic Cells Final

14/22

8/8/2019 Prokaryotic Cells Final

15/22

8/8/2019 Prokaryotic Cells Final

16/22

Cyanobacteria

Cyanobacteriaisaphylumofbacteria

thatobtaintheirenergythrough

photosynthesis.

Itisalsoknownasblue-greenalgae,

blue-greenbacteriaorcyanophyta. Thename "cyanobacteria" comesfromthe

colorofthe bacteria(Greek:

(kyans)=blue).

Theyare asignificantcomponentofthe

marine nitrogencycle. Theyare a

significantcomponentofthe marine

nitrogencycle; Theyare alsofoundin

habitatsotherthanthe marine

environment

8/8/2019 Prokaryotic Cells Final

17/22

Cyanobacteria

y Veryclose instructure andfunctiontothe true bacteria.They have all the structurestypical forbacteria, exceptthe flagella.

y Have a lotofmembrane lamellae (thylakoids)situatedinthe cytoplasm.

y Contain greenpigmentchlorophyll which helpthemtoabsorb energy,photosynthesize andobtainorganicsubstances. Thisis whycyanobacteriaare calledautotrophs.

8/8/2019 Prokaryotic Cells Final

18/22

Cyanobacteria

Classification:

The cyanobacteria were traditionally

classifiedbymorphologyintofive sections.

Firstthree are Chroococcales,

Pleurocapsales,Oscillatoriales.

Lattertwoare NostocalesandStigonematales

8/8/2019 Prokaryotic Cells Final

19/22

8/8/2019 Prokaryotic Cells Final

20/22

Importance ofbacteria

Bacteriaplayanimportantrole innature. Theyare amajorfactorinthe processofdecay.

Some bacteriaare nitrogen-fixing theycapture nitrogenfromthe

airandinclude itinthe synthesisofproteins.

Bacteriainhabitthe digestive systemsofboth humansandanimals.Inmanycasestheyaidthe breakdownofcellulose,containedinfood.

Cyanobacteriaare most widelyspreadinsoil andinpolluted waterbasins. Theirpresence isanindicatorofthe level ofwaterpolution.

8/8/2019 Prokaryotic Cells Final

21/22

Health Risk

Certaincyanobacteriaproduce cyanotoxins which are toxinsthat

canbe dangerousto humansandanimals.

Several casesofhumanpoisoning have beendocumented.

Recentstudiessaysthatsignificant exposure to high levelsof

cyanobacteriacauses ALS (Lou Gerhig's Disease)

Cyanobacteriacause variousinfectiousillnessesin humansand

animals like dysentery,tetanus,plague, lung inflammation,

tuberculosis, etc.

8/8/2019 Prokaryotic Cells Final

22/22