PROKARYOTES

THEY ARE EVERYWHERE

The Major Similarities Between the Two Types of Cells (Prokaryote and eukaryote) Are: They both have DNA as their genetic material.DNA They are both membrane bound.membrane They both have ribosomes.ribosomes They have similar basic metabolism.metabolism They are both amazingly diverse in forms.

How Prokaryotes Differ from Eukaryotes Smaller and lack membrane bound organelles Have cell walls but composition is different from that of plants and fungi Have simplier genomes –Differ in genetic replication –Protein synthesis –recombination

Prokayotes Have a Tremendous Impact on the Earth Small percentage cause diseases Decomposers –Key to life-sustaining chemical cycles Form symbiotic relationships –Mitochondria and Chlorophast may have evolved from such symbiosis

Three Domains

Two Kingdoms of Prokaryotes Archaebacteria –Evolved from the earliest cells –Inhabit extreme environments Eubacteria –Modern prokaryotes –More numerous

Structure Cocci (spheres) Bacilli (rods) Spirilla and spirochetes (helices)

Prokaryotic Cell Wall Major material is PEPTIDOGLYCAN –Modified sugar polymers cross-linked by short polypeptides –Exact composition varies among species –Some antibiotics work by preventing the formation of cross links thus preventing the formation of a functional cell wall

Gram Stain – a Stain Used to Distinguish Two Groups of Bacteria Gram-PositiveGram-Positive –Have simple walls with large amounts of peptidoglycan –Stain blue Gram-NegativeGram-Negative –More complex with less –More complex with less amounts of peptidoglycan –Outer lipopolysaccharide- containing membrane –Stain pink –Often pathogenic

50% of Bacteria Use One of Three Mechanism to Move 1.Flagella 2.Filaments 3.Gliding Taxis – movement to or away from a stimulus. Stimuli may be: –Phototaxis –Chemotaxis –magnetotaxis

Cellular and Genomic Organization Infolding of the plasma membrane – cellular respiration in aerobic bacteria Cyanobacteria have thylakoid membranes Genome as 1/1000 as much DNA as that of a eukaryote One double stranded, circular DNA DNA concentrated in the nucleoid region Contain plasmids Ribosomes are smaller and have different proteins and RNA content from eukaryotes –This allows some antibiotics to block bacterial protein production will not adversely affecting the eukaryote proteins

Binary fission Transformation Conjugation Transduction Endospores Prokaryotes Grow and Adapt Rapidly

Prokaryotes May Be Grouped According to How They Obtain Energy Photoautotrophs – photosynthetic and use light for energy Chemoautotrophs – need only CO 2 as a source of carbon and obtain energy by oxidizing inorganic substances Photohetrotrophs – use light to make ATP but must obtain carbon in organic form Chemoheterotrophs- must consume organic material for both energy and carbon