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.

• They are both membrane bound.

• They both have ribosomes .

• They have similar basic 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 CO2 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