Download PROKARYOTES

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-Positive
– Have simple walls
with large amounts
of peptidoglycan
– Stain blue
• Gram-Negative
– 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
Prokaryotes Grow and Adapt Rapidly
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Binary fission
Transformation
Conjugation
Transduction
Endospores
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