Transcript Prokayotic and Eukaryotic Cells

Prokayotic vs Eukaryotic Cells
Functional Anatomy
Typical Bacterial Cell
Typical Eukaryotic Cells
Prokaryote vs Eukaryote
Overview

Prokaryote or “before
nucleus”
– no membrane-bound
nucleus
– no other membrane-bound
organelles
– DNA not associated with
histones
– cell walls almost always
contain peptidoglycan
– 70s ribosomes
– Largest about size of
smallest eukaryote

Eukaryote or “true
nucleus”
– membrane bound nucleus
– many other membranebound organelles
– DNA associated with
histones
– cell walls never contain
peptidoglycan
– 80s ribosomes
– Smallest about size of
largest prokaryote
Prokaryotic Cells
 Size
– Smallest of living cells
» 0.2 to 2.0 μm in diameter
» 2 to 8 μm in length
– Most eukaryotes bigger
– Viruses much smaller
Common Bacterial Shapes
 Cocci
- spherical
 Bacilli
– rods
 Spirillum
- spiral
Other, Less Common Shapes
 Vibrio
– comma
 Coccobacillus
 Square
 Star
-
Common Cell arrangements
 Cocci
 Bacilli
Prokaryotic Anatomy from the
Outside In
 Glycocalyx
 Appendages
 Cell
Wall
 Bacterial Cell Membranes
 Inside the Cell
Glycocalyx

Sticky substances that surround cells
– Firmly attached = capsule
– Loosely attached = slime layer

Composition varies with species
– Polysaccharides
– Polypeptides
– Both

Function
– Protect cell from phagocytosis and dehydration
– Aid in attachment to various surfaces
– May inhibit movement of nutrients from cell
Appendages
 Flagella
– Tail-like structures extending out from
glycocalyx
– Functions in movement of the bacterial cell
– Complex structure
Structure of Flagella
 Filament
– Long tail-like region
– Constant diameter
– Made of protein
 Hook
– Filament attachment
 Basal
body
– Small central rod
inserted into a series
of rings
Cell Wall
 Rigid
 Composed
mostly of peptidoglycan
– Found only in bacterial cell walls
– Amount differs in gram+ and gram- cells
 Protects
cell in environments with
osmotic pressures
Peptidoglycan
 Glycan
portion
– NAG
» N-acetylglucosamine
– NAM
» N-acetylmuramic acid
– Linked in rows of
10-65 sugars
 Peptide
portion
– Adjacent rows are
linked by
polypeptides
Gram+ Cell Wall
Gram – Cell Wall
Atypical Cell Walls
 Mycoplasmas
– Lack cell wall
– Smallest known bacteria
 Archeobacteria
– Cell walls contain pseudomurein rather than
peptidoglycan
– Lacks D-amino acids found in bacteria
 L-forms
– Tiny mutant bacteria with defective cell walls
– Just enough material to prevent lysis in dilute
environments
Inside the Cell Wall


Cell Membrane
Cytoplasm
– 4/5 water and 1/5 dissolved substances
– Most chemical reactions occur here

Ribosomes
– Abundant in cytoplasm
– 70s

Nuclear region
– Central 10% of cell volume
– DNA in single circular chromosome

Inclusions
– small bodies within cytoplasm
– Many different types