Prokayotic vs Eukaryotic Cells

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Prokayotic vs Eukaryotic Cells

• Functional Anatomy

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Typical Bacterial Cell
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Typical Eukaryotic Cells
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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 membrane-bound organelles
• DNA associated with histones
• cell walls never contain peptidoglycan
• 80s ribosomes
• Smallest about size of largest prokaryote

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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

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Common Bacterial Shapes

• Cocci - spherical

• Bacilli rods
• Spirillum - spiral

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Other, Less Common Shapes

• Vibrio comma
• Coccobacillus -
• Square
• Star

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Common Cell arrangements

• Cocci

• Bacilli

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Prokaryotic Anatomy from the Outside In

• Glycocalyx
• Appendages
• Cell Wall
• Bacterial Cell Membranes
• Inside the Cell

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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

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Appendages

• Flagella
• Tail-like structures extending out from
  glycocalyx
• Functions in movement of the bacterial cell
• Complex structure

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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

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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

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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

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Gram Cell Wall
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Gram Cell Wall
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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

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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