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 membrane-

bound 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