This is a comprehensive and detailed outline note on theme 3; functional anatomy of a prokaryotic and eukaryotic cell for MBY 161.
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Theme 3: Functional anatomy of a Prokaryotic and Eukaryotic cell
Prokaryote Eukaryote
• One circular chromosome, not in a membrane Paired chromosomes,
in nuclear membrane
• No histones (other prot) Histones
• No organelles Organelles
• Bacteria: peptidoglycan cell walls Polysaccharide cell walls
• Archaea: pseudomurein cell walls
• Binary fission Mitoses- mitotic spindle
Prokaryotic cells
Basic Shapes
• Bacillus (rod-shaped)
• Coccus (spherical)
• Spiral
– Spirillum
– Vibrio
– Spirochete
Flagella
• Outside cell wall
• Made of chains of flagellin
• Attached to a protein hook
• Anchored to the wall and membrane by the
basal body
Fimbriae and Pili
• Fimbriae
– allow attachment
– Hair like appendages – shorter and thinner than flagella
• Pili
– Facilitate transfer of DNA from one cell to another (conjugation)
– Gliding motility
– Twitching motility
– Longer than fimbriae and only one or two/cell
The Cell Wall
• Prevents osmotic lysis
• Made of peptidoglycan (in bacteria)
• Differentiate groups of bacteria (Gram positive or Gram negative)
• Functions
- Maintain shape
- Anchor for flagella
- Can play a role in the ability to cause disease
Peptidoglycan
• Polymer of disaccharide:
– N-acetylglucosamine (NAG)
– N-acetylmuramic acid (NAM)
Gram-Positive Cell Wall
• Thick peptidoglycan
• Teichoic acids
– Lipoteichoic acid links to plasma membrane
– Wall teichoic acid links to peptidoglycan
, • May regulate movement of cations
• Polysaccharides provide antigenic variation (Diagnostic application)
Gram negative Cell Waal
• Thin peptidoglycan
• Outermembrane
• Periplasmic space
Gram-Negative Outer Membrane
• Outer membrane consist of lipopolysaccharides, lipoproteins, phospholipids
• Peptidoclycan is in the periplasm between the outer membrane and the plasma membrane
• Gel like fluid
• Protection from phagocytes, complement, and antibiotics
• O polysaccharide antigen, e.g., E. coli O157:H7
• Lipid A is an endotoxin
• Porins (proteins) form channels through membrane – molecules can pass
Gram-Positive Cell Wall
• 2-ring basal body
• Disrupted by lysozyme
• Penicillin sensitive
Gram –Negative Cell Wall
• 4-ring basal body
• Endotoxin (Lipid a)
• Tertracycline sensitive
Table 1 p 110 (MAI New)
Atypical Cell Walls
• Acid-fast cell walls
– Like gram-positive cell walls (Thin layer of peptidoglycan)
– Waxy lipid (mycolic acid) bound to peptidoglycan
• Mycobacterium
• Mycoplasmas
– Lack cell walls
– Sterols in plasma membrane (protect from lysis)
• Archaea
– Wall-less, or no peptidoglycan
– Walls of pseudomurein (lack NAM and D-amino acids)
– Cannot Gram stain (Appear Gram negative)
Damage to the Cell Wall
• Lysozyme digests disaccharide in peptidoglycan
• Penicillin inhibits peptide bridges in peptidoglycan
• Protoplast is a wall-less cell
• Spheroplast is a wall-less gram-positive cell
– Protoplasts and spheroplasts are susceptible to osmotic lysis
• L forms are wall-less cells that swell into irregular shapes
The Plasma Membrane
• Phospholipid bilayer
• Peripheral proteins
• Integral proteins
• Transmembrane proteins
Fluid Mosaic Model
• Membrane is as viscous as olive oil
• Proteins move to function
• Phospholipids rotate and move laterally
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