Chapter4

Chapter 4: Cellular Structure and Functions

Cell Shape and Size
- 4.1 Cell Morphology
- 4.2 Significance of Smallness
Cytoplasmic Membrane and Transport
- 4.3 Cytoplasmic Membrane in Bacteria and Archaea
- 4.4 Functions of Cytoplasmic Membrane
- 4.5 Membrane Transport
Cell Walls of Prokaryotes
- 4.6 Peptidoglycan
- 4.7 Outer Membrane: Gram (-) Bacteria
- 4.8 Cell Walls of Archaea
Other Cell Surface Structures and Inclusions
- 4.9 Cell Surface Layers, Pili, and Fimbriae
- 4.10 Cell Inclusions
- 4.11 Gas Vesicles
- 4.12 Endospores
Microbial Locomotion
- 4.13 Flagella and Motility
- 4.14 Gliding Motility

Cocci
- Spherical or oval
- Sarcina: 3D cubes
- Strepto-: in chains
- Staphylo-: grape-like clusters
Other Shapes
- Rod/Bacilli
- Spirillum
- Spirochete
- Club-shaped
- Filamentous

Size Range
- 0.2 µm to > 700 µm in diameter
- Most cultured rod-shaped bacteria: 0.5 – 4.0 µm in diameter, < 15 µm in length
- Eukaryotic cells: 10 to > 200 µm in diameter
Significance of Size
- Smaller cells have a higher surface-to-volume ratio, leading to:
  - Faster nutrient uptake
  - Faster growth
  - Higher mutation chance for adaptation
- Lower size limit: 0.15 µm diameter is the theoretical borderline.

Composition
- Membrane lipids (phospholipids and hopanoids)
- Membrane proteins (transmembrane, integral, peripheral)
Functions
- Permeability barrier
- Anchor for membrane proteins
- Energy conservation (proton motive force)

Types of Transport
- Simple transport (H+ driven)
- Group translocation (requires 3 components)
- ABC transporter (requires 3 components)
Transport Events
- Uniport, Antiport, Symport

Peptidoglycan Structure
- Rigid structural layer with a 3D net-like structure
- Thick in Gram-positive (G+) and thin in Gram-negative (G-) bacteria
Composition
- Alternating N-acetylglucosamine (G) and N-acetylmuramic acid (M)
- Crosslinkage differences