Chapter 4 Prokaryote Eukaryote One circular chromosome, not enclosed in a membrane No histones No membrane-bound organelles Paired chromosomes, enclosed in a nuclear membrane Histones Membrane-bound organelles

Prokaryote Eukaryote Peptidoglycan cell walls Binary fission Polysaccharide cell walls Mitosis

Bacterial Shapes and Arrangements Bacilli – rod shaped Cocci – spherical shaped Spiral – have one or more twists Coccobacilli – intermediate between coccus and bacillus Strepto- chain of cells (bacilli or cocci) Staphylo- cluster of cells (cocci)

Some Representative Cocci

Some Representative Bacilli

Prokaryotic Cell Structures

Glycocalyx Outside cell wall Composed of polysaccharide, protein, or both Called or slime layer Allows cell to attach to things may prevent phagocytosis

Capsule Streptococcus pneumoniae and bacillus anthracis are among many bacterial types that may possess capsules.

Flagella Outside cell wall Anchored to the cell wall and membrane Used for motility (i.e. chemotaxis) Promotes spreading of microbe in the disease process

Flagella Arrangement

Axial Filaments In Anchored at one end of a cell and spiral around the cell Rotation causes cell to move

Fimbriae and Pili Hair-like structures Fimbriae allow attachment Pili are used to transfer DNA from one cell to another

Cell Wall Prevents osmotic lysis Made of (in bacteria)

Peptidoglycan Polymer of disaccharide Linked by short polypeptides

Cell Wall Types layer of peptidoglycan layer of peptidoglycan Gram-positive cell walls layer of peptidoglycan Acid-fast cell walls contains Gram-negative cell walls layer of peptidoglycan Contains an outer membrane

Gram-Negative Outer Membrane Provides some protection from host immune system attack, and some antibiotics. Contains Lipid A, an endotoxin derived from lipopolysaccharide (LPS)

Gram Staining of Bacterial Cells Purpose: to distinguish Gram positive from Gram negative bacteria Dyes/solutions used: 1. Crystal violet 2. Iodine (mordant) 3. Alcohol 4. Safranin (counter stain) Gram-positive bacteria: Alcohol does not remove CV/I = purple cells Gram-negative bacteria: Alcohol removes CV/I = pink cells

Plasma Membrane Functions : allows passage of some molecules in and out of cell Site of photosynthesis Site of ATP production Components Membrane proteins Integral peripheral

Plasma Membrane

Fluid Mosaic Model Membrane is as viscous as olive oil. Proteins move freely within phospholipids. Enables their functioning. Phospholipids also move. Enables protein movement and promotes repair.

Movement Across Membranes : Movement of a solute from an area of high concentration to an area of low concentration. : Solute combines with a transporter protein in the membrane. of substances requires a transporter protein and ATP.

Facilitated Diffusion

Movement Across Membranes Osmosis Movement of “water” across a selectively permeable membrane from an area of high water concentration to an area of lower water concentration.

With regard to solutes, cells live under certain environmental conditions. These are: Hypertonic environment Hypotonic environment Isotonic environment

Prokaryotic Cell Structures Cytoplasm is the substance inside the plasma membrane Nucleoid (nuclear area): region of DNA Ribosomes: organelles where proteins are made Inclusions: granules that serve as storage sites for nutrients, enzymes and other substances.

Endospores “Resting” cells Highly resistant to desiccation, heat, freezing, chemicals Many Bacillus and Clostridium species form endospores Bacillus anthracis – anthrax Bacillus botulinum - botulism Clostridium tetani - tetanus

Endospore Formation