Plasma Membrane and Cell Wall

Taxis

- Any movement of bacteria toward or away from a particular stimulus

Gram-positive bacteria

- Bacteria that have a thick peptido glycan cell wall, and no outer membrane. They stain very darkly (purple) in Gram stain.

Gram-negative bacteria

- Bacteria that have complex cell walls with less peptidoglycan but with lipopolysaccharides. Very toxic and hard to treat.

Cell membrane

- Composed of phospholipids and proteins - Phospholipids are polar molecules with a polar (hydrophilic) head and a non polar (hydrophobic) tail

Cell wall of algae

- Contains cellulose and a variety of glycoproteins

Cell wall of archea

- Does not contain peptidoglycan

Intergral proteins

- Extend from one side through the membrane to the other side

Pili (fimbriae)

- Form of bacterial surface projection - More rigid than flagella - Composed of piling proteins - Have adhesive properties - Play an important role as factors in the colonization of epithelial surfaces - Dependent on specific interactions between the adhesions and molecules in the host cell membranes

Glycocalyx

- Formed outside the plasma membrane - Composed of polymeric material - Produced by some bacteria, epithelia, and other cells - Network of polysaccharides - (Bacteria) Coating of macromolecules that protects the cell and sometimes helps the bacterium to adhere to its environments

Cholesterol and hopanoids (plant cell)

- Immobilize the first few hydrocarbon groups of the phospholipid molecules - Makes the lipid biller less elastic and decreases permeability to small water-soluble molecules

Cell wall of plant cell

- Made of polysaccharides - Cellulose, hemicellulose, and pectin

Cell wall

- Maintain the shape of a cell and to protect the cell from any physical and chemical damage - (Bacteria) Protects them from hostile environments, including protection from the immune system of a host

Biofilm

- Microbial community enclosed by an extracellular polysaccharide polymeric matrix - Mineral crystals, corrosive particles, blood, and other substances can be found here - Kind of inclusions depend on the environment where a biofilm develops

Cilia

- Motile and either move the cell or move substances over or around the cell - Protozoans use cilia to collect food particles and for locomotion - (Animals) move fluid, mucus, or cells over their surface - Can either be motile, constantly beating in one direction, or nonmotile, nonbearing sensors

Peripheral proteins

- Partially embedded on one side of the membrane

Microvilli

- Plasma membrane extensions on the surface of eukaryotic cells - Occur in groups on the surface of absorptive and secretory epithelial cells - Increase the surface area of cells to facilitate absorption and secretion

Glycolipids

- Protect, insulate, and serve as a receptor-binding site

Peptidoglycan

- Strength of the cell - Mixed polymer of hexose sugars cross-linked by short peptide fragments - Provide the basis for Gram staining, dividing bacteria into gram-positive and gram-negative organisms

Bacterial mobility

- The thrust by which the flagella propel the bacterial cel is produced by either clockwise or counterclockwise rotation of the basal body driven by energy from a proton-motive force - Movements are referred t was runs (swims) or tumbles

Bacterial flagella

- Used for movement - Long filament - A hook located at the end of the filament - A basal body to which the hook is anchored - Immunogenic - Represent a group of antigens called the *H antigens*

How biofilms form

1. First colony adheres to surface by van der Waal forces 2. Organisms anchor themselves permanently via adhesion molecules 3. Organisms provide more adhesion sites for incoming cells 4. Matrix of biofilm formed 5. Matrix grows-- recruitment and cell division

Lophotrichous

cluster of flagella at one or both ends

Amphitrichous

flagella at both poles of the cell

Peritrichous

flagella distributed over the entire cell

Monotrichous

single flagellum