​Slime Layer

• term used when the glycocalyx is unorganized and loosely attached to the cell wall

​The flagella may be:

• ​Peritrichous - distributed over the entire cell

​

• ​Polar

  • ​Monotrichous - single flagella at one pole

  • ​Lophotrichous - a tuft of flagella at one pole

  • ​Amphitrichous - flagella at both poles of the cell

• ​*Atrichous - bacteria with no flagella​

​Taxis

• ​movement of a bacterium toward or away from a stimulus

​

• ​stimulus may be:

​ - chemicals (chemotaxis)

​ - light (phototaxis)

​

• when signal is positive, it moves toward the stimulus, when signal is negative, it moves away from the stimulus

​Cell Walls of Prokaryotes

• ​Gram positive - thick peptidoglycan and teichoic acids

​

• ​Gram negative - thin peptidoglycan and outer membrane

  • ​Outer membrane consists of:

    • Lipopolysaccharide (LPS) - lipid A, core polysaccharide, O polysaccharide

    • ​Lipoproteins

    • ​Phospholipids

​

​

​Ribosomes

• ​Prokaryotes (70S)

  • 50S subunit - 2 molecules of rRNA

  • 30S subunit - 1 molecule of rRNA​

• Eukaryotes (80)

  • ​larger and denser

  • ​consists of:

    • ​60S subunit - 3 molecules of rRNA

    • ​40S subunit - 1 molecule of rRNA

​Pili

• ​longer than fimbria, usually only one or two per cell

​

• ​conjugation pili - called F+ cell, binds to the receptors on the surface of another bacterium for DNA transfer

Osmosis​

• ​water pass through the membrane thru simple diffusion and aquaporins

​

• osmotic pressure - the pressure required to stop the flow of water across a semipermeable membrane

• ​3 kinds of osmotic solutions:

  • ​isotonic solution

  • ​Hypotonic solution

  • ​Hypertonic solution

​The Cytoskeleton is composed of

• microtubules - cylinder

​

• microfilaments (actin filaments) - small rods

​

• intermediate fibers​ - small rods

​

• function: ​provides support, shape, and assistance in transporting substances through the cell

• ​cytoplasmic streaming - movement of cytoplasm from one part of the cell to another to distribute nutrients; absent in prokaryotes

​Cell Walls of Eukaryotes

• ​Algae - contains cellulose

• ​Some fungi - contains chitin (main structural component of the exoskeleton of crustaceans and insects); also contains cellulose

• ​Yeasts - contain polysaccharides - glucan and mannan

• ​Protozoa do not have typical cell wall but have a flexible outer protein - pellicle

• ​Other eukaryotic cells may also be covered by a glycocalyx

  • ​glycoproteins - carbohydrates + proteins

  • glycolipids - carbohydrates + lipids

​3 Types of Endocytosis

• ​Phagocytosis - cellular projections called psuedopods engulf particles and bring them into the cell; used by WBC to destroy bacteria and foreign substances

​

• Pinocytosis - plasma membrane folds inward, bringing extracellular fluid into the cell

​

• ​Receptor-mediated endocytosis - substances (ligands) bind to receptors in the membrane; one way by which viruses enter