PLASMA MEMBRANE The selectively permeable fluid mosaic What

PLASMA MEMBRANE The selectively permeable fluid mosaic

What types of cells have a P. M. ?

FUNCTIONS: FLEXIBLE BARRIER REGULATES PASSAGE IN/OUT OF THE CELL PROTECTION Maintain Homeostasis IDENTIFICATION

CELL ENVIRONMENT Aqueous = watery Intercellular – cytoplasm Extracellular – between cells, fluid environment

REVIEW: Importance of Water is most abundant compound in living things Comprises 70 -95% of most organisms Polar Molecule Universal Solvent

H 2 O is a Polar Molecule

Polar Molecule: Structure & Properties Each molecule has a partial positive & partial negative end Polarity determines how water interacts with other substances Polar & Ionic substances are easily dissolved in H 2 O Nonpolar substances do not dissolve in H 2 O Example: Lipids

New Terminology: Hydrophilic: Hydro = Philic = Hydrophobic: Hydro= Phobic =

MEMBRANE STRUCTURE: Phospholipid Bilayer 2 layers of phospholipids Phosphate head with two fatty acid tails

PHOSPHOLIPIDS

PHOSPHOLIPIDS: STRUCTURE & PROPERTIES PHOSPHATE “HEAD” Polar Hydrophilic Oriented towards outside of cell FATTY ACID “TAIL” Nonpolar Hydorphobic Oriented towards inside of cell

Additional Components:

Additional Components: Proteins External surface: Identification & Protection Inner Surface: Internal support & Flexibility Transport Proteins: Selectively move materials (more info later) Cholesterol: In Eukaryotic organisms Embedded within fatty acid tails Maintains stability of membrane structure

FLUID MOSAIC MODEL

WHY IS IT DESCRIBED THIS WAY? “FLUID” – it interacts with water and is flexible; exhibits some characteristics of a liquid “MOSAIC” – pattern of structures embedded with the membrane; structures are not fixed – can move around Exhibits Flexibility & Resiliency Simultaneously

In Summary: PLASMA MEMBRANE: Flexible, selectively permeable, phospholipid bilayer Provides: Structure & Support Regulation Protection ALL TO MAINTAIN HOMEOSTASIS FOR THE CELL