Membrane Structure and Function Chapter 4 Membrane Structure and Function

Phospholipid - amphipathic molecule http://www.youtube.com/watch?v=ULR79TiUj80&feature=player_embedded

Membrane Lipids - phospholipid & cholesterol Membrane Proteins - integral & peripheral

Why don't phospholipid molecules flip laterally?? FLUID due to lipid content unsaturated fats = more fluidity hydrocarbon tails wiggle; move laterally Why don't phospholipid molecules flip laterally?? cholesterol keeps membrane from freezing at decreased temperatures stiffens the membrane at increased temperatures

MOSAIC due to protein content number and types of proteins vary proteins in no set position

Carbohydrates glycocalyx protection facilitates adhesion between cells glycolipids & glycoproteins only occur on outside surface glycocalyx protection facilitates adhesion between cells reception of signaling molecules cell-to-cell recognition

Aquaporins

physical process due to the random motion of particles DIFFUSION physical process due to the 
random motion of particles

OSMOSIS water moves from an area of HIGH water 
concentration (low solute concentration) to an 
area of LOW water concentration (high solute 
concentration)

Tonicity - the ability of a solution to cause a cell to gain or lose water Osmotic Pressure - measure of difference in solute concentrations; force needed to stop 
osmotic flow Hydrostatic Pressure - pressure of the cytoplasm pushing against the plasma 
membrane

crenation cytolysis turgor pressure plasmolysis

Maintaining Osmotic Balance http://www.youtube.com/watch?v=4z98WIeNtjM

Active Transport needs ATP moves UP the concentration gradient uses highly selective protein carriers

http://www.youtube.com/watch?v=GTHWig1vOnY

Cotransport

Endocytosis and Exocytosis

Exocytosis vesicle fuses with plasma membrane = secretion Plants - export materials to construct cell wall Animals - secrete hormone, neurotransmitters and digestive enzymes

Endocytosis take in substances by vesicle formation viruses, food, another cell, liquid A is a bacterium B is a WBC

EXTRACELLULAR MATRIX meshwork of proteins and polysaccharides collagen resists stretching elastin gives resilience fibronectin (adhesive) binds to integrin integrin makes contact with cytoskeleton - plays role in cell signaling proteoglycans help resist compression; play role in cell signaling

CELL JUNCTIONS allows coordination of cells adhesive junctions attach adjacent cells tight junctions plasma membrane proteins attach to each 
other gap junction allows cells to communicate

Plasmodesmata pass through cell wall allows water and small solutes to pass freely