A Closer Look At Cell Membranes

 Basically similar in all membranes  Fluid mosaic model  Mixed composition  Lipids not fixed in place, can move

 Phospholipids  Glycolipids  Proteins  Glycoproteins  Sterols

 Polar head, non-polar tail  Majority of membrane  Provides fluidity

 Carbohydrate + Phospholipid  Recognition sites

 Decrease membrane’s fluidity  Developmental signaling  Cholesterol  Hormones

 Glycoprotein = Carbohydrate + Protein  Multiple functions within cell membranes

 Peripheral proteins  Only on surface  Cell receptor sites

 Integral proteins  Within the membrane  Channel/Transport Proteins—allow molecules to pass across Active Na/K transport failure obesity Passive Cystic fibrosis  Adhesion Proteins—connect similar cells into tissues

 Communication Proteins—channels between cells Gap junction  Receptor Proteins—Docks for chemicals that signal cell activities Pygmies  Recognition Proteins—ID self vs. non-self Blood tranfusion Organ transplant

 Selectively permeable  Depends on…  Size  Charge  Polarity  Concentration gradient

 Passive—no energy used  Diffusion—movement of molecules from high to low concentration  Osmosis—movement of WATER from high to low  Concentration gradient  Active—energy used  Movement against gradient  Usually requires carrier molecule

 Endocytosis—creating vesicle to move things into cell  Exocytosis—moving things out of cell by merging vesicle into membrane

 Diffusion  Movement of molecules  High to low  Simple & Facilitated  Lipid solubility

 Osmosis  Movement of water  High to low  Semipermeable membrane  Based on solute

 Isotonic—Same solute concentration in cell & solution  Hypertonic—More solutes in solution than cell  Hypotonic—Less solutes in solution than cell

 Plants  Plasmolysis  Turgor pressure  Animals  Crenation  Lysis

 Requires energy  ATP  Against a gradient  Single movement  Calcium pump  Cotransport  Sodium-potassium pump

 Exocytosis  Movement of things out of cell  Vescicles  Golgi bodies

 Receptor-mediated  Substance binds to receptors, vesicle forms  Phagocytosis—“cell eating”  Engulf food  Pinocytosis—“cell drinking”  Engulf dissolved particles