HISTOLOGY-Lecture 1-Cell Membrane

• 1. maintain structural integrity of cell
• 2. semipermeability – controls what get in/out
• 3. regulates cell-cell interactions
• 4. recognition –receptors/antigens/foreign,altered cells
• 5. interface between cytoplasm & external milieu
• 6. establish transport systems for molecules
• 7. transduce extracellular signals -> intracellularly

unit membrane – fluid mosaic model

• phospholipid structure
• leaflet structure
• glycocalyx (cell coat)

increases fluidity

hydrophilic head composed of (1) + nitrogenousgroup glycerol

• phosphategroup
• 2 hydrophobic glycerol tails composed of fatty acyl tails

• biphospholipid (unit membrane)
• a)inner leaflet - cytoplasm - P-face – outer surface
• b)outer leaflet - extracellular - E-face – inner surface
• embedded
• integral (transmembrane) proteins span the membrane
• hydrophilic AA – in/out
• hydrophobic AA – within
• peripheral multipass proteins on the cytoplasmic side of membrane
• cholesterol
• maintain integrity of membrane by increasing and decreasing fluidity
• involved in cell signaling

carbohydrate chains that coat cell surface

• glycoprotein -carbohydrate
• chains attached to transmembrane protein

glycolipid - carbohydrate chains attached to phospholipid molecule

• provides protection from
• a) inappropriate proteins
• b) chemical injury
• c) physical injury
• d) cell-cell recognition
• e) adhesion

carbohydrate chains attached to phospholipid molecule

carbohydrate chains attached to transmembrane protein

maintains integrity of membrane by increasing and decreasing fluidityinvolved in cell signaling

• span the membrane
• hydrophilic amino acid – in/out
• hydrophobic amino acid – within
• peripheral multipass proteins on the cytoplasmic side of membrane