8/14/17 Flashcards
Phosphotidylinositol
Inositol sugar head group
Phosphatidylglyceride
Important for cell signaling, gets phosphorylated and recruits signaling molecules to the cell membrane
5th membrane component
Negative charge
Lectin
Carb binding protein
Lipid belayer asymmetry
Inner is negative
Outer has DPPC and glycolipids
Peripheral proteins
Noncovalently linked to membrane proteins
Removed without detergents, like with pH
Restrictions of lateral diffusion for membrane proteins
Linked to cytosolic or ECM proteins
Linked to peripheral proteins attached to another cell
Barriers of diffusion
Cell cortex
Proteins that support the plasma membrane and can bind at transmembrane proteins
Spectrin for RBCs
Proteoglycans
Glycoproteins with long, I branched amino-containing sugars that have a repeating pattern
Glycocalyx
Outer layer of sugars on cell membrane
Fick’s Law
Net solute Flux is proportional to: area of membrane, solute concentration gradient, solute permeability
Inversely: distance or thickness of membrane
Resting membrane potential
Negative inside and positive outside
Sodium-potassium ATPase
Primary active transport so use ATP
3 Na+ out and 2 K+ in
Symport or co-transport
Secondary active transport
Both solute move in the same direction
Na+ and glucose, glucose go against gradient while Na goes down its own
(Antiport if go opposite ways)
Osmolarity
Total solute conc. In solution
Account for van’t Hoff factor
300 mM for normal cells
Tonicity
Concentration of NONPENETRATING solutes
Na and K are considered nonpenetrating
Functions of vesicular transport
Deliver newly made molecules to destination
Communicate with extra cellular environment
Ingest extracellular particles
Protein coats
Drives vesicles budding
Help pinch the vesicles off their donor membranes and sort proteins to correct to the forming vesicle
Sheds off after formation so can reach target
Clathrin
Coat protein, form triskelia
Clathrin coat process
Cargo binds to cargo receptor molecule, cargoreceptor has adaptin bind to it and then clathrin to the adaption, dynamin cuts off bud and then coat disassembles, cargo receptor binds to direct final location
Docking and fusion of vesicles
Rab protein binds to tethering protein
v-SNARE then binds to t-SNARE to initiate fusion
Covalent modifications in the ER
Formation of Cys Cys disulfide bonds and the addition of lipid membrane anchors
Also initial protein glycosylation
Initial glycosylstion in ER
Oligosaccharides are connected to dolichol of the membrane
Asn adds sugars (N-linked) or Ser/Thr does (O-linked), reaction catalyzed by oligosaccharyl transferase
Lysosome
Molecular degradation
Acidic cuz H+ pump, have acid hydroplanes like nucleases
Targeting of lysosomal hydrolases
Hydrolases have mannose-6 phosphate groups added, move from trans Golgi in clathrin vesicles coated with mannose-6 phosphate receptors
Lysosomal membrane proteins have short signal sequence
Lysosomal storage diseases
Dysfunctional hydrolases or cofactors for them
Hydrolase substrate builds up to toxic levels
Live to 15
Most severe: I-cell (inclusion cell) disease, kinase for mannose-6 phosphate is defective
Types of endocytosis
Phagocytosis: large particles, rearrange actin cytoskeleton for pseudopodia
Pinocytosis:fluid and small molecules, IND or DEP on clathrin, non selective and constitutively active
Receptor-mediated endocytosis: use clathrin
Transcytosis
Receptors (and possibly their bound cargo) from receptor-mediated endocytosis travel across the cell to a different membrane domain
Uptake of LDL Cholesterol
Low density lipoprotein has cholesterol core and a surrounding monolayer
LDL receptor for receptor mediated endocytosis, clathrin vesicle fuse with early endosome
Receptor recycled back to cell membrane, LDL released from receptor and degraded in lysosome to release free cholesterol
Hypercholesterolemia
Mutation in LDL receptor limit uptake of LDL particles
Cholesterol build up in blood and cause atherosclerosis and early cardiovascular disease
