Polarized Epithelial Cells

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Department
Biology
Course
BIO130H1
Professor
Gillian Rowe
Semester
Winter

Description
Cellular Membrane Proteins Integral Proteins Transmembrane Single A Multiple A Beta Barrel Lipid GPI Anchored Helix Helices Anchored Polarity Amphiphilic Amphiphilic -hydrophillic domains -hydrophobic membrane spanning domain (AA side chains NP) Single pass Multi-pass 20-30 Rolled up B Anchored on a) Fatty Acid Lipid Anchored hydrophobic Sheet cytosolic Anchor (Ate) (GPI) AA span -rigid face by an b)Prenyl -synthesis in bilayer -aqueous Pore amphiphilic Anchor (yl) ER(lumen) A helix -ends on cell -anchor surface added by (exoface) cytosolic enzymes, directs it to cytosolic face Example Receptors, Ion Channels Continual intracellular In/Out signnalling Channel Peripheral Peripheral membrane protein attached to a integral protein -bound to either face by non covalent interactions Transporter Proteins Active Transport -Against concentration Gradient -requires energy Coupled Transporters Both examples use Na+ Gradient to move against gradient -2 molcs -eventually it will be exhausted -using energy of 1 molc going therefore: Na+/K+ pump to restore the gradient down gradient to bring other up gradient A)Symporters Eg. Na+, Glucose Symporter -same direction -Na goes down, Glucose goes against gradient -different gradient orientation -cooperative binding leads to conformational changes (state A state B) B)Antiporters Eg. Na+/H+ Exchanger -opposite directions -using free energy stored in Na Gradient to moves H+ out of cell or into -same gradient orientation lysosome -maintain optimal pH levels in cytosol and acidic in lysosome ATP Driven Pumps (ATPases) -thru ATP hydrolysis A) P-Type ATPase (ions) Na+/K+ Pump -phosphorylates itself -both moved against gradient to create Na+ gradient -moves against gradients used to transport glucose into cell, maintain pH &V 1) 2K release 3 Na bind ATP hydrolyzed conformational change ADP released 2) 3 Na released 2K bind release phosphate conformational change -Repeat B) F-Type and V-Type ATPase (proton pump) Structurally related, complete opposites F-Type) ATP Synthase V-Type) H+ Pump -use H+ gradient to drive synthesis of ATP -uses ATP to pump H+ into lysosomes and vacuoles -in mito, chloroplast, bacteria -moves H+ against gradient -H+ moved down gradient and energy gathered C) ABC Transporter -ATP Binding Cassette -each uses 2 ATP eg. multidrug resistence protein -pumps small molecules out of cell -overly expressed in cancer cells Channel Protein (NOT transporter protein) -passive -hydrophillic pore across membrane eg. Ion channels -faster than transporters but weaker -several can pass at a time, more than a transporter 1) Non-Gated: K+ leak channels 2)Gated: chemical/electrical signal required to open a)voltage gated -opens with changes in voltage b)mechanicaly gated -opens when plasma membrane stretched c)Ligand Gated(extracellular) -stimulus molecule from outside to open d)ligand gated(intracellular) -stimulus molecule from inside to open eg. Neurotransmitter opens and flows thru channel and changes membrane potential, opening voltage gated channel Epithelial Tissue Connective Tissue Eg. Intestines, skin Eg, bone, tendon -closely associated -rarely connected -limited ECM (only a thin basal lamina) -plenty of ECM -cytoskeletal filaments: resistance to mechanical -ECM: resistance to mechanical stress stress attached to matrix -attached to each other and the ECM Transporter Proteins Passive Transport -Down concentration gradient -requires no energy Uniporter Eg. GLUT Uniporter (glucose) -one molecule -reversible if gradient changes -down electrochemical gradient Signal Sqn. Position Product N- Terminal No Stop Sqn. -Start sqn cleaved off Secreted Protein (N terminal inside) Stop Sqn -start sqn cleaved off Single Pass Transmembrane -Stop sqn is trans Protein -start sqn cleaved Multipass Another start sqn Internal No Stop Sqn Proteins will check Single pass transmembrane, (N terminal may or neighborin
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