PLE Physio Part 1| 447 questions| with complete solutions

cell membrane phospholipids outer vs inner leaflets Outer Leaflet: C-E-Sphi PhospatidylCholine, PhosphatidylEthanolamine, Sphingomyelin Inner Leaflet: S-I PhosphatidylSerine, PhosphatidylInositol cell membrane major lipoprotein source of cholesterol LDL INTERCELLULLAR STRUCTURES Disk-shaped; For tight intercellular adhesion found in?? Macula Adherens (Desmosomes) think STAPLER wires! epithelium INTERCELLULLAR STRUCTURES • Ring-shaped • increases surface area for contact found in? Zonula Adherens • Epithelial & endothelial cells • Intercalated disks of cardiac muscles Equivalent in cardiomyocytes is Fascia Adherens (ribbon-like patterns; doesn't completely enclose cell) Barrier to movement of proteins across membranes; divides cell into apical and basolateral side Zonula Occludens (Tight Junctions) Leaky: PCT, Jejunum Tight: CD, terminal Colon, BBB Transcellular Transport vs Paracellular Transport Transcellular Transport: movement across apical and basolateral sides Paracellular Transport: movement through TIGHT JUNCTIONS (aka zonula occludens) bridge for sharing of small molecules between cells; For rapid intercellular communication found in?? functional unit?? Gap Junctions Cardiac and unitary smooth muscles ** they enable the cells to contract together as one. When you hear gap junctions, think SYNCITIUM - the ability of muscle cells to contract together as one. Functional Unit: ConneXON (its Subunit: ConneXIN) The low-resistance pathways between myocardial cells that allow for the spread of action potentials are the (A) gap junctions (B) T tubules (C) sarcoplasmic reticulum (SR) (D) intercalated disks (E) mitochondria gap junctions transport of Oxygen, Nitrogen, CO2 across the cell is via? others that move via this? SIMPLE DIFFUSION alcohol, anesthetic drugs, lipid hormones (STEROID HORMONES aka aldosterone, sex hormones) most important characteristic of hydrophobic hormones that governs diffusability across cell membrane Lipid Solubility Which of the following will double the permeability of a solute in a lipid bilayer? (A) Doubling the molecular radius of the solute (B) Doubling the oil/water partition coefficient of the solute (C) Doubling the thickness of the bilayer (D) Doubling the concentration difference of the solute across the bilayer Doubling the oil/water partition coefficient of the solute Solutions A and B are separated by a membrane that is permeable to urea. Solution A is 10 mM urea, and solution B is 5 mM urea. If the concentration of urea in solution A is doubled, the flux of urea across the membrane will (A) double (B) triple (C) be unchanged (D) decrease to one-half (E) decrease to one-third triple For the guide question above: J1 = PA (C1-C2) =PA (10-5) = 5 J2 = PA (C1-C2) = PA (20-5) = 15 J2 is 3x more than J1. Kaya "triple" yung sagot. properties of Carrier-Mediated Transport (3) S-S-C - stereospecificity, saturation and competition ay shape lang na pwedeng gumamit ng carrier protein (stereospecificity), limited and number ng carrier protein (saturation), at pwedeng magkaroon ng competition for the carrier proteins (competition: parang "Trip to Jerusalem"). simple vs facilitated diffusion: which is faster at low concentration? at high concentrations? At low-solute concentrations: Facilitated Diffusion is faster than Simple diffusion (because FD involves carrier proteins, which makes it go faster, analogous to a person riding a fast car) At high-solute concentrations: Facilitated Diffusion is slower than Simple Diffusion (because FD exhibits saturation and transport maximum (basically a speed limit), unlike SD) GLUT transporters found where?? • GLUT 1: BBB • GLUT 2: Liver, Pancreas, Basement Membrane of SI • GLUT 3: Neurons • GLUT 4: Muscles, Adipose • GLUT 5: for fructose transport from SI lumen to SI cell SGLT 1 and 2 location SGLT-1: SI SGLT-2: Kidneys Think of it this way: you have 1 Intestine, but you have 2 kidneys: SGLT-1 and SGLT-2. Which of the following characteristics is shared by simple and facilitated diffusion of glucose? (A) Occurs down an electrochemical gradient (B) Is saturable (C) Requires metabolic energy (D) Is inhibited by the presence of galactose (E) Requires a Na+ gradient Occurs down an electrochemical gradient Transport of D- and L-glucose proceeds at the same rate down an electrochemical gradient by which of the following processes? (A) Simple diffusion (B) Facilitated diffusion (C) Primary active transport (D) Cotransport (E) Countertransport Simple diffusion Glucose is supposed to be transported via carrier-mediated means. Dapat may stereospecificity, so normally hindi same rate and transport ng D-glucose at L-glucose. Pag same lang rate of transport ng D-glucose and L-glucose, ibig sabihin hindi siya carrier-mediated - simple diffusion na siya. Ingat, this is a tricky question since the transport of D-glucose and L-glucose is not through simple diffusion in real life.