Guided reading questions Membrane potentials Please note the page numbers might be slightly different between the eText and the printed version Use the titles subtitles mentioned below to locate the specific text Read the following sections 62 Membrane proteins 64 Passive transport diffusion not including Osmosis 65 66 Active transport 248 Resting membrane potential section 10 3 1 285 Electrophysiology of Neurons section 11 3 1 up to and not including Changes in membrane potential P 62 Membrane proteins see also Fig 3 5 This part will serve as a short introduction to help you understand how ions move into or out of the axolemma 1 Define the following groups of membrane proteins Channels membrane proteins that substances pass through to enter or exit the cell Carriers membrane protein that bind and transport substances into or out of the cell Receptors membrane protein that binds to a ligand to change in it or the cell s conformation P 64 Passive transport diffusion 2 Define the following processes and molecules Simple diffusion substances moving through the lipid bilayer without the use of proteins Facilitated diffusion when a substance diffuses using a transport protein Channel mediated diffusion Carrier mediated diffusion Uniporter protein that transfers a single solute Antiporter protein that transfers two solutes in opposite directions Symporter protein that transfers two solutes in the same direction Skip the Osmosis section Pp 65 66 Active transport 3 Describe in two sentences the following processes Primary active transport Primary active transport uses energy directly to move a solute across the membrane against its concentration gradient Secondary active transport Secondary active transport uses energy indirectly like using the concentration gradient of one solute to move another solute across the membrane 4 Mark the correct answer Ion pumps transport ions a down their concentration gradient b against their concentration gradient 5 True False The direction of ion flow into or out of the cell depends on whether the channel is open or closed 6 The sodium potassium pump is a good example of a molecule that drives sodium and potassium via a active transport mechanism primary secondary The pump is considered an symporter antiporter 7 Since a gradient of sodium a gradient maintained by the sodium potassium pump is required for cotransport of glucose together with sodium we refer to the glucose transport across the membrane as a secondary active transport mechanism 8 What is an electrical potential and how can it produce an electrical current Basically the potential energy in a electrical gradient created by unequal positive and negative ions on either side of membrane voltage is indicated by difference in potential at two points Skip Active transport via vesicles Pp 248 285 Resting membrane potential Electrophysiology of Neurons Start reading from Membrane potentials in our cells 9 Why is the resting membrane potential negative How is it measured check also ConceptBoost on P 248 Due to the accumulation of more sodium ions outside the cell than potassium ions inside the cell 10 Sound is received in the inner ear via cells that are called hair cells Sound waves arriving to the inner ear cause waves in the inner ear fluids The hair cells move their hairs which are actually ion channels upon being hit by the fluid waves As a result the hairs bend and open potassium gated channels allowing potassium ion to flow into the cells later to trigger a neural signal that reaches the brain The hairs of the hair cells act as a ligand gated channels b non gated aka leak channels c mechanically gated channels d voltage gated channels 11 A Na ligand gated channel is typically stimulated by acetylcholine the ligand Would you expect it to be stimulated by epinephrine as well Explain No because the receptor is specific to acetylcholine 12 For the next question explore outside the textbook and find out What is a reversal potential aka Nernst potential or Equilibrium potential The point at which the direction of net current flow reverses is called the reversal potential and is the same as the equilibrium potential What is the reversal potential of K in neurons 88 mV 13 True False The chemical gradient drives K from the cytosol out to the ECF 14 True False The chemical gradient drives Na from the cytosol out to the ECF 15 True False The membrane is equally permeable to all ions