Date 20-1b BIOL2220 F18 Exam I Test Corrections Rease raad questions ENTIRELY. Y

Question

Date 20-1b BIOL2220 F18 Exam I Test Corrections Rease raad questions ENTIRELY. You are being graled on your reasoning and expianations move so than our cormect awers Be sure to cxplnin your answers clearly and concisely other eplthelial Uissue in humans. The ion channel is lgand-gated and transports chloride lons from the cytopasm to the outside of cells. The ligand responsible for opening the channel is ATP, and when ATP is hydrolyzed, the channel closes. This is a very unique ion channel, as it is not typical for ATP to regulate a channel. Number 1-7 should not be overy comgwicated. Number 8-13 require more ana/ytical thinking. 1. Is chloride moving with or against its electrochemical gradient? You should be able to answer this simply because you know the type of transport protein we are studying (ion channel) 2. Based on your answer to #1, does the transport of chloride ions release or require energy? mre /.r needeo/rb n, e/, a nnz /)or//7//aw 3. Draw out this scenario, showing both before (on the left) and after (on the right) channel opening. Use the symbol to represent chioride ions (2 have been drawn on elther side of the membrane to get you started. On the left side, place 10 chloride ions on the side of the membrane where the concentration is higher and 2 chloride ions where the concentration Is lower. Draw an arrow to indicate the direction lons will flow through the channel. On the right side, assume that the chloride concentration gradlent has reached equilibrium (ignore any voltage gradient here). Before open Chloride nnel After ope Chloride *00 .-k Inside cell Inside cell watcr e Outside cell Outside cell 4. Why cant chloride ions cross the phospholipid bilayer without the channel? Charged ions cannd pemrae thu au mempiane Channels necele efin oelt

Explanation / Answer

out of , increases, low, lower, low, lower.

Opening the channel will allow movement of chloride ions down its electrochemical gradient from inside to outside of the cells. When chloride moves outside the cells, the concentration of ions outside the cell will increase.. In osmosis water moves from lower to high concentration of solute( in this case chloride) therefore water levels will increase outside cells.

If chloride cannot move through the channel or the channel cannot bind ATP then chloride concentration will rise inside and lower outside cells. ATP binding opens the channel and if it cannot bind ATP it will not open and chloride would not move outside. When chloride concentration rises inside cell, water will move from outside (low) to inside (high) and water levels will be lower outside the cell.

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