Please kindly help and explain the concepts...Thank you so much. You create an a
ID: 5012 • Letter: P
Question
Please kindly help and explain the concepts...Thank you so much.You create an artificial cell in a test tube. This artificialcell consists of a cytoplasm, a lipid layer and the outside. Thecytoplasm contains 150mM NaCl and the outside solution contain 15mMNaCl. The only kind of proteins present in the membrane are Cl-ions channels, but they are closed.
Are any ions flowing across the cell membrane? If so, whichions are flowing and are they flowing inward or outward? Are thereany concentration gradient across the cell membrane? If so, forwhich ions?
You create an artificial cell in a test tube. This artificialcell consists of a cytoplasm, a lipid layer and the outside. Thecytoplasm contains 150mM NaCl and the outside solution contain 15mMNaCl. The only kind of proteins present in the membrane are Cl-ions channels, but they are closed.
Are any ions flowing across the cell membrane? If so, whichions are flowing and are they flowing inward or outward? Are thereany concentration gradient across the cell membrane? If so, forwhich ions?
Explanation / Answer
The only ion channels present in the membrane are Cl-channels, but they are closed. Ions cannot pass through the lipidbilayer membrane without an open channel because the are chargedand the inside of the bilayer is nonpolar. There is no membrane potential across the cell membrane. The chargeon each side of the membrane is balanced. On the inside of themembrane, 150mM Na+ is balanced by 150mM Cl–. On the outsideof the membrane 15mM Na+ is balanced by 15mM Cl–. There are concentrations gradients for both Na+ and Cl-. Both Na+and Cl– are at higher concentrations inside the cell.Nowassume that, all of the sudden, the Cl– channels in the cellmembrane open. Cl– ions are flowing outward. The Cl– channels are nowopen so Cl– will move down its concentration gradient. There is a membrane potential that is positive on the inside. SinceCl– ions have moved to the outside of the cell membrane, theNa+ ions inside the cell are no longer balanced by Cl– ions,causing a positive membrane potential inside the cell There are concentrations gradients for both Na+ and Cl–. BothNa+ and Cl– are at higher concentrations inside the cell.Even though the Cl– channels are open, very few ions (~ onemillionth of them) leave the cell before the concentration gradientand electric potential are in equilibrium, so the concentrationgradient of Cl– remains virtually unchanged.