1. You create an artificial cell in a test tube. This artificial cell consists o
ID: 42750 • Letter: 1
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1. You create an artificial cell in a test tube. This artificial cell consists of a cytoplasm (i.e. the inside of the cell), a lipid bilayer, and the outside. The cytoplasm contains 150 mM NaCl. whereas the outside solution coiitainsl5 nM NaCl. The only kind of proteins present in the membrane are Cl? ion channels, but they are closed. a. Are any ions flowing across the cell membrane? If so, which ions are flowing and are they flowing inward or outward? b. Is there a membrane potential across the cell membrane? If so, is (lie membrane potential positive on the inside or negative on the inside? c. Are there concentration gradients across the cell membrane? If so, for which ions are there concentration gradients, and are those ions at higher concentrations or lower concentrations inside the cell? Now assume that, all of the sudden, the Cl-channels in the cell membrane open. d. Are any ions flowing across the cell membrane? If so, which ions are flowing and are they flowing inward or outward? e. Is there now a membrane potential across the cell membrane? If so, is the membrane potential positive on the inside or negative on the inside? f. Are there concentration gradients across the cell membrane? If so, for which ions are there concentration gradients, and are those ions at higher concentrations or lower concentrations inside the cell?Explanation / Answer
1. a. Yes, Na+ ions flow across the cell membrane. They are flowing inwards.
b. Yes, membrane potential is present. The membrane potential is positive inside.
c. Yes, there is concentration gradient across the membrane. Sodium ions form concentration gradient, which are present in higher concentration inside the cell.
d. Yes, cl- ions flow outside. They are flowing outside
e. Yes, because the membrane potential is increased due to the outward flow of cl- ions. The membrane potential is more positive on the inside.
f. Yes, there is concentration gradient across the membrane. Sodium ions form concentration gradient, which are present in higher concentration inside the cell.
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