BIPN 100 Lecture Notes - Lecture 3: Membrane Potential, Electrochemical Gradient, Extracellular Fluid

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burgundyfish293

17 Oct 2013

School

UCSD

Department

Biology/Animal Physiol & Neurosc

Course

BIPN 100

Professor

Laurie Smith

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Document Summary

Channel proteins make a hole in the membrane that ions can cross through, making membranes permeable to ions. Channels are specific, they allow only specific ionic species to cross, not allowing other ionic species to cross. Allows ions to leak across the membrane. Pathway: slow movement of potassium out of cell into the extracellular space. Eventually, the concentration of k inside and outside the cell would be the same because potassium would be added to the extracellular fluid. Koutside never equals kinside (unless we die) because there"s another kind of protein in membrane that binds sodium and potassium and translocate the two ions, it pushes potassium into the cell and sodium out of the cell. It is moving the ions against concentration gradients and electrochemical gradients. Energy is added to the system via hydrolysis of atp to move sodium against its electrochemical gradient, keeping concentration inside and outside the cell very stable.

Related Questions

(1) What would be thelikely outcome if an increase in both intracellular sodium ionlevels and extracellular potassium ion levels were tooccur?

A: The Na+-K+ pump would accelerate because it needs to restorethe membrane's resting concentration gradient.

B: The Na+-K+ pump would slow down because it needs to restorethe membrane's concentration gradient.

C: Sodium and Potassium ions would be pumped out of thecell.

D: Sodium and Potassium ions would increase their movement inboth directions across the cell membrane.

(2) Due to the unequal transport of sodium and potassiumions by the Na-K pump, a membrane potential isgenerated.

True or False

(3) If a pump moves 3 positive ions out and 2 positiveions in against their concentration gradients, the membranepotential in the cell will become more positive.

True or False

skyrabbit531

Read the following scenarios and indicate which of the following processes they describe.

11. Sodium molecules move randomly around a solution of sodium chloride in water, frequently colliding with other sodium ions and chloride ions. secondary active transport diffusion osmosis facilitated diffusion primary active transport

12. Sodium ions (Na+) move through sodium channels in a synthetic membrane. primary active transport secondary active transport facilitated diffusion osmosis

13. Water molecules move into the cytosol of a cell placed in a hypotonic solution. primary active transport secondary active transport facilitated diffusion osmosis

14. Water molecules move into the cytosol of a cell placed in pure water. facilitated diffusion osmosis secondary active transport primary active transport

15. Water molecules move out of a cell placed in a hypertonic solution. facilitated diffusion primary active transport secondary active transport osmosis

16. The action of sodium-potassium pumps moves sodium ions (Na+) out of a cell and potassium ions (K+) into a cell. facilitated diffusion secondary active transport osmosis primary active transport

17. Glucose molecules move into cells lining the intestine against their concentration gradient driven by the movement of sodium ions (Na+) into the cells down their concentration gradient. osmosis secondary active transport primary active transport facilitated diffusion

18. A beaker of water is separated by a selectively permeable membrane that allows the passage of water but not ions. A solution of 4% sodium chloride (NaCl) is placed on one side of the membrane and pure water is placed on the other side of the membrane. The solutions are allowed to equilibrate. At this point, which process is going on? facilitated diffusion osmosis secondary active transport primary active transport