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BPK 205 Lecture Notes - Lecture 3: Resting Potential, Membrane Potential, Fluid Compartments

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emeraldlion986
25 Sep 2017
School
Simon Fraser University
Department
Biomedical Physio & Kines
Course
BPK 205
Professor
Nadine Wicks

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Document Summary

Discuss the disequilibrium across cell membranes in the context of. Channels and transporters alter membrane permeability for the specific molecule that they conduct. K: a simple phospholipid membrane is impermeable to k+ because it is a polar charged atom. If we insert a k+ channel into the membrane, the membrane becomes permeable to k+, which can now flow along its electrochemical gradient. Intracellular and extracellular environments are in electrical and chemical disequilibrium (which is critical to physiological function) Many of the solutes in the body are ions: they carry a net electrical charge, ex. Lactate, pyruvate, phosphate, hco3-, k+, cl-, ca2+, na+, proteins, etc. Millimolar concentrations of selected solutes in icf and ecf. 115. 0: proteins -> made inside the cell and often don"t leave (they are very large molecules, net negative charge inside the cell -> there are more negative molecules inside the cell.

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Related Questions

1 Which of the following statements is false?

(a) CO2 and O2 can diffuse freely across the cell membranes.

(b) The differences in permeability between artificial lipid bilayers and cell membranes arise from variations in phospholipid content.

(c) Direction of passive transport of molecules across membrane is controlled by osmosis and electrochemical gradient.

(d) Cells expend energy in the form of ATP hydrolysis to maintain ion concentrations that differ from those found outside the cell.

2 Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant inside a typical mammalian cell?

(a) Na+

(b) K+

(c) Ca2+

(d) Cl–

3 Pumps are transporters that are able to harness energy provided by other components in the cells and drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called _____________.

(a) active transport.

(b) free diffusion.

(c) positive diffusion.

(d) passive transport.

Cellular biology answer check. please check if my answers arecorrect or not.

1) The concentration of ions inside a cell is the same as theirconcentration outside of the cell. True or false? (i chose falsesince having equilibrium inside a cell is bad)

2) Membrane transport proteins...

a)...transport membrane potentials between cells
b) ...transport membranes from the ER to the Golgi
c) ...are made up of phospholipids
d) ...transport molecules across membranes

i chose d

3)The electrochemical gradienttakes into account:

a) The concentration of solutes on either side of themembrane.
b) The overall charge on either side of the membrane.
c) Both of these.

i chose C. (although i am sure that overall charge matters, Iwasn't sure if concentration of solutes are taken account.)

4) If no energywere expended by an animal cell:

a) Both gradients would be depleted
b)The K+ gradient would maintain itself.
c) None of these
d) The Na+ gradient would maintain itself.

I chose d) mainly because I think Na+ gradient exist in animalcell and not K+ gradient.

5) Which of the following is a true statement aboutactin?

a) Once actin has polymerized, it never depolymerizes.
b) Actin is a transmembrane protein.
c) Actin can form branched networks.
d) Actin filaments are organized into hollow tubes.

I chose c. can't explain why.

6)Ion channels:

a) Form a hydrophobic channel through the membrane
b) Have filters that let sugars through
c) Are selective for particular ions (only the

1) This is a thermodynamics questions

In your body, normal osmolarity of blood serum is just under 0.3 molar. Because cell membranes are permeable to water, the osmolarity of intracellular fluid is approximately equal to that of extracellular fluid (though the intracellular and extracellular composition in terms of specific ions and proteins is quite different). As an aside, measurement of osmolarity of serum is an important clinical test used to check for dehydration or other imbalances of water and electrolytes.

a) In the supplemental information, the osmosis example presented involves sucrose as a solute, but the van't Hoff equation also applies for other solutes. Using this formula (∏ = cRT, where ∏ is the excess pressure), calculate the osmotic pressure associated with 0.3 molar concentration of osmolytic particles (e.g., ions, proteins, or other dissolved particles) in contact with pure water through a semi-permeable membrane at physiological temperature of 310 K. Express your results in atmospheres of pressure (1 atmosphere of pressure is 1.0x105 Pascal, where 1 Pascal is a Newton/m2).

b) A biological cell membrane is a bilayer of phospholipid molecules, only a few nanometers thick, and can basically be thought of much like a soap bubble, except immersed in aqueous solution. If cells are placed in pure water, they often swell and burst in just a few minutes. Explain why this would happen.