1) How does the lipid solubility affect the permeability of solute through biological membranes?
2) How does the molecular weight affect the permeability of solute through biological membranes?
3) Define the process of osmosis, osmotic pressure, semipermeable membrane.
4) What is the approximate osmolarity of the extracellular fluid? Of the intracellular fluid?
5) Differentiate the process of diffusion and active transport. Identify the different forms of active transport.
6) Describe the characteristics of protein-mediated transport.
7) Why will inhibition of ATP synthesis by a cell lead eventually to a decrease and, ultimately, cessation in secondary active transport?
8) Explain: if two solutions with different osmolarities are separated by a water-permeable membrane, why will a change occur in the volumes of the two compartments if the membrane is impermeable to the solutes, but no change in volume will occur if the membrane is permeable to the solute?
9) Why patients with diabetes can experience significant changes in blood osmolality?
10) Give some examples of diseases that are related to defects in ion transport across plasma membrane.
11) Describe the significance of rehydration therapy. Why absorption of glucose in lining of intestines increases absorption of sodium and water?
12) Briefly describe the danger of intravenous infusion of hypertonic solutions. How cells can use intracellular mechanisms to prevent loss of water. Use the example of inositol synthesized by brain cells.
13) Explain the difference between osmolality and tonicity. How tonicity can change cell volume? How infusion of hypertonic solution to diabetic patients can affect their cell volumes?
14) Briefly describe the concept of steady state in a regular body cell. What is a role of Na+/K+ – ATPase? How this state can be changed in patients with hypokalemia?
15) What ions are present in highest concentration inside of most body cells? How intracellular concentration of Calcium is regulated?
16) What is a mechanism of digitalis action on cardiac myocytes, knowing that digitalis (digoxin) is used to increase cardiac contractility?
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Cell membrane act as an effective barrier in the transportation of the solute, dissolved substances and various other substances. Membrane are mostly composed of bilayer, where the outer side is hydrophilic in nature and inner portion is hydrophobic in nature. Notably the lipid solubility of the molecules are helpful for passage across the cell membrane, but it opposes large lipid soluble molecule, water soluble molecules and electrically charged molecules with respect to import and export via the cellular membrane. Transport of many crucial and important molecules thus proceeds with the help of intrinsic proteins and is mediated by specific transport system, such as open channel, ionic diffusion and transformation of the molecules.
In general, the molecules, which have lipid solubility, are easier to get diffuse across the cell membrane as they are more permeable. Permeability is a function, which is related to the fatty acids or the long acyl hydrophobic chains of the lipid bilayer. It is thus the permeability of any substance of organic molecules is more important with respect to the passage across the cell membrane (Xiang& Anderson, 1994). Partition coefficient of the molecule is thus one of the important criteria for the conclusion of the permeability related property.
Jermaine Byrant
Nicole Johnson
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