Answer to Question 1
Selenium's bioavailability is high, and its intestinal absorption is not regulated.Once absorbed, selenium circulates in the blood to the body's cells. Some selenium is incorporated into amino acids, which are subsequently used to make selenoprotein molecules. There are at least 14 selenoproteins in the body. One group of enzymatic selenoproteins helps protect against oxidative damage and may protect against certain types of cancer, but more research is required to understand the role of selenium in disease prevention. The kidneys maintain blood selenium concentrations, and excess amounts are simply excreted in the urine. When consumption is high, selenium can also be expelled in the breath, causing a garlicky odor.
Answer to Question 2
Osmosis is the process whereby water molecules move from a region of low solute concentration across a cell membrane to a region of high solute concentration. A solute is a substance (such as a protein or electrolyte) that is dissolved in a fluid. While water molecules can move freely across most cell membranes, solutes generally cannot. A high concentration of solutes generates a force that attracts water, diluting the higher concentration of solutes. Thus, the driving force behind osmosis is the difference in intracellular and extracellular fluids' solute concentrations. The movement of water ceases when the concentration of solutes is the same on both sides of the cell membrane.
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