Ethanol CH3CH2OH is miscible in water because it is able to

Ethanol (CH3-CH2-OH) is miscible in water because it is able to form hydrogen bonds with itself and other molecules. However, its structure only allows it to form 1-2 hydrogen bonds. This is one reason why even low concentrations of ethanol in solution are lethal for cells. Based on this information, explain why we can use high concentrations ethanol to precipitate DNA out of solution. Also, describe predict the effects of increasing concentrations of ethanol in (and around) a cell on macro-molecular interactions (i.e. on weak bonds). Finally, it is possible to select for yeast that a tolerant to increased concentrations of ethanol. Give an example of a physiological change in yeast cells that might make them resistant to ethanol.

Solution

1. DNA is a highly polar molecule as a result of which it is highly soluble in water. Due to its high polarity, the electrostatic forces between charged particles is much less in aqueous solution. There is formation of a shell by water molecules around charge particles.

Ethanol is less polar and its addition disrupts the shell formed by water molecule around charged particles. As a result, there is ionic bond formation between phosphate groups of DNA and positively charged ions present in the solution. This causes precipitation of DNA.

2. Ethanol disrups the hydrogen bonds between water molecules. This alters the hydrophilic regions of the plasma membrane, thus altering their structure. There is a resultant dehydration of cells.

3. Upon exposure to ethanol, yeast produces high amounts of monounsaturated fatty acids in cellular lipids. This an be a method of developing ethanol tolerance in some strains of yeast.