Chemistry Lecture 11: Lipids

LDL

"bad cholesterol", transports cholesterol to tissues, if too high, deposits plaques in blood vessels

HDL

"good cholesterol", transports cholesterol from tissues to liver for elimination

in terms of their attractive forces, explain why fats are solids but oils are liquids under normal conditions, despite the fact that both are triglycerides

Fats and oils are both triglycerides; however, the large number of cis double bonds in the hydrocarbon tails of oils prevents them from interacting with each other as much as the saturated tails of the fats. More interactions means that the tails move more slowly, becoming more like a solid, forming a fat.

will KCl or (CH3)3N be more soluble in water?

KCl. The ions in KCl dissolve in water through strong ion−dipole interactions, while (CH3)3N interacts with water via dipole-dipole interactions.

in terms of attractive forces, explain why oil and water do not mix

Molecules that "mix" or dissolve in each other are similar in terms of polarity and can participate in the same types of intermolecular forces. Oil is nonpolar and forms only London forces. Water is polar, and while it can form London forces, these are insignificant given that it can also form dipole-dipole attractions and hydrogen bonding. Because oil and water are opposite in terms of polarity and do not have the same intermolecular forces, they cannot interact with each other and do not mix.

will a fatty acid or a fatty acid salt be more soluble in water?

The fatty acid salt is more soluble in water. The salt can form stronger ion−dipole interactions not available to the fatty acid.

oils

liquid, plants, unsaturated, kinked shape (can't stack due to kinked shape, lower surface area, weaker IMF's, lower melting point)

lipids

nonpolar biomolecules -includes triglycerides, phospholipids, cholesterol and other steroids -contain fatty acids or steroid nucleus

cell membrane

semipermeable membrane that separates cell components from the outside -lipid bilayer -polar heads face out, non polar tails face in

fats

solid, animals, saturated, straight shape (can easily stack, larger surface area, stronger IMF's, higher melting point)

lipoproteins

used to transport lipids through the body