MCAT Biology Practice Questions the chemical reaction that breaks down all the major macro-molecules - Answer: Hydrolysis What is the strongest type of INTER-molecular bonds? - Answer: Hydrogen bonds are the strongest intermolecular bonds.... diople-dipole bonds are weaker. . . Vander wall bonds are the weakest. Why is water a liquid at high temperatures? - Answer: Hydrogen bonding bonds the water molecules closer together. What is an ampipathic molecule? give an Example. - Answer: A molecule with both hydrophobic and hydrophilic regions. Example: Phospholipids (Phospho=philic,lipid= phobic) What is a lipid? - Answer: A lipid is a biological molecule with low solubility in water. Lipid means fat. Liposuction is fat removal. Peptides are NOT lipids. What are the 6 major groups of lipids? - Answer: 1) fatty acids... the next 3 have a 3 carbon back bone: 2) Tri-glyceride 3) Phospholipids 4) Glycolipids MCAT Biology Practice Questions 5) Steroids 6) Terpenes - A large class of organic compounds. examples: smelly pine oils, beer hops aroma and vitamin A. What is the structure of a Tri-glyceride? - Answer: triglicerides are esters. Composed from 3 carbon glycerol backbone and 3 fatty acid chains dangling. Each carbon chain is attached by an ester bond. What happens if you add water to an ester group in a Tri-glyceride? How is this reaction rate increased? - Answer: Water cleaves the ester bond into an alcohol and a carboxylic/ fatty acid. LIPASES speed are the enzyme that speed this reaction. in terms of water solubility, What is important to know about the longer the carbon chain in a Tri-glyceride when broken down? - Answer: longer carbon chains are less water soluble. In longer chains the polar carboxylic acid are less significant. How soluble is a Shorter chain fatty acids? - Answer: Shorter chain fatty acids are slightly water soluble. explain what is so special about Saturated Fatty Acids........Also, explain the melting point. - Answer: saturated fatty acids have only single, alkane bonds along the carbon chain. They have a straighter chain and have more van der wall forces, and therefor a higher melting point. MCAT Biology Practice Questions explain what is so special about Unsaturated Fatty Acid.... Also, explain the melting point. - Answer: Unsaturated fatty acids have at least one double bond. They are not saturated with Hydrogen. they have a LOWER melting point. At room temperatures unsaturated fatty acids may be oily, like Healthy peanut butter. explain the phospho-lipids structure. Where are phoshpo lipids common? - Answer: Phospholipids are also built on a 3 Carbon backbone. One of the carbon has a Phosphate PO4 group. the other 2 carbons have carbon chains attached by a ester bond. This is the lollypop of the cell membrane. Esters have 2 oxygens