What prohibits lipids from being a readily available energy source? a. fat must be broken down into fatty acids before being converted to glucose. b. lipids are structural components, so they are a last-resort energy source. c. lipids are only used to create enzymes, hormones, and antibodies. d. the conversion of fat to glucose is controlled by insulin.

The option A. is true. Fat must be broken dwon into fatty acids before being converted to glucose. The metobolism converts glucose into energy, then if the food is not in the form of glucose, it will not be an energy source readily available. Lipids (fats) are triglecerid molecules (molefcules with three fatty acids) and the metabolism must convert these fatty acids into glucose before being able to provide energy.