Problem 1
On a per-carbon basis, where does the largest amount of biologically available energy in triacylglycerols reside: in the fatty acid portions or in the glycerol portion? Indicate how knowledge of the chemical structure of triacylglycerols provides the answer.
Problem 2
Effect of PDE Inhibitor on Adipocytes How would the addition of a cAMP phosphodiesterase (PDE) inhibitor affect the response of an adipocyte to epinephrine?
Problem 3
The activation of free palmitate to its coenzyme A derivative (palmitoyl-CoA) in the cytosol occurs before it can be oxidized in the mitochondrion. After adding palmitate and \(\left[{ }^{14} \mathrm{C}\right]\) coenzyme A to a liver homogenate, you find palmitoyl-CoA isolated from the cytosolic fraction is radioactive, but that isolated from the mitochondrial fraction is not. Explain.
Problem 4
What changes in metabolic pattern would result from a mutation in the muscle carnitine acyltransferase 1 in which the mutant protein has lost its affinity for malonyl-CoA but not its catalytic activity?
Problem 5
An individual developed a condition characterized by progressive muscular weakness and aching muscle cramps. The symptoms were aggravated by fasting, exercise, and a high-fat diet. An homogenate of a skeletal muscle specimen from the patient oxidized added oleate more slowly than did control homogenates consisting of muscle specimens from healthy individuals. When the pathologist added carnitine to the patient's muscle homogenate, the rate of oleate oxidation equaled that in the control homogenates. Based on these results, the attending physician diagnosed the patient as having a carnitine deficiency. a. Why did added carnitine increase the rate of oleate oxidation in the patient's muscle homogenate? b. Why did fasting, exercise, and a high-fat diet aggravate the patient's symptoms? c. Suggest two possible reasons for the deficiency of muscle carnitine in this individual.
Problem 6
Triacylglycerols, with their hydrocarbon-like fatty acids, have the highest energy content of the major nutrients. a. If \(15 \%\) of the body mass of a \(70.0 \mathrm{~kg}\) adult consists of triacylglycerols, what is the total available fuel reserve, in both kilojoules and kilocalories, in the form of triacylglycerols? Recall that \(1.00 \mathrm{kcal}=4.18 \mathrm{~kJ}\). b. If the basal energy requirement is approximately \(8,400 \mathrm{~kJ} /\) day \((2,000 \mathrm{kcal} /\) day \()\), how long could this person survive if the oxidation of fatty acids stored as triacylglycerols were the only source of energy? c. What would be the weight loss in pounds per day under such starvation conditions \((1 \mathrm{lb}=0.454 \mathrm{~kg})\) ?
Problem 8
How many cycles of \(\beta\) oxidation are required for the complete oxidation of activated oleic acid, \(18: 1\left(\Delta^{9}\right)\) ?
Problem 10
What is the structure of the partially oxidized fatty acyl group that is formed when oleic acid, \(18: 1\left(\Delta^{9}\right)\), has undergone three cycles of \(\beta\) oxidation? What are the next two steps in the continued oxidation of this intermediate?
Problem 11
What are the direct products of \(\beta\) oxidation of a fully saturated, straight-chain fatty acid of 11 carbons?
Problem 12
An investigator adds palmitate uniformly labeled with tritium \(\left({ }^{3} \mathrm{H}\right)\) to a specific activity of \(2.48 \times 10^{8}\) counts per minute \((\mathrm{cpm})\) per micromole of palmitate to a mitochondrial preparation that oxidizes it to acetyl-CoA. She then isolates the acetyl-CoA and hydrolyzes it to acetate. The specific activity of the isolated acetate is \(1.00 \times 10^{7} \mathrm{cpm} / \mu \mathrm{mol}\). Is this result consistent with the \(\beta\) oxidation pathway? Explain. What is the final fate of the removed tritium? (Note: Specific activity is a measure of the degree of labeling with a radioactive tracer expressed as radioactivity per unit mass. In a uniformly labeled compound, all atoms of a given type are labeled.)
