During starvation, which of the following shows the most marked increase in plasma concentration?
**Core Concept**
During starvation, the body undergoes a series of metabolic adaptations to maintain energy homeostasis. This involves the breakdown of stored glycogen, fatty acids, and protein to produce energy. As starvation progresses, the body shifts from relying primarily on glucose for energy to using ketone bodies, produced from fatty acid breakdown, as an alternative energy source.
**Why the Correct Answer is Right**
The most marked increase in plasma concentration during starvation is observed in **B. Ketone bodies**. This is because as glucose stores are depleted, the liver starts to break down fatty acids to produce ketone bodies, such as acetoacetate, beta-hydroxybutyrate, and acetone. These ketone bodies serve as an alternative energy source for the brain, heart, and other tissues. The increase in ketone body production is a hallmark of starvation and is used as a diagnostic indicator of prolonged fasting or starvation.
**Why Each Wrong Option is Incorrect**
**Option A:** Glucose levels actually decrease during starvation as the body's glucose stores are depleted.
**Option C:** Fatty acid levels may increase in the bloodstream during starvation, but they do not show the same marked increase as ketone bodies.
**Clinical Pearl / High-Yield Fact**
In clinical practice, the measurement of ketone bodies in the urine or blood can be used as an indicator of starvation or prolonged fasting. This is particularly useful in assessing the nutritional status of patients, especially in cases of malnutrition or eating disorders.
**Correct Answer:** B. Ketone bodies.