Semi essential amino acids are
**Core Concept**
Semi essential or conditionally essential amino acids are those that can be synthesized by the human body under normal conditions but may become essential during periods of rapid growth, stress, or disease. These amino acids are typically produced from other amino acids and are not typically found in the diet in significant amounts.
**Why the Correct Answer is Right**
The correct answer includes Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine. However, the question is incomplete. Assuming it's about semi-essential amino acids, the correct answer might be Histidine. Histidine is considered semi-essential because it can be synthesized in the body from other amino acids, specifically from the amino acid glutamate. This process occurs primarily in the liver and involves the enzyme histidase.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not available.
* **Option B:** This option is not available.
* **Option C:** This option is not available.
**Clinical Pearl / High-Yield Fact**
Histidine is also a precursor to histamine, a biogenic amine involved in immune responses, allergic reactions, and gastric acid secretion.
**Correct Answer:** A. Histidine.