Which of the following is the precursor of adrenaline and noradrenaline?
**Core Concept**
The question tests the understanding of catecholamine synthesis, specifically the precursors of adrenaline (epinephrine) and noradrenaline (norepinephrine). Catecholamines are a group of neurotransmitters derived from the amino acid tyrosine.
**Why the Correct Answer is Right**
The correct answer is tyrosine, which is converted into L-DOPA by the enzyme tyrosine hydroxylase. L-DOPA is then decarboxylated to form dopamine, which is further converted into noradrenaline by the enzyme dopamine beta-hydroxylase. Noradrenaline can then be converted into adrenaline by the enzyme phenylethanolamine N-methyltransferase (PNMT). This sequential conversion of tyrosine to adrenaline and noradrenaline is a crucial aspect of the catecholamine synthesis pathway.
**Why Each Wrong Option is Incorrect**
**Option A:** L-DOPA - While L-DOPA is an intermediate in the catecholamine synthesis pathway, it is not the precursor of adrenaline and noradrenaline.
**Option B:** Dopamine - Dopamine is an intermediate in the catecholamine synthesis pathway, but it is not the precursor of adrenaline and noradrenaline.
**Option C:** Tyramine - Tyramine is a monoamine derived from tyrosine, but it is not directly involved in the synthesis of adrenaline and noradrenaline.
**Clinical Pearl / High-Yield Fact**
Tyrosine is an essential amino acid, meaning it cannot be synthesized by the human body and must be obtained through dietary sources. Deficiencies in tyrosine can lead to impaired catecholamine synthesis, which can have significant clinical consequences.
**Correct Answer: C. Tyrosine**