Which one of the following statements is not correct regarding the amino acid, tyrosine, present in protein rich foods?

Tyrosine is a non-essential amino acid the body makes from phenylalanine, and it is found in dairy, eggs, meat, fish and soy. Its key role is as the precursor of dopamine, norepinephrine and epinephrine, which regulate alertness, mood and the stress response, and of the thyroid hormones T3 and T4 that govern metabolic rate.

Checking each option against this:

• A (energy): Thyroid hormones and catecholamines raise metabolic activity and alertness, so this is correct.
• B (stress): Under stress, the body makes catecholamines from tyrosine, which helps it respond. This is correct.
• C (depression): Low dopamine and noradrenaline are linked to depression, and tyrosine has been studied for mood support. This is correct.
• D (free radicals): This is the incorrect statement. Antioxidant defence comes mainly from glutathione (built from cysteine, glycine and glutamate), vitamins C and E, and enzymes such as SOD and catalase. Tyrosine is not established as a free-radical scavenger that protects against ageing.

Mains angle: the link between diet, neurotransmitter biology and mental well-being comes up in questions on nutrition and public health.

Trap: Aspirants assume every amino acid mentioned in a health context is an antioxidant. Keep precursor roles and antioxidant roles separate.