Q.Assertion (A): Glycine must be taken through diet.
Reason (R): It is an essential amino acid.

The key idea here is the classification of amino acids into essential (must be obtained from diet because the body cannot synthesise them) and non-essential (can be synthesised by the body). …

1. Understanding the terms

First, recall what "essential" and "non-essential" mean for amino acids in human nutrition.

• Essential amino acids cannot be synthesised by the body at all, or not in sufficient amounts, so they must come from the diet.
• Non-essential amino acids can be synthesised by the body from other compounds, so they do not need to be taken through diet under normal conditions.

Glycine is the simplest amino acid. The body can make it from serine (another amino acid) or from choline and other precursors. It is not essential.

2. Analysing the Assertion (A)

Assertion (A): "Glycine must be taken through diet."

Since glycine is non-essential, the body can synthesise it. Therefore, it does not have to be taken through diet. The assertion is false.

3. Analysing the Reason (R)

Reason (R): "It is an essential amino acid."

This directly contradicts the biological fact. Glycine is non-essential. The reason is false.

4. Evaluating the options

| Option | A (Assertion) | R (Reason) | R explains A? |

|--------|---------------|------------|---------------| …

Concept: Essential vs Non-Essential Amino Acids

Method: Fact-Check & Causal Link Test

Steps:

1. Identify the classification of glycine

   • Glycine is a non-essential (dispensable) amino acid because the human body can synthesise it from other compounds (e.g., serine and threonine).
   • Essential amino acids (e.g., lysine, methionine) cannot be synthesised and must come from diet.

2. Check Assertion (A):

   • “Glycine must be taken through diet.”
   • Since glycine is non-essential, the body can make it — A is false.

3. Check Reason (R): …

Here’s a breakdown of the common mistakes students make on this Assertion-Reason question and how to avoid each.

The Correct Answer First

• Assertion (A): Glycine must be taken through diet. → False
• Reason (R): It is an essential amino acid. → False
• Correct option: (D) Both A and R are false.

Common Mistake #1: Thinking glycine is essential

What students do wrong:

They assume that because the body needs glycine for many functions (collagen synthesis, neurotransmitter production), it must come from food. They confuse “important” with “essential.”

How to avoid:

Remember the definition: Essential amino acids cannot be synthesized by the human body and must come from diet. Non-essential amino acids (like glycine) can be synthesized from other compounds.

• Key fact: The human body can make glycine from serine (another amino acid) and from choline.
• Mnemonic: “Essential = Eat required.” If the body can make it, it’s not essential.

Common Mistake #2: Confusing “essential” with “conditionally essential”

What students do wrong:

Some students recall that under certain conditions (e.g., pregnancy, severe illness, prematurity), glycine may become “conditionally essential.” They then mark the Reason as true.

How to avoid:

The question asks about the standard, healthy adult condition. In standard biochemistry:

• Essential amino acids (9 total): Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine.
• Glycine is NOT on this list.
• “Conditionally essential” is a special case, not the general rule. Unless the question explicitly mentions a specific condition, assume the normal state.

Common Mistake #3: Misreading the Assertion-Reason logic

What students do wrong:

Even if a student knows glycine is non-essential, they might still pick option (C) — “A is true but R is false” — because they think the Assertion is correct (glycine must be taken through diet) and only the Reason is wrong.

How to avoid:

Read the Assertion carefully: “Glycine must be taken through diet.”

• If glycine is non-essential, the body does not must take it from diet. The word “must” makes the Assertion false.
• Tip: In Assertion-Reason questions, watch for absolute words like “must,” “always,” “never.” They often signal a false statement unless the fact is truly universal.

Common Mistake #4: Forgetting the list of essential amino acids

What students do wrong:

Students memorize the list incorrectly or incompletely. They might think glycine is essential because it sounds similar to “glycogen” or because they confuse it with another amino acid.

How to avoid: …