The optically inactive amino acid is

Options

A. Lysine
B. Glysine
C. Arginine
D. Alanine

Answer

To determine the optically inactive amino acid, we need to understand the concept of chirality in amino acids. Here's a step-by-step solution:

### Step 1: Understand Chirality
Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image. A chiral molecule typically has a carbon atom bonded to four different groups, making it asymmetric.

**Hint:** Look for carbon atoms that are bonded to four different substituents to identify chiral centers.

### Step 2: Identify Amino Acids
Amino acids are the building blocks of proteins and generally have a central carbon atom (alpha carbon) bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable side chain (R group).

**Hint:** Recall the general structure of amino acids to identify the components.

### Step 3: Analyze Glycine
Glycine is the simplest amino acid. Its structure is:
- Amino group: -NH2
- Carboxyl group: -COOH
- Hydrogen atom: -H
- Side chain (R group): -H

This means that the alpha carbon of glycine is bonded to two hydrogen atoms and two other groups (the amino and carboxyl groups).

**Hint:** Check the substituents on the alpha carbon of glycine to see if it has four different groups.

### Step 4: Determine Chirality of Glycine
Since the alpha carbon in glycine is attached to two hydrogen atoms, it does not have four different groups. Therefore, it is not chiral and is considered optically inactive.

**Hint:** Remember that a molecule must have four different substituents on its chiral center to be optically active.

### Step 5: Conclusion
Based on the analysis, glycine is the only amino acid that is optically inactive due to the presence of two identical hydrogen atoms attached to its alpha carbon.

**Final Answer:** The optically inactive amino acid is glycine.

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