Question

For existence of life, amino acids as ingredient of protein exist mainly in (A) \(l\)-form (B) d-form (C) L-Form (D) D-form

Short answer

The amino acids as ingredients of proteins exist mainly in the \(l\)-form. So, the correct answer is (A) \(l\)-form.

Step-by-step solution

Identify the correct form of amino acids in proteins

In proteins of living organisms, amino acids are predominantly found in the L-form. This means that the correct answer should have "L" or "l" in the option.

Choose the correct option

From the given options, we can see that only option (A) has "l" in it. The other options have either "D" or "d". Therefore, the correct answer is (A). The amino acids as ingredients of proteins exist mainly in: (A) l-form

Key concepts

L-form amino acids

Amino acids are foundational building blocks of proteins, crucial for life's functions. Among the many properties defining these compounds, one important aspect comes from their chiral nature. This chirality refers to the fact that amino acids can exist in different forms that are mirror images of each other, much like our left and right hands.

In the biological context, we're particularly concerned with the L-form. This form is the predominant type found in the proteins of all living organisms. Essentially, this means nearly all amino acids found in proteins twist in the same direction, called the "left"-handed or L-form.

It is intriguing that while both L- and D-forms (the right-handed form) exist, life on Earth has evolved to predominantly use the L-form amino acids in proteins. The reason behind this dominance is not fully understood, but it is universal across nearly all known forms of life.

stereochemistry in biology

Stereochemistry is a fascinating branch of chemistry. It involves studying the spatial arrangement of atoms within molecules. This spatial arrangement plays a crucial role in biological systems, particularly in how molecules like amino acids function.

Amino acids are small organic molecules used by cells to build proteins. They are characterized by having a central carbon atom connected to an amino group, a carboxyl group, a hydrogen atom, and a variable group known as the side chain. This configuration forms a tetrahedral shape around the central carbon, giving rise to chirality.

Understanding the stereochemistry of amino acids is vital because it affects how these molecules interact with enzymes and other cellular components. In enzymes, the active site often demands a specific stereochemical configuration for binding efficiently. This specificity ensures that biochemical reactions are highly selective, often only catalyzing the reaction of molecules with the correct stereochemistry.

D-form versus L-form

To fully appreciate the role of chirality in biology, it's important to understand the differences between D-form and L-form amino acids:

• **D-form amino acids:** These are the mirror image of L-form amino acids, similar to how our right hand is a mirror image of our left hand. While D-amino acids are not common in proteins of living organisms, they are found in some bacteria and in certain naturally occurring antibiotics and peptides.
• **L-form amino acids:** The more biologically prevalent form, L-amino acids are incorporated into proteins by the ribosomal translation process in cells. This form is chosen predominantly over the D-form in nearly all living organisms.

This dominance of L-forms in life highlights an interesting aspect of molecular evolution. One theory suggests that early amino acid synthesis naturally favored the L-form due to the cosmic environment or certain catalytic processes.

Despite the mystery surrounding their predominance, the use of L-form amino acids represents a fundamental characteristic of terrestrial life. Understanding this concept helps us appreciate the nature of biological symmetry and life's reliance on specific molecular forms.