A peptide synthesised by the reactions of one molecule each of glycine, leucine, aspartic acid and h

Q: Why is the formula $n - 1$ and not just $n$?

Think of a train with $n$ carriages. To connect them all in a single line, you only need couplers *between* the carriages. The first and last carriages don't need an extra coupler on their outer ends, which is why it's always $n - 1$.

Q: Does the specific type of amino acid change the number of bonds?

No, the number of peptide bonds depends entirely on the *quantity* of amino acids in the chain, not their chemical identity. Whether it's glycine or histidine, each connection still requires exactly one bond.

Q: What if the peptide chain forms a closed loop?

Excellent question! If the linear chain loops back and the first amino acid bonds with the last one, an additional peptide bond is formed. In a cyclic peptide, the number of bonds equals $n$.

Q: How many water molecules are released in this reaction?

Since one water molecule is eliminated for every peptide bond formed, the number of water molecules released is exactly equal to the number of peptide bonds. Here, $3$ water molecules are released.

Q: Is a tetrapeptide considered a protein?

Not quite. While both are made of amino acids, peptides are generally short chains (usually fewer than 50 amino acids). Proteins are much larger, complex molecules that fold into specific 3D structures.

Question

A peptide synthesised by the reactions of one molecule each of glycine, leucine, aspartic acid and histidine will have ......... peptide linkages.

Sigma Percentile · Accepted Answer

### The Building Blocks of Life

Imagine you are playing with a set of molecular Lego blocks. In the world of biochemistry, these blocks are called amino acids.

Our problem gives us exactly four of these unique blocks: glycine, leucine, aspartic acid, and histidine.

When these amino acids link together, they form a chain known as a peptide. Because there are four amino acids involved, the resulting molecule is specifically called a **tetrapeptide**.

### The Condensation Reaction

So, how do these blocks actually snap together?

The magic happens through a chemical process called a condensation reaction. The carboxyl group ($-COOH$) of one amino acid reacts with the amino group ($-NH_2$) of the adjacent amino acid.

During this handshake, a water molecule ($H_2O$) is eliminated, and a strong covalent bond is forged. This specific connection is what we call a **peptide linkage** or peptide bond.

### The Master Formula

Now, let's think about the geometry of a linear chain.

If you have two blocks, you only need one link to connect them. If you add a third block, you need a second link.

We can easily generalize this pattern. For any linear sequence of $n$ amino acids, the number of peptide bonds required to hold them together will always be **$n - 1$**.

### Final Calculation

Let's bring this back to our specific question.

We have four amino acids, which means $n = 4$.

Substituting this into our master formula, we calculate the number of peptide linkages as $4 - 1$.

This simple arithmetic gives us our final answer. There are exactly **$3$** peptide linkages in this tetrapeptide.

Animated Solution for Chemistry - Organic Chemistry: A peptide synthesised by the reactions of one molecule each of glycine, leucine, aspartic acid and histidine will have ......... peptide linkages.

Enter Numerical Value:

Visualized Solution

Given Amino Acids

Peptide Bond Formation

Substituting the Values

Calculation

Final Answer

Food for Thought

The Sigma Insight: Biomolecules

The Building Blocks of Life

The Condensation Reaction

The Master Formula

Final Calculation

Similar Questions

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