Question

Sketch the tetrapeptide obtained from four molecules of the \(\alpha\) -amino acid glycine.

Short answer

Answer: The structure of the tetrapeptide obtained from four molecules of glycine is H2N-CH2-CONH-CH2-CONH-CH2-CONH-CH2-COOH. It consists of a linear chain of four glycine molecules connected by three peptide bonds.

Step-by-step solution

Analyzing the structure of glycine

Glycine is an α-amino acid, which means it contains an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (-H), and a side chain, all attached to a central α-carbon atom. The side chain of glycine is a single hydrogen atom, making it the simplest α-amino acid. The structure of glycine can be represented as: H2N-CH2-COOH.

Understanding peptide bond formation

A peptide bond is formed when the amino group of one amino acid molecule reacts with the carboxyl group of another amino acid molecule, releasing a water molecule. This is a condensation reaction that forms a covalent bond between two amino acids, creating a dipeptide. This process can be repeated multiple times, resulting in longer peptide chains.

Sketching the tetrapeptide from four glycine molecules

To sketch the tetrapeptide formed by four molecules of glycine, we need to form three peptide bonds, which will connect the four glycine molecules in a linear chain. Here's the step-by-step process: 1. First glycine molecule: H2N-CH2-COOH 2. Second glycine molecule: H2N-CH2-COOH 3. Form first peptide bond: The amino group of the first glycine molecule reacts with the carboxyl group of the second glycine molecule, releasing a water molecule, and forming the peptide bond: H2N-CH2-CONH-CH2-COOH 4. Third glycine molecule: H2N-CH2-COOH 5. Form second peptide bond: The amino group of the dipeptide reacts with the carboxyl group of the third glycine molecule, forming another peptide bond: H2N-CH2-CONH-CH2-CONH-CH2-COOH 6. Fourth glycine molecule: H2N-CH2-COOH 7. Form third peptide bond: The amino group of the tripeptide reacts with the carboxyl group of the fourth glycine molecule, forming the final peptide bond and the tetrapeptide: H2N-CH2-CONH-CH2-CONH-CH2-CONH-CH2-COOH The resulting tetrapeptide is a linear chain of four glycine molecules connected by three peptide bonds, with the structure H2N-CH2-CONH-CH2-CONH-CH2-CONH-CH2-COOH.

Key concepts

glycine

Glycine is the simplest form of an amino acid. It is classified as an α-amino acid because all its functional groups are attached to a central carbon, known as the α-carbon. Glycine's structure is unique due to its side chain. Unlike other amino acids that possess more complex side chains, glycine's side chain is merely a hydrogen atom (H).

Because of this simple configuration, glycine is highly versatile in the formation of various peptides and proteins. This also makes glycine relatively non-reactive compared to other amino acids, often found in protein structures with tight turns.

• It contains an amino group (-NH2)
• A carboxyl group (-COOH)
• A single hydrogen atom as its side chain

Understanding glycine's fundamental role in biology is essential because it's involved in numerous metabolic pathways. Glycine is also significant in the formation of heme, purines, and other necessary biomolecules.

peptide bond

The peptide bond is a covalent bond that connects amino acids together to form peptides and proteins. The process of forming a peptide bond involves a reaction between the amino group of one amino acid and the carboxyl group of another. This results in the release of a water molecule (H2O), showcasing a classic example of a condensation reaction.

Peptide bonds are crucial for constructing complex protein structures. Once two or more amino acids are linked through peptide bonds, they form a polypeptide chain. These chains fold into specific shapes to perform diverse biological functions. Some important characteristics of peptide bonds include:

• Forming strong covalent connections between amino acids
• Contributing to the protein’s overall stability
• Being resistant to conditions that might normally break bonds, such as heat or acidity

When observing protein synthesis, understanding peptide bonding is critical since it dictates how proteins are formed and modified within the cell.

amino acid

Amino acids are often referred to as the building blocks of life. They form the building materials for proteins, which are essential for all cellular functions. Each amino acid contains both an amino group (-NH2) and a carboxyl group (-COOH).

The diversity within amino acids arises mainly from their side chains. Each side chain is distinct, leading to different properties, such as charge, polarity, and reactivity. These variations in structure allow amino acids to create proteins with a vast range of functions and structures.

• 20 amino acids are encoded by the universal genetic code.
• They can be categorized based on the characteristics of their side chains: non-polar, polar, acidic, or basic.
• The conjugation of amino acids through peptide bonds leads to the creation of proteins.

An understanding of amino acids and their structures is a critical foundation in biochemistry and molecular biology, given their pivotal roles in metabolism, energy production, and other biological processes.

condensation reaction

A condensation reaction is a chemical process where two molecules combine to form a larger molecule, while simultaneously releasing a small molecule such as water. This type of reaction is integral to biological systems, especially in synthesizing polymers from monomers.

In the context of peptide bond formation, the condensation reaction involves the interaction between the amino group of one amino acid and the carboxyl group of another. This reaction is central to forming the peptide bonds that link amino acids into polypeptide chains.

• Involves the removal of a small molecule (typically water).
• Essential for polymer formation, including proteins and carbohydrates.
• It is a critical step in many biosynthetic pathways within cells.

By comprehending the mechanism and implications of condensation reactions, one can appreciate how complex macromolecules like proteins are constructed and how these processes are vital for life.