Question

In an amino acid, a carbon atom bound directly to the carbonyl carbon of the acid function is called the alpha carbon \((\alpha\) -carbon \() .\) Draw glycine, point out the \(\alpha\) -carbon, and then explain why all 20 amino acids used to build human proteins are called \(\alpha\) -amino acids. Then draw the simplest \(\beta\) -amino acid.

Short answer

Glycine, the simplest amino acid, has the structure \(NH_{2}-CH_{2}-COOH\). The alpha carbon (\(\alpha\)-carbon) is the central carbon atom bonded to the amino group, carboxyl group, and two hydrogen atoms. All 20 amino acids used in building human proteins are called \(\alpha\)-amino acids because their amino group is attached to the \(\alpha\)-carbon. The simplest \(\beta\)-amino acid, beta-alanine, has the structure \(H_{2}N-CH_{2}-CH_{2}-COOH\), with the amino group bonded to the second carbon atom in the chain.

Step-by-step solution

Understanding the structure of an amino acid

Amino acids are the building blocks of proteins and consist of a central carbon atom, also known as the alpha carbon, bonded to an amino group (-NH2), a carboxyl group (-COOH), and a distinctive side chain (R group).

Drawing glycine and identifying the alpha carbon

Glycine is the simplest amino acid and has the formula NH2-CH2-COOH. Its structure can be drawn as follows: \[H_{2}N-CH_{2}-COOH\] In this structure, the alpha carbon is represented by the central carbon atom (C) bonded to the amino group, the carboxyl group, and two hydrogen atoms.

Explaining why all 20 amino acids are considered alpha-amino acids

All 20 amino acids used in building human proteins are referred to as alpha-amino acids because their amino group is attached to the alpha carbon, which is the carbon next to the carboxyl carbon. The alpha carbon is a key structural feature of amino acids and is crucial for forming peptide bonds that link amino acids together in proteins.

Drawing the simplest beta-amino acid

The simplest beta-amino acid, known as beta-alanine, has the amino group bonded on the carbon next to the alpha carbon. Its structure can be drawn as follows: \[H_{2}N-CH_{2}-CH_{2}-COOH\] In this structure, the beta carbon is represented by the second carbon atom (C) in the chain, bonded to the amino group, a hydrogen atom, and another carbon atom attached to the carboxyl group.

Key concepts

Amino Acid Structure

Amino acids are the fundamental building blocks of proteins. Each amino acid consists of a basic structure that involves a central carbon atom. This central atom is known as the alpha carbon. To this alpha carbon, several groups are attached: an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (H), and a distinctive side chain, often referred to as the R group. The R group varies among amino acids and is responsible for their diverse properties. The standard amino acid structure lays the foundation for forming most proteins in living organisms.

This structure provides amino acids with the ability to link together in specific sequences, forming proteins that serve numerous functions in the body. Understanding this structure is essential for appreciating how proteins perform their roles in biological systems.

• Central alpha carbon atom
• Amino group (-NH2)
• Carboxyl group (-COOH)
• Distinctive R group or side chain

Peptide Bonds

Peptide bonds are vital for linking amino acids to form proteins. These covalent bonds occur between the amino group of one amino acid and the carboxyl group of another, releasing a molecule of water in the process. This reaction is known as a condensation or dehydration synthesis reaction. Through a series of peptide bonds, amino acids form chains, which then fold into specific structures to become functional proteins. The sequence and number of amino acids, bonded through peptide bonds, determine the protein's final shape and function.

Once formed, these bonds provide structural integrity and flexibility to the protein chain, allowing it to become the complex forms necessary for biological activity.

• Formation between amino and carboxyl groups
• Condensation reaction (water released)
• Creates polypeptide chains
• Determines protein structure and function

Alpha Carbon

The alpha carbon (\(\alpha\)-carbon) is a notable feature in amino acids, providing a unique point of linkage for essential functional groups. This carbon atom acts as the anchor point for both the amino group and the carboxyl group. It plays a crucial role in the versatility of amino acids and their capacity to join into peptide bonds, making it indispensable in protein assembly.

The positioning of the alpha carbon relative to other groups ensures that the amino acid can participate efficiently in forming necessary biochemical structures like enzymes, channels, and receptors. All protein-forming amino acids have their amino group attached to this alpha carbon, which is why they are often referred to as alpha-amino acids. This consistent feature across amino acids allows them to interact and form stable, functional proteins.

• Central point of connection for groups
• Facilitates peptide bond formation
• Key in forming biochemical structures

Beta Amino Acids

While alpha-amino acids are common in proteins, beta-amino acids offer an intriguing variation. In beta-amino acids, such as beta-alanine, the amino group is connected to the beta carbon instead of the alpha carbon. The beta carbon is the second carbon atom from the carboxyl group. This different structure introduces unique properties and functionalities compared to alpha-amino acids.

Beta-amino acids are less common in proteins, but they still find specific applications in pharmaceuticals and synthetic processes. By studying beta-amino acids, scientists explore possibilities in creating new compounds with potential benefits. Beta-amino acids illustrate the diversity of amino acid structures beyond the typical protein-building blocks.

• Amino group attached to beta carbon
• Second carbon from carboxyl group
• Unique properties and uses