Chapter 2 - Section 2.4 - Study Guide - Assess Your Learning Outcomes - Page 74: 11

Amino acids are polymerized to form proteins through a process called **condensation** or **dehydration synthesis**. During this process, amino acids are joined together, and a molecule of water is removed. Here's how it works: 1. **Amino Acid Structure:** Amino acids have a central carbon atom (the α-carbon) bonded to four groups: an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (-H), and an R-group (side chain). The R-group varies among different amino acids. 2. **Peptide Bond Formation:** - Two amino acids are brought close together so that the carboxyl group of one amino acid and the amino group of the other amino acid are adjacent. - The carboxyl group (-COOH) of one amino acid reacts with the amino group (-NH2) of the other amino acid. - In this reaction, a condensation or dehydration synthesis occurs, leading to the removal of a molecule of water (H2O). - The carbon from the carboxyl group and the nitrogen from the amino group bond together, forming a covalent bond called a **peptide bond**. - The resulting structure is a dipeptide, which consists of two amino acids linked by a peptide bond. 3. **Polymerization:** This process can continue as additional amino acids are added one by one, extending the peptide chain. The resulting chain of amino acids, linked by peptide bonds, is called a **polypeptide**. 4. **Protein Formation:** A protein is a functional molecule composed of one or more polypeptide chains that have folded into a specific three-dimensional structure. The unique sequence of amino acids in the polypeptide chain, known as the primary structure, determines the protein's structure and function. **Structure of a Peptide Bond:** A peptide bond is a type of covalent bond formed between the carbon atom (C=O) of the carboxyl group of one amino acid and the nitrogen atom (N-H) of the amino group of another amino acid. This bond has some distinctive structural characteristics: - It is a **planar** (flat) bond due to partial double-bond character, resulting from resonance between the oxygen and nitrogen atoms. - The bond involves the sharing of electrons between the carbon and nitrogen atoms. - The atoms within a peptide bond are nearly in the same plane, and the bond itself has partial double-bond character due to the resonance between the oxygen and nitrogen atoms. This restricted rotation around the peptide bond plays a crucial role in determining protein structure. In summary, amino acids are polymerized to form proteins through condensation reactions, with the formation of peptide bonds between the carboxyl group of one amino acid and the amino group of another. These peptide bonds give rise to the linear sequence of amino acids in a polypeptide chain, which ultimately folds into the three-dimensional structure of a functional protein.

Amino acids are polymerized to form proteins through a process called **condensation** or **dehydration synthesis**. During this process, amino acids are joined together, and a molecule of water is removed. Here's how it works: 1. **Amino Acid Structure:** Amino acids have a central carbon atom (the α-carbon) bonded to four groups: an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (-H), and an R-group (side chain). The R-group varies among different amino acids. 2. **Peptide Bond Formation:** - Two amino acids are brought close together so that the carboxyl group of one amino acid and the amino group of the other amino acid are adjacent. - The carboxyl group (-COOH) of one amino acid reacts with the amino group (-NH2) of the other amino acid. - In this reaction, a condensation or dehydration synthesis occurs, leading to the removal of a molecule of water (H2O). - The carbon from the carboxyl group and the nitrogen from the amino group bond together, forming a covalent bond called a **peptide bond**. - The resulting structure is a dipeptide, which consists of two amino acids linked by a peptide bond. 3. **Polymerization:** This process can continue as additional amino acids are added one by one, extending the peptide chain. The resulting chain of amino acids, linked by peptide bonds, is called a **polypeptide**. 4. **Protein Formation:** A protein is a functional molecule composed of one or more polypeptide chains that have folded into a specific three-dimensional structure. The unique sequence of amino acids in the polypeptide chain, known as the primary structure, determines the protein's structure and function. **Structure of a Peptide Bond:** A peptide bond is a type of covalent bond formed between the carbon atom (C=O) of the carboxyl group of one amino acid and the nitrogen atom (N-H) of the amino group of another amino acid. This bond has some distinctive structural characteristics: - It is a **planar** (flat) bond due to partial double-bond character, resulting from resonance between the oxygen and nitrogen atoms. - The bond involves the sharing of electrons between the carbon and nitrogen atoms. - The atoms within a peptide bond are nearly in the same plane, and the bond itself has partial double-bond character due to the resonance between the oxygen and nitrogen atoms. This restricted rotation around the peptide bond plays a crucial role in determining protein structure. In summary, amino acids are polymerized to form proteins through condensation reactions, with the formation of peptide bonds between the carboxyl group of one amino acid and the amino group of another. These peptide bonds give rise to the linear sequence of amino acids in a polypeptide chain, which ultimately folds into the three-dimensional structure of a functional protein.