Problem 55 - Chemistry: The Central Science

Question

(a) What is an \(\alpha\) -amino acid? (b) How do amino acids react to form proteins? (c) Draw the bond that links amino acids together in proteins. What is this called?

Step-by-Step Solution

Answer

(a) An α-amino acid is a molecule with an amino group (-NH2) and a carboxyl group (-COOH) bonded to the same α-carbon, which also has a hydrogen atom and a unique side chain (R group). (b) Amino acids react to form proteins through peptide bond formation, where the amino group of one amino acid reacts with the carboxyl group of another, creating a peptide bond and releasing a water molecule. (c) The bond linking amino acids in proteins is a peptide bond (\(-\)C(O)NH\(-\)), which is a covalent bond formed between the carbonyl carbon of one amino acid and the nitrogen atom of another amino acid, creating a polypeptide chain.

Step 1: (a) Definition of an α-amino acid

An α-amino acid is a molecule that contains both an amino group (-NH2) and a carboxyl group (-COOH) bonded to the same carbon atom, known as the α-carbon. The α-carbon is also bonded to a hydrogen atom and a side chain (R group), which is unique to each amino acid and determines its specific properties.

Step 2: (b) Protein formation

Amino acids react to form proteins through a process called peptide bond formation. During this process, the amino group of one amino acid reacts with the carboxyl group of another amino acid, releasing a water molecule (H2O) in a condensation reaction. This results in the formation of a peptide bond between the amino acids, linking them together into a chain called a polypeptide. The sequence of amino acids in the polypeptide chain determines the structure and function of the resulting protein.

Step 3: (c) Peptide bond and its name

The bond that links amino acids together in proteins is called a peptide bond (\(-\)C(O)NH\(-\)). A peptide bond is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another amino acid. The formation of a peptide bond results in a molecule where the carbonyl carbon of one amino acid is bonded to the nitrogen atom of the second amino acid. The chain of amino acids connected by peptide bonds is known as a polypeptide or protein.