Question

Which of these statements concerning peptide bonds is FALSE? (A) Their formation involves a reaction between an amino group and a carboxyl group. (B) \(\quad\) They are the primary bonds that hold amino acids together. (C) \(\quad\) They have partial double bond character. (D) Their formation involves hydration reactions.

Short answer

Option D is false.

Step-by-step solution

- Identify the Nature of Peptide Bonds

Peptide bonds are covalent chemical bonds formed between two amino acid molecules. Specifically, they form when the carboxyl group of one amino acid reacts with the amino group of another, releasing a water molecule.

- Verify Option A

Option A states that peptide bond formation involves a reaction between an amino group and a carboxyl group. This is true because the carboxyl group of one amino acid reacts with the amino group of another.

- Verify Option B

Option B states that peptide bonds are the primary bonds that hold amino acids together. This is correct, as peptide bonds are the main linkages in protein structures.

- Verify Option C

Option C states that peptide bonds have partial double bond character. This is also true due to resonance in the amide linkage, leading to a partial double bond structure.

- Verify Option D

Option D states that peptide bond formation involves hydration reactions. This is false. Peptide bond formation is a dehydration synthesis reaction, not a hydration reaction. A water molecule is released during the process.

- Conclusion

After analyzing all options, it is clear that the FALSE statement is Option D.

Key concepts

Amino Acids

Amino acids are the building blocks of proteins. Each amino acid has a basic structure that includes a central carbon (C) atom, a hydrogen (H) atom, an amino group (-NH₂), a carboxyl group (-COOH), and a variable R group or side chain.
The R group differentiates one amino acid from another and determines the characteristics of the amino acid, such as whether it is hydrophilic (water-loving) or hydrophobic (water-fearing).
There are 20 common amino acids found in proteins, each with a unique R group.

Dehydration Synthesis

Dehydration synthesis, also known as a condensation reaction, is a chemical process by which two molecules are joined together to form a larger molecule, along with the release of a water molecule.
In the context of peptide bond formation, dehydration synthesis occurs when the carboxyl group (-COOH) of one amino acid reacts with the amino group (-NH₂) of another amino acid.
During this reaction, a molecule of water (H₂O) is released as the carboxyl group loses a hydroxyl group (-OH) and the amino group loses a hydrogen atom (H).
This linkage results in the formation of a peptide bond, which is a key feature in the structure of proteins.
Dehydration synthesis is crucial for the formation of complex molecules like proteins, carbohydrates, and nucleic acids.

Protein Structures

Proteins are complex molecules made up of one or more chains of amino acids linked by peptide bonds. The structure of a protein can be described at several levels:

• Primary structure: This is the linear sequence of amino acids in the polypeptide chain. The order of amino acids is determined by the genetic code and is crucial for the protein's function.


• Secondary structure: This involves the local folding of the polypeptide chain into structures such as alpha-helices and beta-sheets. These structures are stabilized by hydrogen bonds between the backbone atoms of the amino acids.


• Tertiary structure: This is the overall 3D shape of a single polypeptide chain, formed by interactions between the side chains (R groups) of the amino acids. These interactions include hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges.


• Quaternary structure: Some proteins are made up of more than one polypeptide chain. The quaternary structure describes the way these multiple chains are arranged and interact to form the final functional protein.

Understanding these levels of structure is essential for grasping how proteins function and how they interact with other molecules in the body.