Which of the following statements about peptide bonds are true? 1) a tetrapeptide contains five amino acid residues. 2) peptide bonds form from nucleophilic attack by an electron pair on an alpha - amino nitrogen atom on an alpha - carboxyl carbon atom of another amino acid. 3) peptide bonds are ester linkages. 4) peptides are polymers of amino acids. 5) peptide bond formation is a hydrolysis reaction

The correct answers are:

2) Peptide bonds form from nucleophilic attack by an electron pair on an alpha - amino nitrogen atom on an alpha - carboxyl carbon atom of another amino acid and

4) Peptides are polymers of amino acids.

A peptide bond is an amide type of covalent chemical bond. It is formed between two amino acids:  C1 (carbon end) of one alpha-amino acid and N2 (nitrogen end) of another. Peptide bonds are the basis for the formation of a peptide chain and consequently protein.  Formation of peptide bond is a condensation process, meaning that when two amino acids combine and link, water molecule is released and dipeptide is a product of that reaction.

The statement that is true about peptide bonds is;

"Peptide bonds form from nucleophilic attack by an electron pair on an alpha-amino nitrogen atom on an alpha-carboxyl carbon atom of another amino acid."

Further Explanation:  Amino acids  Amino acids act as a building blocks of proteins. They are made up of an amide group (NH2) and a carboxyl group (COOH). There are 21 amino acids present in proteins and are classified as either essential or non-essential. Essential amino acids are those that are obtained from the diet as humans can not synthesis them. Non-essential amino acids on the other hand are those that can be synthesized in the body. Proteins  Proteins are among the four macro-molecules in living organisms others being; lipids, carbohydrates, and nucleic acids. Many amino acids join together through peptide bonds to form polypeptide chains that join to form proteins. Peptide bonds  Peptide bonds are type of amide linkages that join amino acids together to form polypeptides or proteins. Each amino acid in a protein is joined to another by a peptide bond. During the formation of a peptide bond a carboxyl group of one amino acid combine with an amino group of another amino acid and a molecule of water is released.A nucleophilic attack by an electron pair on an alpha-amino nitrogen atom on an alpha-carboxyl carbon atom of another amino acid results to the formation of a peptide bond between two amino acid.Therefore, peptide bond formation is an example of a dehydration reaction due to the release of water molecules.

Keywords; Proteins, amino acids, peptide bonds  

Learn more about: Macromolecules: Proteins: Amino acids: Peptide bonds:

Level: High school  

Subject: Biology  

Topic: Macro-molecules  

Sub-topic: Peptide bonds and amino acids

I'm not sure if i fully understood your question but i'll go ahead and answer it .. The DNA molecule has the promotor region which is detected by the transcription factors that are responsible to start transcription ( and hence , unzipping the dna strands )