Biology · Biomolecules · NEET
A peptide bond. It forms between the -COOH group (carboxyl) of one amino acid and the -NH2 group (amino) of the next amino acid, with loss of one water molecule (dehydration). So proteins are chains of amino acids joined by peptide bonds. This is why proteins are called polypeptides.
A glycosidic bond joins sugar (monosaccharide) units in carbohydrates like starch, cellulose, and inulin. A peptide bond joins amino acids in proteins. Simple trick: sugar to sugar = glycosidic; amino acid to amino acid = peptide. NEET often pairs these two, for example inulin (glycosidic) and insulin (peptide).
A phosphodiester bond. It joins the sugar of one nucleotide to the phosphate, and that phosphate to the sugar of the next nucleotide. This creates the sugar-phosphate backbone of the DNA and RNA chain. The word 'di-ester' means the phosphate forms two ester links, one on each side.
An ester bond. It forms between the -COOH group of a fatty acid and the -OH group of glycerol. A triglyceride has three fatty acids joined to one glycerol by three ester bonds. The enzyme lipase breaks these ester bonds, which is a common NEET match.
Match by the biomolecule the enzyme acts on. Protease breaks peptide bonds (protein). Amylase breaks glycosidic bonds (starch). Lipase breaks ester bonds (lipid). Nuclease breaks phosphodiester bonds (nucleic acid). This exact set was asked in NEET 2024.
Match List I with List II: List I: A. Lipase; B. Nuclease; C. Protease; D. Amylase. List II: I. Peptide bond; II. Ester bond; III. Glycosidic bond; IV. Phosphodiester bond.
Identify the substances having glycosidic bond and peptide bond, respectively, in their structure:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Yes. A peptide bond is a strong covalent bond formed between the carboxyl group of one amino acid and the amino group of the next, with removal of water. All four bond types here (peptide, glycosidic, ester, phosphodiester) are covalent bonds.
Because one phosphate group forms two ester linkages, one to the sugar of the nucleotide before it and one to the sugar of the nucleotide after it. 'Di' means two and 'ester' means the phosphate-sugar link. This bond builds the sugar-phosphate backbone of DNA and RNA.
Yes. Peptide, glycosidic, ester, and phosphodiester bonds all form by dehydration (condensation), where one water molecule is removed as the two units join. They are broken by hydrolysis, where water is added back, which is what digestive enzymes do.
A phosphoester (ester) bond links the phosphate to the sugar within one nucleotide. When nucleotides join into a chain, a phosphodiester bond connects them. For NEET, remember the chain-joining bond in DNA/RNA is the phosphodiester bond.
