Question

Name four compounds that contain anhydrous phosphate bonds. Name a compound that contains an anhydride bond that does not contain phosphorus, but is found in the TCA cycle?

      

What is the difference between an anhydrous bond and an ester bond? What is the biological significance of having a compound containing an anhydrous bond

Answer 1

Ans. A compound that can be derived by removing water molecule from another molecule is said to be an anhydride.

For example- sulfuric acid produces sulfur trioxide when a water molecule is produced from it. So, SO₃ is an anhydride.

                        H₂SO₄ -------> SO₃ + H₂O

# Acid anhydrides are characterized by presence of two acyl groups linked to the same O-atom.

# Four compounds with anhydrous phosphate bond – ATP, GTP, CTP, TTP, ADP, GDP, etc.

# An anhydride (a compound containing anhydride bond) lacking a phosphate group and NOT found in TCA cycle is – Acetic anhydride (CH₃CO)₂O

# Condensation of an organic acid and alcohol gives rise to ester. The ester bond has alkoxy group [ O-alkyl group ; or O-R ] in place of -OH of alcohol.

# Biological significance of anhydride bond: The hydrolysis of an anhydride bond is highly exergonic. So, these bonds, say hydrolysis of ATP, are hydrolyzed to produce energy required by the cell.

The anhydride bond is again synthesized (formation of ATP from ADP and Pi) by using the energy taken in form of food (ATP synthesis in mitochondria). ATP, the most significant form of cellular energy, is the most important anhydride from this perspective. It provide energy to the cell and convert into ADP and Pi. ATP is gain synthesized from ADP and Pi by using energy from food. The cycle goes on!