During fasting, adipose tissue releases large amounts of glycerol from triglyceride lipolysis, yet this glycerol cannot be reutilised within the adipocyte itself for triglyceride resynthesis. The reason is:

• A Adipose tissue lacks hormone-sensitive lipase for glycerol phosphorylation
• B Adipose tissue lacks glycerol kinase, so free glycerol must travel to the liver for phosphorylation ✓
• C Free glycerol is rapidly oxidised by adipocyte glycerol-3-phosphate dehydrogenase
• D Glycerol is transported exclusively bound to albumin, inaccessible to adipocytes

Explanation

Reutilisation of glycerol requires its phosphorylation to glycerol-3-phosphate by glycerol kinase, an enzyme present in liver and kidney but absent from adipose tissue. Adipocytes therefore generate glycerol-3-phosphate for esterification from dihydroxyacetone phosphate via glycerol-3-phosphate dehydrogenase instead. Free glycerol released during fasting reaches the liver, where glycerol kinase converts it into a gluconeogenic substrate. Hormone-sensitive lipase cleaves triglyceride rather than phosphorylating glycerol.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.