True statement regarding insulin:: (A) Produced by alpha cells of pancreas, (B) Two polypeptide chains are bound by disulfide linkages, (C) Shifts potassium outside the cell, (D) S.c insulin tl/2 is 60 mins
Answer is B. Ref: Harper's Illustrated Biochemistry,28th editionExplanation:InsulinSecreted from pancreatic islet b cellsReleased regulated by blood (glycemic thresholdSynthesized as a single chain : pro-insulinInsulin is formed from proinsulin (removal of the connecting or "C" peptide)Insulin is thus made up of 2 chainsA (21 amino acids) and B (30 amino acids)Connected to each other by 2 inter disulfide bridges and 1 intra disulfide bridgeAll necessary for its hormone activity.ActionsStimulates glucose oxidation & storage and inhibits glucose productionStimulates glycogen synthaseInhibits phosph orylaseInhibits gluconeogenesisStimulates glucose transport into adipocytes, which is then converted intoTGInhibits hormone-sensitive lipase (HPL) (|cAMP) and lipoprotein lipaseActivates GLUT1Stimulates fatty acid and triglyceride synthesisInhibits I i poly sis and proteolysisShifts potassium ions from ECF to ICF