True statement regarding insulin:
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
Produced by alpha cells of pancreas
Two polypeptide chains are bound by disulfide linkages
Shifts potassium outside the cell
S.c insulin tl/2 is 60 mins
Chemistry of Carbohydrates, Amino sugars, and Mucopolysaccharides