This is an extract of our Liver Control Of Blood Glucose document, which we sell as part of our Biochemistry Notes collection written by the top tier of Oxford students.
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Liver: regulation- maintainance of constant blood glucose concentration Sources of glucose in the blood
-Endogenous synthesis/ breakdown of endogenous stores Response to an increase in blood glucose after a meal
-Pancreas detects an increase in blood glucose concentrations - glucose enters through Glut2 transporters which transport glucose in proportion to the blood glucose concentrations- an increase in blood glucose absorbed into pancreatic beta cells- increases the ration of ATP/ADP and NADH/NAD+. This closes Katp channels which depolarises the cell- opens voltage gated calcium channels-depolarisationsecretion of insulin
-when insulin is released it acts on peripheral tissue which stimulates the uptake of glucose into cells. The amount of insulin released is proportional to the uptake of glucose
-liver: when there is an increase in blood glucose there is also a proportional increase in blood glucose transportation due to GLUT 2 transporters- increase in free glucose concentration acts as an allosteric inhibitor to glycogen phosphorylase and inhibits the break down of glycogen
-binding of insulin activates protein phosphatase and results in the complete inhibition of glycogen phosphorylase which results in the enzyme becoming unresponsive to allosteric inhibition. It also activates glycogen synthase
-excess substrates, amino acids, fructose and lactose are turned into glucose through gluconeogeneis and is stored as glycogen-this replenishes the endogenous stores. However the liver doesn't take up dietary glucose to store as glycogen directly Long period after meal: blood glucose concentration is LOW
-Glucagon is released by pancreas-activates protein kinase A- phosphorylates the glycogen phosphorylase kinase and glycogen phoshporylase-increased mobilisation of glycogen
-During excercise- adrenaline is released and also mobilises glycogen from the liver. After glycogen stores are depleted
-after glycogen stores are depleted gluconeogenesis occurs
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