Klappa8.) Part 2 - Differences between liver and muscle cells concerning glycogen metabolism. Inherited defects of glycogen degradation (von Gierke’s disease, Mc Ardle syndrome).
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- FrontMain difference between liver and muscle glycogenBackLiver glycogen maintains blood glucose, whereas muscle glycogen provides ATP for muscle contraction
- FrontMain function of liver glycogenBackServes as a glucose reserve for the whole body and helps maintain blood glucose between meals and during early fasting
- FrontWhen liver glycogen is usedBackDuring fasting or low blood glucose to support the circulation
- FrontWhat the liver can do with glycogen-derived G6PBackConvert it to free glucose and release it into blood
- FrontVery high-yield summary of liver glycogenBackLiver glycogen maintains blood glucose
- FrontMain function of muscle glycogenBackServes as a local fuel store for ATP production during muscle contraction
- FrontHow muscle uses glycogen during contractionBackGlycogen is degraded to glucose-1-phosphate, then glucose-6-phosphate, which enters glycolysis
- FrontVery high-yield summary of muscle glycogenBackMuscle glycogen provides ATP for that muscle
- FrontSingle most important biochemical difference between liver and muscle glycogen metabolismBackLiver has glucose-6-phosphatase, whereas muscle does not
- FrontRole of glucose-6-phosphatase in liverBackConverts glucose-6-phosphate to free glucose
- FrontWhy liver can release glucose into bloodBackIt contains glucose-6-phosphatase
- FrontWhy muscle cannot release free glucose into bloodBackMuscle lacks glucose-6-phosphatase
- FrontWhat muscle does with glycogen-derived G6PBackKeeps it and uses it in glycolysis
- FrontHigh-yield sentence comparing liver and muscle glucose outputBackLiver can release glucose, whereas muscle cannot
- FrontHormonal triggers for glycogen breakdown in liverBackLow glycemia leading to glucagon release and adrenaline
- FrontMain triggers for glycogen breakdown in muscleBackEffort, high AMP, Ca2+ during contraction, and adrenaline
- FrontVery high-yield trigger comparisonBackGlucagon is for liver, whereas AMP and Ca2+ during contraction are especially important in muscle
- FrontEffect of glucagon on liver glycogenolysisBackActivates liver glycogen breakdown when blood glucose is low
- FrontWhy muscle glycogenolysis is not regulated like liver glycogenolysisBackMuscle responds mainly to its own energy state rather than directly to low blood glucose
- FrontHigh-yield glucagon comparisonBackLow blood glucose directly matters to liver glycogen, not to muscle glycogen in the same way
- FrontRole of AMP in muscle glycogen metabolismBackAMP is a major allosteric activator of glycogen phosphorylase in muscle
- FrontTissue specificity of AMP activation of glycogen phosphorylaseBackMuscle only
- FrontWhy AMP rises in contracting muscleBackATP is being consumed rapidly and adenylate kinase converts 2 ADP to ATP + AMP
- FrontWhy AMP activation of glycogenolysis makes sense in muscleBackLow ATP signals that muscle needs more fuel, so glycogen breakdown increases
- FrontHigh-yield AMP comparisonBackAMP activates muscle phosphorylase, not liver phosphorylase
- FrontShared allosteric inhibitors of glycogen phosphorylase in liver and muscleBackATP and glucose-6-phosphate
- FrontTissue-specific effect of free glucose on glycogen phosphorylaseBackOnly liver glycogen phosphorylase is inhibited by free glucose
- FrontEffect of glucose on muscle glycogen phosphorylaseBackIt does not allosterically inhibit muscle phosphorylase
- FrontHigh-yield glucose comparisonBackFree glucose inhibits liver glycogen phosphorylase, not muscle phosphorylase
- FrontRole of Ca2+ in glycogen metabolismBackActivates phosphorylase kinase through its calmodulin subunit
- FrontSpecial importance of Ca2+ in muscleBackIt is strongly linked to contraction
- FrontRole of Ca2+ in liver glycogen breakdownBackCan rise in response to epinephrine and help activate glycogen breakdown
- FrontHigh-yield Ca2+ comparisonBackCa2+ matters in both liver and muscle, but in muscle it is especially tied to contraction
- FrontFunctional end product of liver glycogen breakdownBackGlycogen is converted to G1P, then G6P, then free glucose that enters the blood
- FrontFunctional end product of muscle glycogen breakdownBackGlycogen is converted to G1P, then G6P, which enters glycolysis for local ATP production
- FrontPractical consequence of glucose-6-phosphatase differenceBackThe liver exports glucose to blood, whereas muscle uses glycogen-derived G6P locally in glycolysis
- FrontLiver glycogen summary table in wordsBackPurpose is blood glucose maintenance, it responds to glucagon and adrenaline, contains glucose-6-phosphatase, is inhibited by free glucose at phosphorylase, and can export glucose
- FrontMuscle glycogen summary table in wordsBackPurpose is ATP production for contraction, it responds to AMP, Ca2+, adrenaline, and exercise, lacks glucose-6-phosphatase, cannot export glucose, and sends glycogen-derived G6P into glycolysis
- FrontGeneral tissue pattern in glycogen storage diseasesBackGlycogen storage diseases often affect mainly liver or muscle
- FrontTypical hepatic symptoms in glycogen storage diseasesBackHepatomegaly and hypoglycemia appearing early
- FrontTypical muscle symptoms in glycogen storage diseasesBackWeakness, pain on effort, and myopathy appearing later
- FrontVon Gierke disease identityBackGlycogen storage disease type I
- FrontDeficient enzyme in von Gierke diseaseBackGlucose-6-phosphatase
- FrontWhy von Gierke disease occursBackIn liver, glycogenolysis and gluconeogenesis both produce G6P, but without glucose-6-phosphatase G6P cannot be converted to free glucose
- FrontWhy fasting hypoglycemia occurs in von Gierke diseaseBackThe liver cannot effectively release glucose during fasting
- FrontVery high-yield pathway effect in von Gierke diseaseBackIt affects both glycogen degradation and gluconeogenesis because both require the final G6P to glucose step
- FrontLecture findings in von Gierke diseaseBackAccumulation of glycogen in liver and renal tubule cells, hypoglycemia, lactic acidosis, ketoacidosis, and hyperlipemia
- FrontCore exam findings in von Gierke diseaseBackSevere fasting hypoglycemia, hepatomegaly with glycogen accumulation, lactic acidosis, hyperlipidemia, and often renal involvement
- FrontMechanism of lactic acidosis in von Gierke diseaseBackIf G6P cannot become glucose, it is diverted into glycolysis, increasing pyruvate and lactate production
- FrontKey clinical logic for von Gierke diseaseBackLiver disease with inability to release glucose causes severe fasting hypoglycemia
- FrontMcArdle syndrome identityBackGlycogen storage disease type V
- FrontDeficient enzyme in McArdle syndromeBackMuscle glycogen phosphorylase (myophosphorylase)
- FrontWhy McArdle syndrome occursBackMuscle glycogen cannot be broken down normally, so glycogen-derived G1P and G6P are not adequately available during exercise
- FrontEffect of McArdle syndrome on exercise glycolysisBackGlycolysis during exercise is impaired
- FrontMain metabolic consequence of McArdle syndrome during exerciseBackATP supply from muscle glycogen is limited, causing exercise intolerance
- FrontLecture findings in McArdle syndromeBackFatigue, high muscle glycogen content, and very low lactate in blood during exercise
- FrontCore exam findings in McArdle syndromeBackExercise intolerance or fatigue, muscle weakness or pain with exertion, increased muscle glycogen, and little or no rise in lactate during exercise
- FrontWhy lactate stays low in McArdle syndrome during exerciseBackMuscle glycogen phosphorylase deficiency prevents normal glycogen-derived substrate supply to glycolysis, so lactate does not rise appropriately
- FrontVon Gierke vs McArdle tissue comparisonBackVon Gierke mainly affects liver and kidney, whereas McArdle affects muscle
- FrontVon Gierke vs McArdle enzyme comparisonBackVon Gierke is due to glucose-6-phosphatase deficiency, whereas McArdle is due to muscle glycogen phosphorylase deficiency
- FrontVon Gierke vs McArdle main problem comparisonBackVon Gierke cannot release free glucose, whereas McArdle cannot break down muscle glycogen during exercise
- FrontVon Gierke hallmarkBackSevere fasting hypoglycemia
- FrontMcArdle hallmarkBackExercise intolerance with little or no rise in lactate during exercise
- FrontIntegrated logic for liver glycogen diseaseBackExpect hepatomegaly and hypoglycemia because liver is supposed to supply blood glucose
- FrontIntegrated logic for muscle glycogen diseaseBackExpect exercise weakness or pain and abnormal exercise lactate response because muscle glycogen is for local ATP generation
- FrontSuper high-yield liver vs muscle glycogen distinctionBackLiver glycogen maintains blood glucose, whereas muscle glycogen fuels contraction
- FrontSuper high-yield glucose-6-phosphatase distinctionBackLiver has glucose-6-phosphatase, whereas muscle does not
- FrontSuper high-yield glucagon factBackGlucagon activates liver glycogenolysis
- FrontSuper high-yield AMP factBackAMP activates glycogen phosphorylase in muscle only
- FrontSuper high-yield glucose inhibition factBackGlucose inhibits glycogen phosphorylase only in liver
- FrontSuper high-yield von Gierke factBackVon Gierke is glucose-6-phosphatase deficiency
- FrontSuper high-yield McArdle factBackMcArdle is muscle glycogen phosphorylase deficiency
- FrontSuper high-yield von Gierke consequenceBackVon Gierke causes severe fasting hypoglycemia
- FrontSuper high-yield McArdle consequenceBackMcArdle causes exercise intolerance and little or no rise in lactate during exercise
- FrontCheat-sheet liver vs muscle glycogenBackLiver keeps blood glucose up, muscle makes ATP for contraction, liver has glucose-6-phosphatase, muscle lacks glucose-6-phosphatase, glucagon acts on liver, AMP strongly activates muscle glycogenolysis, and glucose inhibits liver phosphorylase but not muscle phosphorylase
- FrontCheat-sheet von Gierke diseaseBackType I glycogen storage disease caused by glucose-6-phosphatase deficiency with liver and kidney glycogen accumulation, severe fasting hypoglycemia, lactic acidosis, and hyperlipidemia
- FrontCheat-sheet McArdle syndromeBackType V glycogen storage disease caused by muscle glycogen phosphorylase deficiency with exercise intolerance or fatigue, muscle glycogen accumulation, and very low or absent lactate rise during exercise
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