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58 Cards in this Set
- Front
- Back
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The pentose-phosphate pathway and the conversion to sorbitol are 2 metabolic fates of the molecule ___________
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glucose
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Glycogen stores much (more, less) energy than lipids in the human body
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less
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Glycogen is important in that it provides energy to cells that rely exclusively on ___________
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glucose
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The brain uses glucose as a main energy source because
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fatty acids cannot pass the blood brain barrier
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Red blood cells use glucose as a main energy source because
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they dont have mitochondria
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Kidney medulla, lens of the eye and testes use glucose as a main energy source because
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they are poor in mitochondria
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Exercising muscle utilizes glycogen stores because
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it quickly requires energy in the form of glucose
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Gluconeogenesis occurs in the
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liver and kidney cortex
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In short term fasting, blood glucose levels are maintained by
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liver glycogen degradation
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In long term fasting, blood glucose levels are maintained by
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gluconeogenesis by the liver (and some extent by kidney)
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Does muscle glycogen provide glucose to the bloodstream? Why or why not?
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No. The enzyme that converts glucose-6-P to glucose is not expressed in muscle
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T or F. Glycogen is used for energy production in most tissues.
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True. Except for the liver
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What is the function of glycogen in the liver?
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RAISING BLOOD GLUCOSE LEVELS. Glycogen does not produce energy in the liver as it does in other tissues. Instead, the liver contains the enzyme that converts glucose 6-phosphate (the form of glucose that can be used by cells) into plain ol' glucose, which exits the cell and goes into the blood stream
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When glycogen degradation is activated, what happens to glycolysis?
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Glycolysis is inhibited so that blood glucose levels can increase to a functional level
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In utero, the embryo gets its blood glucose from the mother. How does a baby maintain blood glucose levels once born?
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In the last 10 weeks of pregnancy, baby builds glycogen stores due to increased insulin levels. After birth, the baby degrades glycogen due to glucagon and epinepherine.
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If a mother is malnourished during the last 10 weeks of pregnancy, the baby will
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become severely hypoglycemic because he was unable to build sufficient glycogen stores using the mother's glucose
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Where in the cell is glycogen located?
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cytoplasm
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What structure binds glucose covalently in glycogen?
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glycogenins through a tyrosine residue
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Glycogen has _______ linkages between adjacent residues and __________ between branched residues. Branches occur at every _______ glucose residue.
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-alpha-1,4-glycosidic
-alpha-1,6-glycosidic -8 to 10th |
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What enzyme in the liver converts glucose 6-phosphate to glucose? Where is it only found?
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glucose-6-phosphatase
found only in liver |
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Synthesis and degradation of glycogen (are, are not) reversible processes.
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ARE NOT
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UDP glucose is the ______________ form of glucose
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nucleotide-activated
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Glucose needs to be nucleotide activated (into UDP-glucose) for what reason?
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in order to build oligo or polysaccharides
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UDP-glucose is formed by what enzyme?
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UDP-glucose-pyrophosphorylase
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Glycogen chain elongation is catalyzed by what enzyme?
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glycogen synthase
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In the lysosome, acid alpha-glucosidase is the enzyme through which
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glycogen is degraded (minor route)
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In the cytoplasm, the major route through which glycogen is degraded is through the enzyme
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glycogen phosphorylase
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Is glycogen phosphorylase in the brain, skeletal muscle, and liver all the same?
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NO. Different isoforms
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In Von Gierke disease, there is a deficiency in the enzyme ________________
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glucose 6-phosphatase. this makes it so the liver and kidney cannot convert glucose 6-P to glucose
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Glucose 1-P is converted to glucose 6-p by the enzyme
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phosphoglucomutase
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Glucose 6-P is transferred from the cytosol to the ER (where it can be converted to glucose) by what enzyme?
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glucose 6-P translocase
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Where in the cell does glucose 6-phosphate get converted to glucose?
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in the ER
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How is newly converted glucose transported out of the ER into the cytosol?
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transporter GLUT-7
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How does glucose get transferred out of the cytosol of liver cells and into blood circulation?
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transporter GLUT-2
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deficient in glucose 6 phosphatase...what disease?
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type Ia glycogen storage disease Von Gierke
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deficient in glucose 6-phosphatase translocase...what disease?
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type 1b glycogen storage disease
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deficient in lysosomal acid alpha-glucosidase...what disease?
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type II glycogen storage disease "Pompe"
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deficient in debranching enzyme...what disease?
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type IIIa: liver and muscle
type IIIb: liver only |
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deficient in glycogen phosphorylase in skeletal muscle..what disease?
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Type V "McArdle"
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deficient in glycogen phosphorylase in liver...what disease?
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Type VI glycogen storage disease (Hers)
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Von Gierke, in addition to decreasing glucose released from the cell, impairs _________________.
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gluconeogenesis
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T or F. Glucagon affects both muscle and liver.
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F. Only liver. Therefore, fasting, although it causes glucagon to be released, only affects the liver and has no effect on muscle glycogen stores
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Glycogen degradation is activated by ______________ of glycogen phosphorylase.
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phosphorylation
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Glycogen synthesis is inhibited by _______________ of glycogen synthase
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phosphorylation
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Glucagon pathway steps?
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1. glucagon acts thru G-protein linked receptor to activate adenylyl cyclase and PROTEIN KINASE A
2. Protein kinase A phosphorylates PHOSPHORYLASE KINASE (active) and glycogen synthase (inactive). 3. Phosphorylase kinase phosphorylates GLYCOGEN PHOSPHORYLASE (active). 4. Glycogen is DEGRADED. |
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Epinepherine, the fight or flight, hormone, degrades _____________.
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glycogen to make glucose for immediate energy use
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Epinepherine acts through what 2 receptors?
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alpha 1 adrenergic receptor - g-linked protein pathway w/secondary messengers that activates PHOSPHOLIPASE C-beta
beta 1 adrenergic receptor - same as glucagon pathway |
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In the phospholipase C-beta pathway, _______________ activates calmodulin dependent protein kinase and phosphorylase kinase. These enzymes inactivate glycogen synthase and activate glycogen phosphorylase (degradation).
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Ca2+ calmodulin
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Insulin uses a ____________ receptor.
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tyrosine kinase
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Insulin activates protein phosphatases. Protein phosphatases ____________
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dephosphorylate
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Insulin dephosphorylates glycogen phosphorylase, making it (Active/inactive) and glycogen synthase, making it (active/inactive)
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-inactive
-active |
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Insulin favors glycogen synthesis or degradation?
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synthesis
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Insulin activates ______________, which destroys cAMP.
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phosphodiesterase
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Exercise stimulates the release of ___, which induces glycogen degradation through the formation of ________.
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-Ca2+
-Ca2+ calmodulin |
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Under short term fasting, the main source of glucose is from
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liver glycogen. Muscle glycogen cannot provide glucose for circulation
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increased lactic acid
increased uric acid increased lipids decreased fasting glucose growth retardation delayed puberty these are all symptoms of what disease? |
type 1 glycogen storage disease, deficiency in either glucose 6 phosphatase or translocase
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cardiomegaly
normal blood glucose weak muscle tone these are all symptoms of what disease? |
type 2 glycogen storage disease
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cramping muscle after exercise
increased myoglobin no increase in lactate after exercise weakness after exercise these are all symptoms of what disease? |
type V glycogen storage disease (McArdle)
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