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35 Cards in this Set
- Front
- Back
What are the tissues cells that primarily use glucose for energy?
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Brain: fatty acids cannot pass the blood-brain barrier
RBC's: don't have mitochondria Kidney medulla, lens, cornea of eye, testes: poor in mitochondria exercising muscle: short term high intensity exercise requires glucose (blood glucose levels have to be maintained to supply substrate for tissues that primarily rely on glucose as an energy source!) |
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What are the 3 main sources of glucose in the human body?
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-diet
-glycogen -gluconeogenesis |
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How are blood glucose levels maintained in the human body during fasting?
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SHORT TERM FASTING: maintained by degradation of liver glycogen (24 hours)
LONG TERM FASTING: maintained through gluconeogenesis by liver |
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What is the structure of glycogen?
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-glucose polymer
-branched structure -branches occur at every 8-10th glucose molecule |
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How is liver and muscle glycogen utilized?
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Liver: maintenance of blood glucose levels during short term fasting
Muscle: provide energy to exercising muscle (muscle doesn't release glucose into circulation) |
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What are the basic steps of glycogen synthesis?
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-glucose has to be converted to UDP-glucose to build glycogen
-initiation and elongation of glycogen chains (glycogenin, chains elongated by glycogen synthase) -branch formation in glycogen (catalyzed by branching enzyme) |
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What are the basic steps of glycogen degradation?
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GLYCOGENOLYSIS
-chain shortening (glycogen phosphorylase degrades it, glucose removed as glucose 1-P) -removal of branches (debranching enzyme, it removes free glucose) |
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Recognize metabolic diseases of glycogen degradation by associating with enzyme deficiencies and accumulated metabolites basic symptoms
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look at table on slides
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What are the allosteric regulators of glycogen metabolism?
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In the LIVER:
-glucose will (-) degrade glycogen metabolim MUSCLE: -when there is Ca and AMP in muscle, it would run the reaction because it needs energy In both LIVER and MUSCLE -Glucose 6-P will synthesize and degrades it |
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What are the hormones that regulate glycogen metabolism in the liver and muscle?
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LIVER: glucagon (fasting), insulin (well-fed), epinephrine
MUSCLE: epinephrine, inculin (glucagon does not affect muscle glycogen metabolism because fasting has little effect on muscle glycogen stores) |
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How are the enzymes of glycogen metabolism regulated by phosphorylation/dephosphorylation?
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Glycogen <----> Glucose 1-phosphate
Insulin will dephosphorylate the reaction to make glycogen by activating protein phosphatase Glucagon (cAMP) will phosphorylate it to make glucose 1-phosphate by activating phosphorylase kinase. |
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What is the role of gluconeogenesis in the liver and kidney cortex?
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LIVER:
-it is responsible for maintaining blood glucose levels for the entire body KIDNEY CORTEX: -mainly provides glucose for kidney medulla but some glucose also gets into the systemic circulation |
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What is the major gluconeogenic substrates?
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Lactate
glycerol (from triglycerides in adipose tissue) glucogenic amino acids (alanine is the main one) |
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Explain the glucose/alanine and Cori cycles in gluconeogenesis.
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GLUCOSE/ALANINE cycle
-glucose goes into the muscle from the bloodstream, then it runs through glycolysis making pyruvate. ]-pyruvate ---> alanine through transamination -Alanine is then transported to the kiver ---> pyruvate, and through gluconeogenesis makes glucose again -this glucose can then be used by muscles again and the cycle can continue (mainly muscle and intestine) CORI Cycles (exercising muscle, RBCs and WBCs) -pretty much same as G/A cycle but lactate is formed and goes into the blood to the liver. -from there lactate goes through gluconeogenesis to for glucose |
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List the steps of gluconeogenesis, which are not the reverse reactions of glycolysis.
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CONVERSION OF PYRUVATE TO PHOSPHOENOLPYRUVATE (3rd irrevers. step of glycolysis)
-pyruvate ---> oxaloacetate -oxal. cannot cross mitochondrial membrane so it is converted to malate -malate can then ---> oxaloactate in cytosol ---> PEP DEPHOSPHORYLATION OF FRUCTOSE 1, 6-BISPHOSPHATE -F 1, 6-bis is dephosphorylated by fructose 1, 6-bisphosphatase (regulatory steps of gluconeogenesis) -opposite of PFK-1 regulation (PFK-2 becomes inactive, decreased inhibition of FBP-1, increasing rate of gluconeogenesis) DEPHOSPHORYLATION OF GLUCOSE 6-PHOSPHATE -glucose 6-phosphate --> glucose (using glucose 6-phosphatase--dephosphorylates) |
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Calculate the ATP needed for producing a certain amount of glucose.
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For each synthesis of glucose molecules, gluconeogenesis requires 6 ATP molecules (4 ATP + 2 GTP)
-needs that many because there are 2 pyruvates (3 carbon) that are formed from the 1 glucose (6 carbon) |
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Explain the regulation of gluconeogenesis and compare it to the regulation of glycolysis.
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Basically it works opposite of one another.
-at low glucose levels, the glucokinase is not active so glycolysis is inhibited and gluconeogenesis runs because you need more in the bloodstream |
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What is Von Gierke Disease (type 1)?
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deficient enzyme: glucose 6-phosphatase
organs involved: hepatomegaly (fatty liver), renomegaly blood metabolites: - increased lactic acid, uric acid lipids - decreased glucose during fasting (growth retardation, delayed puberty) |
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Pompe Disease (type 2)
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Enzyme: alpha (1-4)-glucosidase (lysosomal)
Organs: cardiomegaly Blood metabolites: normal blood glucose (general weak muscle tone) |
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McArdle Syndrome (type 5)
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Enzyme: glycogen phosphorylase (skeletal muscle)
Organs: cramping of skeletal muscle after exercise Blood metabolites: increased myoglobin (muscles are broken down), no increase in lactate after exercise Urine metabolites: increased myoglobin (temporary weakness after exercise) |
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What are the main functions of glycogen in the liver and muscle?
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Liver: maintenance of BLOOD GLUCOSE levels during short term fasting (gluconeogenesis by liver for long term fasting)
Muscle: provides energy to exercising muscles |
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What is needed in order to build complex carbohydrates from monosaccharides?
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The building blocks must be nucleotide activated!
-glucose needs to be converted to UDP-glucose to build glycogen |
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What is transaldolase?
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transfers 3 carbon units
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transketolase?
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transfers 2 carbon units
-requires thiamine pyrophosphate (vit B1) as a cofactor patients' vitamin B1 (thiamine) levels are measured by the activity of red blood cell transketolase |
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What is NADPH's role in nitric oxide production?
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-vasodilator: relaxes vascular smooth muscle cells
-anticoagulant: inhibits platelet aggregation -neurotransmitter: in brain -antibactericidal: reats with superoxide and forms highly reactive radicals that kill pathogens |
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WHAT is NADPH's role in phagocytosis?
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-NADPH oxidase generates superoxide that destroys bacteria (needs NADPH)
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What is Chronic granulomatous disease?
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-NADPH oxidase is deficient
-can't kill off bacteria because superoxides cannot destroy bacteria -nodular areas that sequester bacteria |
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What is glutathione?
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-tripeptide
-detoxifies H2O2 by glutathione peroxidase -in the process, glutathione gets oxidized -glutathione (oxidized) has to be reduced (by glutathione reductase) to be able to neutralize another H2O2 molecule -glutathione reductase requires NADPH to reduce glutathione (process is primary defense mechanism of red blood cells against oxidative damage) |
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What happens when there is a glucose 6-phosphate dehydrogenase deficiency?
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-acute hemolytic anemia
(increased oxidative stress because NADPH cannot be made to remove the H2O2) -fatgue, pallor, shortness of breath -high bilirubin levels (increased degradation of hemoglobin--hemolysis, more oxidative stress) -high reticulocyte count (more immature RBC's produced by bone marrow) G6PD deficiency confers resistance to malaria infections |
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What is lactose made of?
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galactose and glucose
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Classic Galactosemia
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uridyltransferase deficiency
-causes galactosemia, galctosuria, vomiting, diarrhea, jaundice -accumulation of galactose 1-phosphate and galactitol in nerve, lens, liver, and kidney tissues -causes liver damage, severe mental retardation, and cataracts -THERAPY: removal of galactose (and therefore lactose) from diet |
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Lactose synthesis
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2 proteins catalyze lactose synthesis
-UDP-galactose + glucose-->lactose + UDP |
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What is fructose made of?
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sucrose and glucose
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Aldolase A and Aldolase B
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Aldolase A in glycolysis can make dihydroxyacetone P and glyceraldehyde 3-P--->pyruvate for energy production
Aldolase B (during 2nd step of fructose metabolism) helps make glyceraldehyde--> phosphoglyceride synthesis/triacylglycerol synthesis) and dihydroxyacetone-P (same as aldolase A to go down glycolysis or gluconeogenesis) |
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disorder of fructose metabolism
-hereditary fructose intolerance (fructose poisoning) |
absence of aldolase B: leads to intracellular trapping of fructose 1-P and LOW ATP
-causes severe hypoglycemia, vomiting, jaundice, hemorrhage, hepatomegaly -therapy: removal of fructose and sucrose from diet |