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82 Cards in this Set
- Front
- Back
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What are isomers?
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Same formular, different structure
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What are Epimers?
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Isomers that differ around one carbon
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What are Enantiomers?
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Optical isomers.
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Are sugars usually D or L?
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D
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What are Anomers?
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Isomers that differ only in the orientation of one component in space.
Alpha - OH down Beta - Batter Up! OH Up. |
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What is mutarotation?
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The ring in a cyclic structure will open up and will interconvert between two structures.
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What is a reducing sugar?
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A sugar with a free O on the anomeric carbon, which reacts with copper and causes a colormetric reaction.
This reaction tells you that the carbon is free (reducing sugar) |
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What is a Glycosidic Linkage?
What are the important disaccharides? |
1,4 linkage via Oxygen
Lactose - Galactose and Glucose via a Beta 1,4 linkage Maltose - 2 Glucose monomers via an alpha 1,4 linkage, which is an orientation in which the O is below the linked rings and in between them. Sucrose - Glucose and Fructose via alpha 1,2 linkage |
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Is fructose a reducing sugar? Why or why not?
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No. There are no free anomeric carbons.
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What effect does branching have on solubility?
What is an example of a branched molecule? |
Positive effect on solubility
Ex: Amylose |
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Attached to nucleic Acid
With a phosphate group: |
Nucleoside
Nucleotide |
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What is billirubin?
What does accumulation cause? How can you get rid of it? |
The breakdown product of heme
Causes: The whites of the eyes to look yellow Get rid of it by adding sugars, making it more hydrophilic so that it cannot get into the cells |
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What enzyme class links monosaccharides?
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Glycotransferases
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What is a UDP Linkage?
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Di-phosphate linkage.
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What class of enzyme cleaves a Glycosidic Bond?
Examples? |
Glycosidases
Glycosidases hydrolyze glycosidic linkages to their reducing sugars Ex: Amylases digest polysaccharides (glycogen and starch) Disaccharidases digest disaccharides (maltose, sucrose, lactose) |
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What does Amylase break down?
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Glycogen and Starch
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What are examples of Disaccharidases?
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Sucrase:
Lactase Maltase, Iomaltase |
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Oral vs. Pancreatic Amylase
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Oral - Salivary glands during mastication
Pancreatic - From pancreatic juice in intestines Cleave: Alpha 1 -->4 Linkages Alpha-limited dextrins (have branches) Oligosaccharides Isomaltose Maltose |
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How can we absorb polysaccharides?
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We can't. We have to break it down into Monosaccharides for absorption to occur.
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Steps involved in carbohydrate digestion (sites of digestion).
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Mouth: Polysaccharides
Pancreas Duodenum: Disaccharides |
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What are the mechanisms for glucose, galactose, and fructose absorption from the small intestines?
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Into Intestinal Mucosal Cells
Na+ dependent transport: SGLT-1 GLUT-5: Fructose Into Blood GLUT-2 |
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Causes of Lactose Intolerance
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Primary: Lactase Deficiency
Secondary: Intestinal Injury First activity lost and last to recover |
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Glycogen Digestion by Amylase:
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1. Occurs in the mouth AND intestines
2. Part of the pancreatic juice 3. Hydrolyzes all the glycosidic linkages |
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Where does digestion of Maltose occur?
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Brush boarder of the small intestines
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Patients who are lactose intolerant cannot digest which linkages between which monomers?
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Beta Glycosidic linkages between Glucose and Galactose.
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Catabolic vs. Anabolic Pathways
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Catabolic (degradative)
Glycolysis and Beta-oxidation of fats Anabolic (Synthetic) Gluconeogenesis and Faty Acid Synthesis |
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Function of GLUT-1
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Transport glucose into Brain and RBC
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Function of GLUT-2
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Transport Glucose into the Liver
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Function of GLUT-4
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Transport Glucose into Muscle and Adipose Tissue
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Where is Glucokinase found?
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Liver Parenchymal Cells
Pancreatic Islet Cells |
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Characteristics of Pyruvate Kinase Deficiency
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Increase in 2,3 BPG
Lower than normal Oxygen affinity in the T-state Explanation: Dur to decreases in Glycolysis and therefore decrease in ATP production, one cannot maintain proper RBC membranes (NaK ATPase), which leads to hemolysis. |
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Allosteric Activators of Glycolysis
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AMP
Fructose 2,6 Bisphosphate |
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Allosteric Inhibitors of Glycolysis
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Citrate
ATP pH |
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Hormonal Effects on Glycolysis
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Insulin - Increases glycolysis
Glucagon - Decreases glycolysis |
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Irreversible Reactions in Glycolysis
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1. Hexokinase
2. Phosphofructokinase 3. Pyruvate Kinase |
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How can muscle lactate be reduced back to Hepatic Glucose?
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Cori Cycle
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Lactic Acidosis measurements of >5mM could indicate:
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1. MI
2. Pulmonary Embolism 3. Shock |
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PDHC Enzymes and Cofactors
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Enzymes - E1, E2, E3
Cofactors - 1. Thiamine Pyrophosphate (Vit B1) 2. Lipoic Adic 3. Coenzyme A - Pantothenic Acid 4. FAD+ - Riboflavin (Vit B2) 5. NAD+ - Niacin (Vit B3) |
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Allosteric Regulation of PDHC:
Inhibitors and Activators: |
Inhibitors:
ATP: well fed Acetyl-CoA: high product, more not needed NADH: high product, more not needed Activators: 1. Calcium: important during skeletal muscle contraction; allows for Acetyl-CoA to make more inputs for the ETC 2. High [Pyruvate]: high substrate |
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PDHC Deficiency
Cause, signs and symptoms, prognosis |
Cause: X-linked E1 alpha gene
Progression: 1. Less AcCoA made, so more Pyruvate accumulates 2. Lactic acid builds up. 3. Lethargy, poor feeding, tachypnea 4. Loss of ATP because the TCA cycle isn't doing anything Prognosis: Neurological problems are caused that can lead to death |
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Arsenic Poisoning
Causes and Progression |
Actions: Inhibits Lipoid Acid Containing Enzymes: PDH, alpha-ketoglutarate
Leads To: Increase in Pyruvate that becomes lactic acidosis Also: forms a complex that bypasses formation of 1,3-bisphosphoglycerate in glycolysis (which leads to a loss of ATP) |
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Importance of Citrate
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Inhibits PFK-1 in glycolysis (if there is enough citrate in the TCA cycle, then no more glycolysis needs to take place)
Source of Acetyl-CoA for Fatty Acid Synthesis Activates Acetyl-CoA Carboxylase |
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What happens when ATP and NADH are high?
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1. Citrate and Isocitrate accumulate
2. Acetyl-CoA is shuttled out of mitochondria via citrate for fat synthesis RESULT: High carb consumption leads to fat accumulation |
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What does Rat Poison do to Isocitrate?
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Inhibits Isocitrate because of the fluoroacetate in the rat poison
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Importance of Alpha-Ketoglutarate:
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Transamination: ALT
Oxidative deamination: GluDH |
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Importance of Succinyl-CoA
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Used to make heme
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Gluconeogenesis
Function, Location, Normal and Abnormal Blood Sugar Levels |
Function: Maintain blood Glucose Levels
Location: Liver and Kidney Cortex (mitochondria and cytosol) Blood Sugar Levels: Normal Fasting: 80-110mg/dl Hyperglygemic (diabetic) >126mg/dl |
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When the kidney is activated for gluconeogenesis, what is the preferred precursor?
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Glutamine
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Main Precursors for Gluconeogenesis
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1. Glycerol part from Triglycerides
2. Lactate from anaerobic metabolism of glucose 3. Gluconeogenic Amino Acid: Protein (Ala, Gln) |
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Why does Glycerol from triglycerides ast as a precursor for gluconeogenesis?
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The glycerol backbone of TG can produce DHAP, which is converted to G3P, which can go through gluconeogenesis
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How does Alanine get introduced to Gluconeogenesis?
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ALT converts Alanine to Pyruvate
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What are the 4 Enzymes in Gluconeogenesis that are needed to bypass irreversable reactions from glycolysis?
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1. Pyruvate Carboxylase
2. PEP Carboxylase (PEPCK) 3. Fructose 1,6-bisphosphatase 4. Glucose 6-Phosphatase |
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Steps in bypassing pyruvate kinase
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1. Pyruvate Carboxylase - carboxylates pyruvate to oxaloacetate
2. Oxaloacetate is converted to malate in order to make it out of the mitochondria. 3. Malate is converted back to oxaloacetate in the cytosol 4. PEPCK converts oxaloacetate to Phosphoenolpyruvate |
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What does PEPCK (Phosphoenolpyruvate Carboxykinase) do?
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Converts oxaloacetate to PEP
Requires GTP to make it |
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How does bypassing Fructose 1,6 Bisphosphate to get Glucose 6 phosphate work?
What stimulates and inhibits this step? |
Enzyme: Fructose 1,6-bisphosphatase
Stimulated by: Glucagon, High ATP Inhibited by: Fructose 2,6 Bisphosphate, High AMP |
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How does bypassing Glucose 6 Phosphate (hexokinase step) to get Glucose work?
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Enzyme: Glucose 6-Phosphatase
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Von Gierke Disease
Cause, Progression, Treatment: |
Type 1 Glycogen Storage Disease
Cause: Deficiency of Glucose 6-Phosphatase Causes severe hypoglycemia because free glucose cannot release to the blood Severe Lethargy, Seizures, Brain Damage can occur as a result Liver glycogen stores increase Hepatomegaly Hyperlipidemia and Hyperuricemia (high uric acid) Treatment: frequent meals so that one does not become hypoglycemic |
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PEPCK Deficiency
Cause, Presentation: |
Cause: Autosomal Recessive Trait
Presentation: 1. Hypoglycemia 2. Lactic Acidemia 3. Cerebral Atrophy 4. Fatty Liver |
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Fructose 1,6 Bisphosphatase Deficiency
Cause, Presentation: |
Cause: Rare autosomal Recessive
Presentation: 1. Hypoglycemia 2. Acidosis 3. Hypotonia: Lack of muscle tone 4. No Increase in glucose due to Glucagon 5. Glucagon --> Release of TG --> increase in glycerol --> excretion in urine |
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What is the effect of Ethanol on Gluconeogenesis?
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1. Ethanol is oxidized to acetaldehyde, which means reducing the cofactors to the effector enzymes (NAD+) to NADH.
2. Surplus of NADH is made, which inhibits the TCA cycle and forces LDH to be converted into Lactate instead of pyruvate. 3. Malate DH makes Malate instead of OAA, so there are less precursors to gluconeogenesis, and a subsequent drop in blood sugar. Low blood glucose leads to a rapid heart rate. 4. Lactic Acidosis leads to rapid breathing |
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What happens if you drink methanol?
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It is converted into Formaldehyde and you die or go blind.
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What are the different sources of blood glucose?
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1. Diet
2. Gluconeogenesis 3. Liver Glycogen |
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What is the first source of blood glucose during fasting?
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Liver Glycogen
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Structure of Glycogen
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Polymer of glucose (1,4 linkages) with glycosidic linkages being 1,6 linkages.
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What stimulates glycogenalysis in the muscle?
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1. Ca++ concentration
2. AMP 3. Epinepherine |
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Role of UDP Glucose
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Uradine diphosphate adds to a glucose monomer and hands it off to a Tyrosine residue that will accept the glucose onto the chain.
The UDP then associates with another glucose monomer. |
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Role of Glycogenin
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Protein to which glycogen attaches to initiate polymer.
Glycogen uses UDP glucose to autoglycosylate to the OH-Serine residue of glycogenin The polymer is extended using UDP glucose until it is long enough for the Glycogen Synthase enzyme. Glycogenin stays at the center of the completed glycogen molecule |
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Where does glycogen synthesis occur?
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Cytosol
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Advantages to the Branched structure of glycogen:
Forms a branched 1-6 linkage every 8 residues |
1. Increases the number of sites for synthesis and degradation
2. Increases the numebr of non-reducing ends available for degradation when needed 3. Increases the solubility: Amylopectin |
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Difference between amylose and amylopectin
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Amylose: Linear, unbranched chains of 100s of glucose residues (1-4 Linkage)
Amylopectin: Differs from amylose in being branched and more soluble |
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What is the role of 4:6 Transferase?
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Every 8 residues, it makes a branch (1-6 linkage), which can then be elongated
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How is glycogen synthesis regulated in the body?
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1. Allosteric: Glucose 6-P
2. Covalent (glucagon vs. Insulin) |
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How does Glucagon regulate glycogen synthesis?
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High glucagon (fasting state): less glycogen synthesis
Low blood glucose Increase phosphorylation: decrease in glycogen synthase activity |
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How does Insulin regulate glycogen synthesis?
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High Insulin: more glycogen synthesis
High blood glucose Decrease phosphorylation --> Increase in glycogen synthase activity |
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What happens when you activate Protein Kinase A?
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You inactivate glycogen synthesis because it phosphorylates glycogen synthase, inactivating it.
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GSD Type 0 (Glycogen Storage Disease 0)
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Etiology: Deficiency of glycogen synthase due to a mutation in Glycogen Synthase 2 (GYS2) gene
Autosomal Recessive Symptoms: Fasting hypoglycemia Treatment: Frequent meals and feeding uncooked cornstarch before bed because it is slow releasing glucose |
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GSD Type IV: Andersen Disease
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Also called Amylopectinosis
Etiology: Deficiency of glycogen branching enzyme (Glucosyl 4:6 transferase) Decrease in amylopectin branching leads to insolubility of glycogen because of long outer branches Symptoms: 1. Failure to thrive: growth and mental development 2. Enlarged liver and spleen 3. Progressive Cirrhosis 4. Muscle hypotonia 5. Death occurs typically before age 5 |
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What is the role of Calcium in Muscle?
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1. Ca++ is released from the SR during Muscle Contraction
2. Ca++ binds to the calmodulin subunit of Phosphorylase Kinase, activating it w/o Phosphorylation. 3. PK can then activate Glycogen Phosphorylase 4. #3 Causes Glycogen Degradation. |
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How do Glucagon (liver) and Epinepherine (muscle) affect Glycogenolysis?
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Triggers phosphorylation via cAMP and increases glycogenolysis
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How does Insulin affect Glycogenolysis?
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Triggers dephosphorylation of cAMP and inhibit glycogenolysis.
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What protein is needed to initiate glycogen synthesis?
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Glycogenin
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Under what state will the liver store glucose as glycogen?
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Well-fed State
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