Questions and Answers
Which enzyme is NOT involved in bypassing the irreversible reactions of gluconeogenesis?
During fasting, which hormone's release primarily promotes gluconeogenesis?
What condition is commonly associated with an accumulation of cytoplasmic NADH in alcoholics?
Which pathway initiates the conversion of glucose to sorbitol?
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What is the outcome of Fructose Aldolase B deficiency?
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What process is triggered by an increase in insulin in the cell?
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What is the primary function of pancreatic amylase?
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Which enzyme is associated with high affinity for fructose-6-phosphate (F6-P) in the presence of ATP?
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What is the consequence of pyruvate kinase deficiency in red blood cells (RBC)?
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Which type of digestion is completed via brush border enzymes?
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What does Hexokinase convert glucose into?
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Which enzyme is considered the rate-limiting enzyme of the Krebs cycle?
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What are the primary products of the Pyruvate Dehydrogenase (PDH) reaction?
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Which compound does Cyanide bind irreversibly to?
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What is the role of uncoupling proteins found in brown adipose tissue?
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Which substances are precursors for gluconeogenesis?
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Which of the following increases ADP activation in the Krebs cycle?
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What is the effect of a decreased ATP concentration on PDH activity?
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What primary role does glycogen synthase play in glycogenesis?
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Which enzymes are involved in the debranching of glycogen?
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What trigger is associated with glucose-6-phosphate dehydrogenase (G6PD) deficiency leading to hemolysis?
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How does insulin affect glycogen synthase activity?
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What is the result of a deficiency in glucose-6-phosphatase?
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What enzyme catalyzes the synthesis of nitric oxide (NO)?
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Which compound is primarily used as a substrate in glycogenesis?
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What process is glucose-6-phosphate involved in when discussing RBC capability?
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Study Notes
Enzyme Functions in Metabolism
- Phosphorylase adds phosphate from ATP; Phosphatase removes phosphate.
- GLUT-4 is an insulin-dependent transporter; increased insulin stimulates its exocytosis.
- Intraluminal digestion occurs via pancreatic amylase breaking down polysaccharides to disaccharides; final digestion at the brush border.
Key Enzymes in Glycolysis and Their Functions
- Glucokinase is present in most tissues; Hexokinase is specific to liver and pancreatic beta cells, with dependent ATP levels.
- Pyruvate Kinase deficiency leads to ineffective ATP production, causing hemolytic anemia due to premature RBC destruction.
Irreversible Steps of Glycolysis
- Key regulatory enzymes include Hexokinase, PFR (Phosphofructokinase-1), and Pyruvate Kinase.
- PFR is the rate-limiting enzyme for glycolysis, facilitating conversion from Fructose 6-phosphate to Fructose 1,6-bisphosphate.
Krebs Cycle Overview
- Occurs in mitochondrial matrix; generates 3 NADH, FADH2, GTP, and releases 2 CO2.
- Isocitrate Dehydrogenase serves as the primary rate-limiting enzyme.
Metabolic Pathways and Interactions
- Lipoic acid is involved in converting alpha-ketoglutarate to succinyl-CoA.
- Cyanide poisoning irreversibly inhibits complex IV of the ETC, reducing ATP and oxygen levels.
Uncoupling Proteins
- Found in brown adipose tissue, facilitate thermogenesis, influenced by ADP, enhancing both ETC and Krebs cycle activity.
Gluconeogenesis Essentials
- Precursors include glycerol, lactate, and amino acids; primarily occurs in the liver and kidneys.
- Bypasses irreversible reactions in gluconeogenesis require Pyruvate Kinase, PFR-1, and Glucose-6-Phosphatase.
Hormonal Regulation
- Increased ATP favors glycolysis while promoting gluconeogenesis.
- Glucagon stimulates gluconeogenesis, while insulin inhibits glycogen synthesis and promotes glucose uptake.
NADH Generation and Importance
- Excess NADH can lead to hypoglycemia in alcoholics by promoting an imbalance in cellular redox states.
- Glucose-6-Phosphate Dehydrogenase deficiency can lead to hemolysis, especially under stress like infection or exposure to oxidants.
Glycogen Metabolism
- Glycogen synthesis is catalyzed by glycogen synthase; glycogen phosphorylase is inhibited by insulin and activated by glucagon and epinephrine.
- Lack of glycogen phosphorylase results in McArdle disease; Von Gierke's disease is caused by a deficiency in Glucose-6-Phosphatase.
Additional Metabolic Insights
- The Polyol pathway converts glucose to sorbitol via aldose reductase and sorbitol to fructose via sorbitol dehydrogenase, linked to peripheral neuropathy and cataracts.
- Classic Galactosemia is associated with a deficiency in uridyltransferase, affecting galactose metabolism.
NADPH Role in Cellular Functions
- NADPH is crucial for synthesizing nitric oxide, essential for immune response and vascular regulation.
- G6PD deficiency diminishes the RBC's ability to generate NADPH, leading to hemolysis under oxidative stress.
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Description
This quiz covers the roles of phosphorylase and phosphatase in relation to insulin, as well as the process of exocytosis and intraluminal digestion. Test your knowledge on how insulin affects GLUT-4 receptors and the function of pancreatic amylase in polysaccharide digestion.
