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Questions and Answers
What is the primary purpose of phosphorylating glucose in the cell?
What is the primary purpose of phosphorylating glucose in the cell?
- To effectively trap glucose as glucose 6-phosphate (correct)
- To allow glucose to diffuse out of the cell
- To promote the oxidation of pyruvate
- To release glucose into the bloodstream
How does the phosphorylation of glucose affect ATP production?
How does the phosphorylation of glucose affect ATP production?
- It has no impact on ATP production
- It produces 2 moles ATP per mole of glucose
- It produces 6 moles ATP per mole of glucose (correct)
- It reduces the amount of ATP produced
Which enzyme is primarily responsible for the phosphorylation of glucose in most tissues?
Which enzyme is primarily responsible for the phosphorylation of glucose in most tissues?
- Hexokinase I (correct)
- Pyruvate kinase
- Phosphofructokinase
- Glucose-6-phosphate dehydrogenase
What is a consequence of the lack of specific carriers for phosphorylated sugars?
What is a consequence of the lack of specific carriers for phosphorylated sugars?
What role does oxygen play in the process mentioned in the context of glucose phosphorylation?
What role does oxygen play in the process mentioned in the context of glucose phosphorylation?
What happens during the conversion of hexose to triose phosphate in glycolysis?
What happens during the conversion of hexose to triose phosphate in glycolysis?
What is a key characteristic of glucose 6-phosphate after phosphorylation?
What is a key characteristic of glucose 6-phosphate after phosphorylation?
Which statement about the ATP requirements during the conversion of hexose to triose phosphate is accurate?
Which statement about the ATP requirements during the conversion of hexose to triose phosphate is accurate?
What is a significant outcome of the oxidative decarboxylation of pyruvate?
What is a significant outcome of the oxidative decarboxylation of pyruvate?
What is the most common cause of enzyme deficiency-related hemolytic anemia?
What is the most common cause of enzyme deficiency-related hemolytic anemia?
What blood lactate level is indicative of lactic acidosis?
What blood lactate level is indicative of lactic acidosis?
What effect does hormonal regulation have on enzyme activity compared to short-term regulation?
What effect does hormonal regulation have on enzyme activity compared to short-term regulation?
Why do mature red blood cells (RBCs) rely entirely on glycolysis for ATP production?
Why do mature red blood cells (RBCs) rely entirely on glycolysis for ATP production?
Which process can lead to lactic acidosis?
Which process can lead to lactic acidosis?
What is the role of phosphorylation or dephosphorylation in glycolysis regulation?
What is the role of phosphorylation or dephosphorylation in glycolysis regulation?
What is the primary function of phosphofructokinase 1 (PFK-1) in glycolysis?
What is the primary function of phosphofructokinase 1 (PFK-1) in glycolysis?
Which of the following statements is true regarding the isomerization of glucose 6-phosphate?
Which of the following statements is true regarding the isomerization of glucose 6-phosphate?
What role does ATP play in the phosphorylation of fructose 6-phosphate?
What role does ATP play in the phosphorylation of fructose 6-phosphate?
Which enzyme catalyzes the cleavage of fructose 1,6-bisphosphate?
Which enzyme catalyzes the cleavage of fructose 1,6-bisphosphate?
In which tissues is the oxidative decarboxylation of pyruvate particularly important?
In which tissues is the oxidative decarboxylation of pyruvate particularly important?
What is the fate of pyruvate in the process of oxidative decarboxylation?
What is the fate of pyruvate in the process of oxidative decarboxylation?
What is the main regulatory factor for phosphofructokinase 1 activity?
What is the main regulatory factor for phosphofructokinase 1 activity?
Which reaction catalyzed by the pyruvate dehydrogenase complex is crucial for energy metabolism?
Which reaction catalyzed by the pyruvate dehydrogenase complex is crucial for energy metabolism?
What type of reaction is the cleavage of fructose 1,6-bisphosphate classified as?
What type of reaction is the cleavage of fructose 1,6-bisphosphate classified as?
How does aldolase function in the metabolism of dietary fructose?
How does aldolase function in the metabolism of dietary fructose?
What is the main function of pyruvate carboxylase in DHAP isomerization?
What is the main function of pyruvate carboxylase in DHAP isomerization?
Which of the following molecules is produced from the isomerization of DHAP?
Which of the following molecules is produced from the isomerization of DHAP?
What role does NAD+ play in glycolysis?
What role does NAD+ play in glycolysis?
Which of the following statements about anaerobic glycolysis is true?
Which of the following statements about anaerobic glycolysis is true?
What happens to pyruvate during the reduction to lactate?
What happens to pyruvate during the reduction to lactate?
Which enzyme catalyzes the reaction of pyruvate to alanine?
Which enzyme catalyzes the reaction of pyruvate to alanine?
How many ATP molecules are produced from anaerobic glycolysis per glucose molecule?
How many ATP molecules are produced from anaerobic glycolysis per glucose molecule?
In which process does pyruvate decarboxylase participate?
In which process does pyruvate decarboxylase participate?
What is the primary role of glyceraldehyde 3-phosphate oxidation in glycolysis?
What is the primary role of glyceraldehyde 3-phosphate oxidation in glycolysis?
What characterizes the energy yield of aerobic glycolysis compared to anaerobic glycolysis?
What characterizes the energy yield of aerobic glycolysis compared to anaerobic glycolysis?
What is the role of phosphoglycerate kinase in the glycolytic pathway?
What is the role of phosphoglycerate kinase in the glycolytic pathway?
Why does the liver require a high Km for glucose in certain conditions?
Why does the liver require a high Km for glucose in certain conditions?
Which enzyme catalyzes the shift of a phosphate group from carbon 3 to carbon 2?
Which enzyme catalyzes the shift of a phosphate group from carbon 3 to carbon 2?
What does the GLUT-2 transporter primarily facilitate?
What does the GLUT-2 transporter primarily facilitate?
What effect does a carbohydrate-rich diet have on glucose phosphorylation?
What effect does a carbohydrate-rich diet have on glucose phosphorylation?
Which of the following statements about pyruvate formation is true?
Which of the following statements about pyruvate formation is true?
Which compound is required for the conversion of 1,3-BPG into 3-PG?
Which compound is required for the conversion of 1,3-BPG into 3-PG?
What is the primary function of the lactate dehydrogenase enzyme in glycolysis?
What is the primary function of the lactate dehydrogenase enzyme in glycolysis?
What is the role of fructose-6-phosphate in glucose metabolism?
What is the role of fructose-6-phosphate in glucose metabolism?
Which statement accurately describes the process of minimizing hyperglycemia during the absorptive period?
Which statement accurately describes the process of minimizing hyperglycemia during the absorptive period?
Study Notes
Phosphorylation of Glucose
- Requires oxygen to reoxidize NADH produced during glyceraldehyde 3-phosphate oxidation.
- Irreversible process, effectively trapping glucose as glucose 6-phosphate, which is too polar to diffuse out of the cell.
- Produces 6 moles of ATP per mole of glucose.
Stages of Glycolysis
- Conversion of Hexose to Triose Phosphate
- 6-carbon sugar is cleaved into two 3-carbon sugars.
- Requires 2 moles of ATP for the hexose that is cleaved.
- ATP Formation from 1,3-Biphosphoglycerate
- Very specific for glucose; glucose sensor present in pancreatic β cells.
- Determines the threshold for insulin secretion, influenced by insulin and carbohydrate intake.
- The first glycolytic step generating ATP, catalyzed by phosphoglycerate kinase.
- Phosphate Group Shift from Carbon 3 to Carbon 2
- Catalyzed by phosphoglycerate mutase.
- 2-Phosphoglycerate Dehydration
- Catalyzed by enolase.
- Pyruvate Formation
- Third irreversible reaction of glycolysis, catalyzed by pyruvate kinase.
Regulation of Glycolysis
- Phosphofructokinase 1 (PFK-1) is a key regulatory enzyme, being rate-limiting and controlled by ATP, fructose 6-phosphate, and other effectors.
- Fructose 1,6-bisphosphate is cleaved by aldolase A in an unregulated reversible reaction.
Alternate Fates of Pyruvate
- Oxidative Decarboxylation to Acetyl CoA
- Important for high oxidative capacity tissues like cardiac muscle.
- Catalyzed by pyruvate dehydrogenase complex, provides fuel for the TCA cycle and fatty acid synthesis.
- Carboxylation to Oxaloacetate (OAA)
- Catalyzed by biotin-dependent pyruvate carboxylase, replenishing TCA cycle intermediates.
- Reduction to Ethanol (in Yeast and Certain Microorganisms)
- Involves decarboxylation and alcohol dehydrogenase reactions.
- Conversion to Alanine
- Links carbohydrate metabolism with amino acid metabolism, catalyzed by alanine aminotransferase.
- Reduction to Lactate
- Final product of anaerobic glycolysis.
Energy Yield of Glycolysis
- Anaerobic Glycolysis is significantly faster than aerobic glycolysis, providing ATP without oxygen.
- Overall reaction for anaerobic glycolysis produces 2 moles of lactate and ATP.
- Aerobic glycolysis results in 2 moles of pyruvate, ATP, and NADH.
Inherited Enzyme Deficiencies in Glycolysis
- Pyruvate Kinase Deficiency is the second most common cause of enzyme deficiency-related hemolytic anemia, primarily affecting erythrocytes.
- Other deficiencies include Glucose Phosphate Isomerase and Triose Phosphate Isomerase deficiencies.
Lactic Acidosis
- Blood lactate levels normally around 1.2 mM; lactic acidosis occurs at levels of 5 mM or more.
- Results from increased lactate formation or reduced utilization, leading to decreased blood pH and bicarbonate levels.
Hormonal Regulation of Glycolysis
- Short-term regulation involves allosteric mechanisms and phosphorylation status of key enzymes, impacting their activity quickly.
- Hormonal influences, by contrast, have slower but more significant effects, leading to substantial increases in enzyme activity over days.
Glycolysis and RBC Metabolism
- Mature red blood cells lack mitochondria and rely entirely on glycolysis for ATP production.
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Description
This quiz covers the process of glucose phosphorylation, including the requirement of oxygen to reoxidize NADH, and the mechanisms that effectively trap glucose as glucose 6-phosphate. Explore the irreversible steps involved in this essential biochemical reaction.
