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Questions and Answers
What is a unique aspect of fructose metabolism?
What is a unique aspect of fructose metabolism?
- It is metabolized at a slower rate than glucose (correct)
- It is ultimately converted to galactose
- It is phosphorylated by hexokinase in adipose cells
- It is cleaved by a specific Enolase
What is a unique aspect of fructose metabolism?
What is a unique aspect of fructose metabolism?
- Lactate
- 1,3-bisphosphoglycerate
- Pyruvate
- 2,3-bisphosphoglycerate (correct)
- It is metabolized at a slower rate than glucose (correct)
- It is ultimately converted to galactose
- It is phosphorylated by hexokinase in adipose cells
- It is cleaved by a specific Enolase
What is the primary reason for decreased metabolic energy in poorly perfused areas exposed to chronic hypoxia?
What is the primary reason for decreased metabolic energy in poorly perfused areas exposed to chronic hypoxia?
- Decreased respiratory quotient
- Increased glucose utilization by HMP pathway
- Increased hexokinase activity
- Decreased ATP production and increased glucose utilization (correct)
What is the liver metabolite of alcohol that is associated with a genetic variation in an enzyme?
What is the liver metabolite of alcohol that is associated with a genetic variation in an enzyme?
What type of reaction is catalyzed by the enzyme that uses inorganic phosphate?
What type of reaction is catalyzed by the enzyme that uses inorganic phosphate?
What is a characteristic of anaerobic glycolysis in poorly perfused areas?
What is a characteristic of anaerobic glycolysis in poorly perfused areas?
In a tissue that metabolizes glucose via the pentose phosphate pathway, where would C-1 of glucose be expected to end up principally?
In a tissue that metabolizes glucose via the pentose phosphate pathway, where would C-1 of glucose be expected to end up principally?
How many ATPs are derived when glucose is converted to lactate by anaerobic glycolysis?
How many ATPs are derived when glucose is converted to lactate by anaerobic glycolysis?
Which of the following statements is incorrect about the condition when one molecule of glucose is oxidized to 2 molecules of lactate during anaerobic glycolysis?
Which of the following statements is incorrect about the condition when one molecule of glucose is oxidized to 2 molecules of lactate during anaerobic glycolysis?
What is the equivalent of ATPs derived when glucose is completely oxidized to CO2 by glycolysis, Pyruvate dehydrogenase, and the TCA cycle?
What is the equivalent of ATPs derived when glucose is completely oxidized to CO2 by glycolysis, Pyruvate dehydrogenase, and the TCA cycle?
Which of the following is not a reason for Lactic Acidosis?
Which of the following is not a reason for Lactic Acidosis?
What is the primary cause of Lactic Acidosis in cases where there is not enough oxygen to satisfy the needs of oxidative phosphorylation?
What is the primary cause of Lactic Acidosis in cases where there is not enough oxygen to satisfy the needs of oxidative phosphorylation?
What is the purpose of reducing pyruvate to lactate?
What is the purpose of reducing pyruvate to lactate?
What occurs under anaerobic conditions in relation to pyruvate?
What occurs under anaerobic conditions in relation to pyruvate?
What step is not involved in the conversion of glyceraldehyde 3-phosphate to 3-phosphoglycerate?
What step is not involved in the conversion of glyceraldehyde 3-phosphate to 3-phosphoglycerate?
What is the result of the oxidation of 3 mol of glucose by the pentose phosphate pathway?
What is the result of the oxidation of 3 mol of glucose by the pentose phosphate pathway?
How many ATP molecules can be derived from each molecule of acetyl CoA that enters the Krebs' Cycle?
How many ATP molecules can be derived from each molecule of acetyl CoA that enters the Krebs' Cycle?
Why is phosphofructokinase rather than hexokinase the pacemaker of Glycolysis?
Why is phosphofructokinase rather than hexokinase the pacemaker of Glycolysis?
Which enzyme uses NAD+ and dihydroxyacetone phosphate as substrates?
Which enzyme uses NAD+ and dihydroxyacetone phosphate as substrates?
What is the product of the enzyme that catalyzes the first substrate level phosphorylation in glycolysis?
What is the product of the enzyme that catalyzes the first substrate level phosphorylation in glycolysis?
Which statement about the Lactate dehydrogenase (LDH) reaction is true?
Which statement about the Lactate dehydrogenase (LDH) reaction is true?
What determines whether a cell oxidizes glucose by aerobic glycolysis or by anaerobic glycolysis?
What determines whether a cell oxidizes glucose by aerobic glycolysis or by anaerobic glycolysis?
What is the substrate of the enzyme that catalyzes the second substrate level phosphorylation of glycolysis?
What is the substrate of the enzyme that catalyzes the second substrate level phosphorylation of glycolysis?
Which enzyme is not involved in the glycolytic pathway?
Which enzyme is not involved in the glycolytic pathway?
Which citrate function is related to fatty acid synthesis?
Which citrate function is related to fatty acid synthesis?
Which of the following is NOT a favorable regulator for gluconeogenesis from pyruvate?
Which of the following is NOT a favorable regulator for gluconeogenesis from pyruvate?
Which metabolic pathway is found exclusively in the cytosol?
Which metabolic pathway is found exclusively in the cytosol?
Why is it crucial to feed the baby soon after birth?
Why is it crucial to feed the baby soon after birth?
Why can't humans utilize cellulose as a source of glucose?
Why can't humans utilize cellulose as a source of glucose?
What is the primary function of oxaloacetate?
What is the primary function of oxaloacetate?
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Study Notes
Fructose Metabolism
- Fructose is metabolized faster than glucose.
- After an initial modification, fructose is cleaved by a specific enzyme, enolase.
- Final product of fructose metabolism ultimately converts to galactose.
- Hexokinase can phosphorylate fructose in adipose tissue.
Glycolytic Products and Erythrocytes
- Erythrocytes primarily produce 2,3-bisphosphoglycerate, essential for oxygen unloading to tissues.
- Poorly perfused areas experience decreased ATP production and increased glucose utilization due to anaerobic glycolysis.
Ethanol Metabolism and Genetic Response
- Certain ethnic groups, such as Asians and Native Americans, may experience flushing and illness after small amounts of ethanol due to genetic variations affecting acetaldehyde metabolism.
Glycolysis and ATP Generation
- Anaerobic glycolysis from one glucose molecule yields 2 ATP; complete oxidation yields up to 38 ATP.
- During anaerobic glycolysis, ATP is consumed in the phosphofructokinase and hexokinase reactions, while ATP is produced in the pyruvate kinase reaction.
Lactic Acidosis Conditions
- Factors leading to lactic acidosis include high altitude, heart failure, inadequate oxygen for oxidative phosphorylation, and inhibition of the electron transport chain.
Pentose Phosphate Pathway
- Metabolic processing of glucose through the pentose phosphate pathway primarily channels C-1 of glucose into carbon dioxide.
TCA Cycle and ATP Production
- Each acetyl CoA entering the Krebs cycle can yield approximately 12 ATP.
- Key vitamins, including pantothenic acid, lipoic acid, and riboflavin, are involved in TCA cycle reactions; folic acid does not participate.
Key Enzymatic Reactions in Glycolysis
- Phosphofructokinase is the primary regulator of glycolysis.
- Glyceraldehyde-3-phosphate dehydrogenase converts a triose phosphate to produce NADH.
- Substrate-level phosphorylation occurs at various steps in glycolysis, primarily through phosphoglycerate kinase and pyruvate kinase.
Lactate Dehydrogenase Role
- Lactate dehydrogenase catalyzes the reversible reaction converting pyruvate to lactate, regenerating NAD+ under anaerobic conditions.
Factors Influencing Glycolytic Pathway
- Cells determine glycolytic pathway—aerobic or anaerobic—based on oxygen levels and mitochondrial count.
Gluconeogenesis and Substrate Concentration
- High levels of acetyl CoA, NADH, ATP, and citrate promote gluconeogenesis, while fructose 2,6-bisphosphate does not.
Exclusive Cytosolic Pathways
- Glycolysis, gluconeogenesis from pyruvate, and the pentose phosphate pathway occur exclusively in the cytosol.
Post-Birth Metabolism Considerations
- Newborns need timely feeding as low levels of phosphoenolpyruvate carboxykinase compromise gluconeogenesis.
Fiber Metabolism
- Humans cannot digest cellulose due to the absence of enzymes required to break down beta-1,4 O-glycosidic linkages.
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