64 Questions
What is the major pathway for glucose metabolism that occurs in the cytosol of all cells?
Glycolysis
Why do erythrocytes rely completely on glucose as their metabolic fuel?
Absence of mitochondria
Which enzyme system is required for glucose oxidation beyond pyruvate?
Pyruvate dehydrogenase complex
In which type of cells are elevated levels of GAPDH seen, potentially contributing to increased glycolysis?
Cancer cells
What is the fate of pyruvate in fast-growing cancer cells?
Reduced to lactate and exported
What causes lactic acidosis according to the text?
Impaired activity of pyruvate dehydrogenase
Which vitamin deficiency can lead to impaired pyruvate dehydrogenase activity?
Thiamin (vitamin B1)
What is the role of hexokinase in glycolysis according to the text?
Phosphorylates glucose to glucose-6-phosphate
What is the role of calcium ions in insulin secretion?
Promoting fusion of insulin secretory granules with the cell membrane
Which enzyme is involved in the conversion of glucose 6-phosphate to fructose 6-phosphate in glycolysis?
Phosphohexose isomerase
What is the significance of the reactions catalyzed by hexokinase, phosphofructokinase, and pyruvate kinase in glycolysis?
They are major sites of regulation in glycolysis
What metabolic consequence does phosphorylation of fructose to fructose 1-phosphate have in glycolysis?
Bypasses the main regulatory steps
Why is enolase inhibited by fluoride?
To interfere with the measurement of glucose in blood samples
What is the irreversible nature of pyruvate kinase reaction attributed to?
Formation of enol-pyruvate
Why does lactate dehydrogenase catalyze the reduction of pyruvate to lactate under anaerobic conditions?
To reoxidize NADH
What happens to pyruvate under aerobic conditions?
It is transported into mitochondria
What is the role of glucokinase in the liver?
Provide glucose for hepatic portal blood following a meal
How does glucokinase activity affect ATP levels in liver cells?
Increases ATP levels
What is the main function of hexokinase in the liver under normal conditions?
Synthesize glycogen and lipids
How does the closure of an ATP-potassium channel impact cellular function?
Causes membrane depolarization
What is the role of fructose 1-phosphate in glycolysis according to the text?
Bypasses the main regulatory steps
Which enzyme catalyzes the conversion of glucose 6-phosphate to fructose 6-phosphate in glycolysis?
Hexokinase
What does the fusion of insulin secretory granules with the cell membrane result in?
Release of insulin
Which compound is important at the junction of several metabolic pathways including Glycolysis and glycogenolysis?
Glucose 6-phosphate
What effect does fluoride have on enolase?
Inhibits it
Why is the reaction catalyzed by pyruvate kinase considered irreversible under physiological conditions?
Formation of enol-pyruvate
What happens to pyruvate under anaerobic conditions?
Reduced to lactate
What is the fate of NADH formed in glycolysis under aerobic conditions?
Transported into mitochondria for oxidation
What is the main factor that determines whether glycolysis can function aerobically or anaerobically?
Availability of oxygen
Why do erythrocytes rely completely on glucose as their metabolic fuel?
Lack of mitochondria
What might be a potential consequence of inhibiting GAPDH in cancer cells?
Reduced energy production
What is the significance of skeletal muscle performing glycolysis in the absence of oxygen?
Survival during anoxic episodes
Skeletal muscle can metabolize glucose both aerobically and anaerobically
True
Glucose is metabolized to fructose by the pathway of glycolysis
False
Acetyl-CoA can enter the citric acid cycle for complete oxidation to water and NADPH
False
Pyruvate is the precursor of fatty acids and cholesterol in the metabolic role of glucose
True
Glycogen is stored in skeletal muscle as a source of energy for muscle contraction.
True
In gluconeogenesis, substrates such as lactate and pyruvate enter the mitochondrion to yield acetyl-CoA for the synthesis of glucose.
False
The brain can meet about 50% of its energy needs from ketone bodies during prolonged fasting.
False
Most tissues, including the brain, have a substantial requirement for glucose as an energy source.
True
Glycolysis can only occur aerobically in cells with mitochondria.
False
Elevated levels of GAPDH in cancer cells lead to a decrease in glycolysis rates.
False
Methylglyoxal inhibits GAPDH in normal cells but not in cancer cells.
False
Skeletal muscle can perform glycolysis at very high levels of work output and survive anoxic episodes by utilizing oxygen efficiently.
False
In glycolysis, fructose 1-phosphate bypasses the main regulatory steps of glycolysis.
True
The reaction catalyzed by enolase in glycolysis involves a hydration reaction.
False
The reactions catalyzed by hexokinase, phosphofructokinase, and pyruvate kinase in glycolysis are freely reversible.
False
Increased lipogenesis in the liver and adipose tissue can be triggered by elevated levels of fructose in the diet.
True
What is the role of glucokinase in the liver, specifically?
Regulation of glucose levels in the hepatic portal blood
How is glucokinase activity linked to insulin secretion?
It increases ATP production leading to insulin release
What is the end product of glycolysis when it occurs anaerobically?
Lactate
What is one of the major functions of hexokinase in liver cells?
Phosphorylation of glucose to glucose-6-phosphate
In what way does glucokinase contribute to lipogenesis?
By enhancing the synthesis of fatty acids for storage
Which process utilizes glucose to provide reducing equivalents (NADPH) for fatty acid synthesis?
Pentose phosphate pathway
What is the main metabolic role of acetyl-CoA in glucose metabolism?
Fatty acid synthesis
Which component of skeletal muscle metabolism can occur in the absence of oxygen?
Utilization of glucose as fuel
Which enzyme is responsible for converting fructose to fructose 1-phosphate in glycolysis?
Glucokinase
What is the main site of regulation in glycolysis that involves irreversible reactions?
Phosphofructokinase
How does the phosphorylation of fructose to fructose 1-phosphate affect glycolysis?
Bypasses regulatory steps
Which compound plays a critical role at the intersection of several metabolic pathways including glycolysis, glycogenesis, and glycogenolysis?
Glucose 6-phosphate
Why is the reaction catalyzed by enolase considered crucial in glycolysis?
It transfers phosphate to ADP in substrate-level phosphorylation
What is the main reason for the irreversible nature of pyruvate kinase reaction under physiological conditions?
The large free energy change involved
Why is NADH reduced to lactate under anaerobic conditions and not reoxidized through the respiratory chain?
To permit oxidation of NADH
What is the fate of pyruvate under aerobic conditions in liver glycolysis?
Conversion to acetyl-CoA for citric acid cycle
Explore the process of insulin release due to calcium influx and the role of glucose 6-phosphate in various metabolic pathways. Understand the conversion of glucose 6-phosphate to fructose 6-phosphate in glycolysis. Test your knowledge of carbohydrates metabolism.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
