Podcast
Questions and Answers
Which of the following enzymes is activated by Fructose-1,6-bisphosphate?
Which of the following enzymes is activated by Fructose-1,6-bisphosphate?
Which substance inhibits Phosphofructokinase-1 (PFK-1) under high energy conditions?
Which substance inhibits Phosphofructokinase-1 (PFK-1) under high energy conditions?
What is the net gain of ATP from glycolysis per molecule of glucose?
What is the net gain of ATP from glycolysis per molecule of glucose?
Which hormone decreases glycolysis in the liver and promotes the activation of AMP kinase?
Which hormone decreases glycolysis in the liver and promotes the activation of AMP kinase?
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Hexokinase is inhibited by which of the following?
Hexokinase is inhibited by which of the following?
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What is the primary product of glycolysis under aerobic conditions?
What is the primary product of glycolysis under aerobic conditions?
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Where does glycolysis occur within the cell?
Where does glycolysis occur within the cell?
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Which enzyme catalyzes the irreversible step of converting Glucose to Glucose-6-Phosphate?
Which enzyme catalyzes the irreversible step of converting Glucose to Glucose-6-Phosphate?
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Which of the following intermediates is produced when Dihydroxyacetone Phosphate is converted to Glyceraldehyde-3-Phosphate?
Which of the following intermediates is produced when Dihydroxyacetone Phosphate is converted to Glyceraldehyde-3-Phosphate?
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What inhibits Phosphofructokinase-1 during glycolysis?
What inhibits Phosphofructokinase-1 during glycolysis?
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Which step of glycolysis generates NADH?
Which step of glycolysis generates NADH?
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What is the role of Pyruvate Kinase in glycolysis?
What is the role of Pyruvate Kinase in glycolysis?
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Which tissue is especially reliant on glycolysis for quick energy during exercise?
Which tissue is especially reliant on glycolysis for quick energy during exercise?
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Study Notes
Glycolysis Overview
- Glycolysis is a metabolic pathway that converts glucose into pyruvate (or lactate anaerobically).
- It produces ATP and NADH.
- It occurs in the cytoplasm of cells.
- It's an anaerobic process (doesn't require oxygen).
- Crucial for rapid energy production, especially in muscle during exercise.
- Essential for various tissues, particularly muscle, red blood cells, and brain.
- The liver carries out glycolysis, especially during fasting (to produce and transport glucose).
Location and Intermediates
- Occurs in the cytoplasm.
- Some glycolysis intermediates (like pyruvate) are transported to the mitochondria for further metabolism.
Glycolysis Steps
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Glucose → Glucose-6-Phosphate (G6P):
- Enzyme: Hexokinase (or Glucokinase in liver).
- Irreversible step; traps glucose inside the cell.
- Regulated by: G6P (product inhibition), insulin (induces glucokinase), fructose-6-phosphate (inhibits glucokinase), and glucose-6-phosphate (inhibits hexokinase).
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Glucose-6-Phosphate → Fructose-6-Phosphate (F6P):
- Enzyme: Phosphoglucose Isomerase
- Reversible step
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Fructose-6-Phosphate → Fructose-1,6-Bisphosphate (F1,6BP):
- Enzyme: Phosphofructokinase-1 (PFK-1).
- Irreversible step; rate-limiting step of glycolysis. Consumes ATP.
- Regulated by: AMP, F2,6BP (activates), ATP, citrate, and H+ (inhibits).
-
Fructose-1,6-Bisphosphate → Glyceraldehyde-3-Phosphate (G3P) and Dihydroxyacetone Phosphate (DHAP):
- Enzyme: Aldolase.
- Reversible step
-
Dihydroxyacetone Phosphate → Glyceraldehyde-3-Phosphate (G3P):
- Enzyme: Triose Phosphate Isomerase
- Reversible step.
-
Glyceraldehyde-3-Phosphate → 1,3-Bisphosphoglycerate (1,3-BPG):
- Enzyme: Glyceraldehyde-3-Phosphate Dehydrogenase.
- Generates NADH by reducing NAD+.
- Reversible step
-
1,3-Bisphosphoglycerate → 3-Phosphoglycerate (3PG):
- Enzyme: Phosphoglycerate Kinase.
- Produces ATP (substrate-level phosphorylation).
- Reversible step.
-
3-Phosphoglycerate → 2-Phosphoglycerate (2PG):
- Enzyme: Phosphoglycerate Mutase
- Reversible step.
-
2-Phosphoglycerate → Phosphoenolpyruvate (PEP):
- Enzyme: Enolase.
- Reversible step.
-
Phosphoenolpyruvate → Pyruvate:
- Enzyme: Pyruvate Kinase.
- Irreversible step. Produces ATP.
- Regulated by: F1,6BP (activates), ATP, and Alanine (inhibits).
Irreversible Steps
- Glucose → G6P (hexokinase/glucokinase)
- F6P → F1,6BP (PFK-1)
- PEP → Pyruvate (pyruvate kinase)
Regulation of Glycolysis
-
Hormonal Regulation:
- Insulin: Activates glycolysis.
- Glucagon: Inhibits glycolysis.
-
Allosteric Regulation:
- PFK-1 is activated by AMP and F2,6BP, inhibited by ATP and citrate.
- Pyruvate kinase is activated by F1,6BP, inhibited by ATP and alanine.
- Hexokinase is inhibited by its product, G6P.
- Glucokinase (liver) is not inhibited by G6P, regulated by glucose availability.
-
Energetic Feedback:
- ATP and NADH accumulation inhibits further glycolysis.
- AMP and ADP stimulate glycolysis during low energy.
Energetic Summary
- Glycolysis produces 2 net ATP and 2 NADH per glucose molecule.
- NADH can be used in oxidative phosphorylation if oxygen is available.
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Description
This quiz focuses on the glycolysis metabolic pathway, which converts glucose into pyruvate, producing ATP and NADH. Explore important intermediates and enzymes involved in glycolysis, and understand its significance in energy production, especially during exercise and in various tissues. Test your knowledge of each step and its regulation.
