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Questions and Answers
What is produced during glycolysis?
What is produced during glycolysis?
Glycolysis occurs in the mitochondria of the cell.
Glycolysis occurs in the mitochondria of the cell.
False
Name the enzyme responsible for converting Glyceraldehyde-3-phosphate to 1,3-Bisphosphoglycerate.
Name the enzyme responsible for converting Glyceraldehyde-3-phosphate to 1,3-Bisphosphoglycerate.
Glyceraldehyde-3-Phosphate Dehydrogenase
In the preparatory phase of glycolysis, Glucose is phosphorylated to __________.
In the preparatory phase of glycolysis, Glucose is phosphorylated to __________.
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Match the following glucose transporters with their primary location:
Match the following glucose transporters with their primary location:
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Which statement accurately describes the regulation of Phosphofructokinase-1 (PFK-1)?
Which statement accurately describes the regulation of Phosphofructokinase-1 (PFK-1)?
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Anaerobic glycolysis results in the production of pyruvate only.
Anaerobic glycolysis results in the production of pyruvate only.
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What is the net yield of ATP from one molecule of glucose during glycolysis?
What is the net yield of ATP from one molecule of glucose during glycolysis?
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In the payoff phase of glycolysis, NADH is produced during the conversion of __________ to 1,3-Bisphosphoglycerate.
In the payoff phase of glycolysis, NADH is produced during the conversion of __________ to 1,3-Bisphosphoglycerate.
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Which enzyme catalyzes the final step of glycolysis, converting PEP to Pyruvate?
Which enzyme catalyzes the final step of glycolysis, converting PEP to Pyruvate?
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Study Notes
Glycolysis
- Glycolysis is the breakdown of glucose to produce pyruvate and energy in the form of ATP
- Glucose is a key fuel source for the body
- Glucose can be stored in polymeric form as glycogen
- Glucose can be synthesized via Gluconeogenesis (a separate topic)
- Glycolysis occurs in the cytoplasm of the cell
- Glucose enters the cell via GLUT transporters, each with specific tissue expression:
- GLUT1: red blood cells, blood-brain barrier, placenta
- GLUT2: liver, pancreatic islets, small intestine, kidney
- GLUT3: brain (neurons), testes
- GLUT4: skeletal and heart muscle, fat
- Glycolysis is divided into two phases: preparatory and payoff phases
Preparatory phase (Steps 1-5)
- Preparatory phase requires ATP input
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Step 1: Glucose is phosphorylated to Glucose-6-phosphate (irreversible)
- Requires enzyme Hexokinase (four isozymes encoded by different genes):
- Muscle: Hexokinase 1 and 2
- Liver: Hexokinase 4 (also known as Glucokinase)
- Requires enzyme Hexokinase (four isozymes encoded by different genes):
-
Step 2: Glucose-6-phosphate is isomerized to Fructose-6-phosphate (reversible)
- Requires enzyme Phosphohexose Isomerase
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Step 3: Fructose-6-phosphate is phosphorylated to Fructose-1,6-Bisphosphate
- Requires enzyme Phosphofructokinase-1 (PFK-1)
- PFK-1 is allosterically regulated by ATP and AMP levels:
- High ATP: PFK-1 is inhibited
- Low ATP: PFK-1 is activated
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Step 4: Fructose-1,6-bisphosphate is split into two 3-carbon sugars:
- Dihydroxyacetone phosphate (DHAP) and Glyceraldehyde-3-phosphate
- Requires enzyme Aldolase
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Step 5: Dihydroxyacetone phosphate (DHAP) is converted to Glyceraldehyde-3-phosphate (reversible)
- Requires enzyme Triose Phosphate Isomerase
- Glyceraldehyde-3-phosphate is the only sugar that can continue through glycolysis
Payoff Phase (Steps 6-10)
- Payoff phase produces NADH and ATP
-
Step 6: Glyceraldehyde-3-phosphate is oxidized to 1,3-Bisphosphoglycerate
- Requires enzyme Glyceraldehyde-3-Phosphate Dehydrogenase
- NAD+ is reduced to NADH
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Step 7: 1,3-Bisphosphoglycerate is converted to 3-Phosphoglycerate (reversible)
- Requires enzyme Phosphoglycerate Kinase
- Phosphate group is transferred to ADP, producing 1 ATP
- Step 8: 3-Phosphoglycerate is converted to 2-Phosphoglycerate
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Step 9: 2-Phosphoglycerate is converted to Phosphoenolpyruvate (PEP) (dehydration reaction)
- Requires enzyme Enolase
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Step 10: Phosphoenolpyruvate (PEP) is converted to Pyruvate (irreversible)
- Requires enzyme Pyruvate Kinase
- Phosphate group is transferred to ADP, producing 1 ATP
Glycolysis Summary and Products
- Investment in the preparatory phase: 2 ATP
- Production in the payoff phase: 2 pyruvate, 2 NADH, 4 ATP
- Net yield per 1 glucose molecule: 2 ATP and 2 NADH
Glycolysis in Aerobic or Anaerobic Conditions
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Aerobic Conditions: Pyruvate is oxidized to Acetyl-CoA and CO2
- Acetyl-CoA enters the Citric Acid Cycle
- NADH is re-oxidized to NAD+ by donating electrons to the electron transport chain (producing ATP)
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Anaerobic Conditions: NADH donates electrons to pyruvate, converting it to lactate
- This reaction is catalyzed by lactate dehydrogenase
- NADH is re-oxidized to NAD+, maintaining the supply of NAD+ for glycolysis to continue
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Description
This quiz covers the process of glycolysis, including the breakdown of glucose to produce pyruvate and energy in the form of ATP. It details the phases of glycolysis, the enzymes involved, and how glucose is transported into the cell. Test your understanding of this crucial metabolic pathway.
