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Questions and Answers
The pathway of ______ breaks down glucose into two 3-carbon pyruvate molecules.
The pathway of ______ breaks down glucose into two 3-carbon pyruvate molecules.
glycolysis
Under anaerobic conditions, glycolysis produces ______ instead of pyruvate.
Under anaerobic conditions, glycolysis produces ______ instead of pyruvate.
lactate
Erythrocytes, or red blood cells, rely solely on ______ for their energy production.
Erythrocytes, or red blood cells, rely solely on ______ for their energy production.
glycolysis
The enzyme ______ catalyzes the phosphorylation of glucose to glucose-6-phosphate in the first step of glycolysis.
The enzyme ______ catalyzes the phosphorylation of glucose to glucose-6-phosphate in the first step of glycolysis.
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The enzyme glucokinase, unlike hexokinase, is regulated by ______.
The enzyme glucokinase, unlike hexokinase, is regulated by ______.
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The phosphorylation of glucose by hexokinase is an ______ reaction.
The phosphorylation of glucose by hexokinase is an ______ reaction.
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Glucose-6-phosphate can be converted to ______ by phosphohexose isomerase in the second step of glycolysis.
Glucose-6-phosphate can be converted to ______ by phosphohexose isomerase in the second step of glycolysis.
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In diabetes mellitus, insulin deficiency hinders the entry of glucose into ______ cells.
In diabetes mellitus, insulin deficiency hinders the entry of glucose into ______ cells.
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The enzyme ______ is responsible for converting glucose-6-phosphate to fructose-6-phosphate.
The enzyme ______ is responsible for converting glucose-6-phosphate to fructose-6-phosphate.
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Fructose-1,6-bisphosphate is cleaved into two 3-carbon units, one of which is ______.
Fructose-1,6-bisphosphate is cleaved into two 3-carbon units, one of which is ______.
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The enzyme ______ catalyzes the isomerization of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate.
The enzyme ______ catalyzes the isomerization of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate.
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Glyceraldehyde-3-phosphate is ______ and phosphorylated to 1,3-bisphosphoglycerate.
Glyceraldehyde-3-phosphate is ______ and phosphorylated to 1,3-bisphosphoglycerate.
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The energy released from 1,3-bisphosphoglycerate is utilized to synthesize ATP in a process known as ______.
The energy released from 1,3-bisphosphoglycerate is utilized to synthesize ATP in a process known as ______.
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The enzyme ______ catalyzes the isomerization of 3-phosphoglycerate to 2-phosphoglycerate by shifting the phosphate group.
The enzyme ______ catalyzes the isomerization of 3-phosphoglycerate to 2-phosphoglycerate by shifting the phosphate group.
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The enzyme ______ removes a water molecule from 2-phosphoglycerate to produce phosphoenolpyruvate.
The enzyme ______ removes a water molecule from 2-phosphoglycerate to produce phosphoenolpyruvate.
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Phosphoenolpyruvate is dephosphorylated to ______ by pyruvate kinase, generating ATP.
Phosphoenolpyruvate is dephosphorylated to ______ by pyruvate kinase, generating ATP.
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In anaerobic conditions, pyruvate is reduced to ______ by lactate dehydrogenase.
In anaerobic conditions, pyruvate is reduced to ______ by lactate dehydrogenase.
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The enzyme ______ is an important regulatory enzyme in glycolysis.
The enzyme ______ is an important regulatory enzyme in glycolysis.
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Flashcards
Glycolysis
Glycolysis
The pathway that splits glucose into two pyruvate molecules for energy production.
Location of Glycolysis
Location of Glycolysis
Glycolysis occurs in the cytoplasm of cells.
Energy Source in Erythrocytes
Energy Source in Erythrocytes
Glycolysis is the only energy source for red blood cells.
Anaerobic Glycolysis
Anaerobic Glycolysis
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Hexokinase
Hexokinase
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GluT4
GluT4
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Glucose-6-Phosphate
Glucose-6-Phosphate
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Reversibility in Glycolysis
Reversibility in Glycolysis
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Fructose-6-phosphate to Fructose-1,6-bisphosphate
Fructose-6-phosphate to Fructose-1,6-bisphosphate
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Phosphofructokinase (PFK)
Phosphofructokinase (PFK)
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Rate limiting step in glycolysis
Rate limiting step in glycolysis
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Aldolase
Aldolase
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Glyceraldehyde-3-phosphate (G3P)
Glyceraldehyde-3-phosphate (G3P)
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Glyceraldehyde-3-phosphate dehydrogenase
Glyceraldehyde-3-phosphate dehydrogenase
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Substrate-level phosphorylation
Substrate-level phosphorylation
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Enolase
Enolase
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Pyruvate kinase
Pyruvate kinase
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Lactate dehydrogenase (LDH)
Lactate dehydrogenase (LDH)
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Study Notes
Glycolysis (Embden-Meyerhof Pathway)
- Definition: Glucose is split into two pyruvate molecules (or lactate under anaerobic conditions) releasing small amounts of energy.
- Location: All steps occur in the cytoplasm.
- Significance:
- Universal pathway in all cells.
- Primary energy source for red blood cells.
- Important energy source for muscle during strenuous activity (anaerobic glycolysis).
- Precursor to complete glucose oxidation.
- Provides carbon skeletons for non-essential amino acids and glycerol in fats.
- Many reactions are reversible, crucial for gluconeogenesis.
Glucose Entry into Cells
- Transport: Glucose transporter-4 (GLUT4) moves glucose from the extracellular fluid into muscle and adipose cells. Insulin regulates GLUT4. GLUT2 is the transporter in liver cells and is not insulin-dependent.
- Diabetes: Insulin deficiency in diabetes hinders glucose entry into peripheral cells.
Glycolysis Steps (Detailed)
Step 1: Glucose Phosphorylation
- Action: Glucose is phosphorylated to glucose-6-phosphate.
- Enzyme: Hexokinase.
- Mechanism: Hexokinase uses ATP energy to add a phosphate group to glucose. ATP is converted to ADP in the process.
- Irreversibility: A key regulatory step in glycolysis.
- Alternative Enzyme: Glucokinase (insulin-dependent, distinct from hexokinase).
- Fate of Glucose-6-Phosphate: Trapped in the cell for metabolism.
Step 2: Glucose-6-Phosphate Isomerization
- Action: Glucose-6-phosphate is converted to fructose-6-phosphate.
- Enzyme: Phosphohexose isomerase.
- Reversible: The reaction can readily proceed in either direction.
Step 3: Fructose-6-Phosphate Phosphorylation
- Action: Fructose-6-phosphate is phosphorylated to fructose-1,6-bisphosphate.
- Enzyme: Phosphofructokinase (PFK).
- Mechanism: PFK utilizes ATP to phosphorylate, converting it to ADP.
- Regulation: A key regulatory enzyme, irreversible.
- Gluconeogenesis Bypass: This step is bypassed during gluconeogenesis using fructose-1,6-bisphosphatase.
- Preparatory Phase: Steps 1, 2, and 3 collectively.
Step 4: Fructose-1,6-Bisphosphate Cleavage
- Action: Six-carbon fructose-1,6-bisphosphate is split into two three-carbon molecules: glyceraldehyde-3-phosphate and dihydroxyacetone phosphate (DHAP).
- Enzyme: Aldolase.
- Reversible: The reaction proceeds in either direction.
Step 4-A: Dihydroxyacetone Phosphate Isomerization
- Action: DHAP is converted to glyceraldehyde-3-phosphate.
- Enzyme: Triose phosphate isomerase.
- Net Result: Glucose is split into two molecules of glyceraldehyde-3-phosphate.
- Glycerol Entry/Fat Synthesis: Glycerol can enter the glycolytic/gluconeogenic pathway from neutral fats. DHAP is a link.
Step 5: Glyceraldehyde-3-Phosphate Oxidation
- Action: Glyceraldehyde-3-phosphate is dehydrogenated and phosphorylated to 1,3-bisphosphoglycerate.
- Enzyme: Glyceraldehyde-3-phosphate dehydrogenase.
- Mechanism: Oxidizes aldehyde, forming a high-energy phosphate bond in 1,3-bisphosphoglycerate; uses NAD+ as cofactor, reducing it to NADH.
- Reversible: Reaction can proceed in either direction.
Step 6: 1,3-Bisphosphoglycerate to ATP
- Action: 1,3-bisphosphoglycerate's energy is used to produce ATP via substrate-level phosphorylation.
- Enzyme: Bisphosphoglycerate kinase.
- Substrate-Level Phosphorylation: ATP generated directly from the substrate, not the electron transport chain.
- Oxidative Phosphorylation: Synthesis from oxidation, involving electron transport chain.
- Reversible: Reaction can proceed in either direction.
Step 7: 3-Phosphoglycerate Isomerization
- Action: 3-phosphoglycerate is converted to 2-phosphoglycerate by shifting the phosphate group.
- Enzyme: Phosphoglycerate mutase.
- Reversible: Reaction can proceed in either direction.
Step 8: 2-Phosphoglycerate to Phosphoenolpyruvate
- Action: 2-phosphoglycerate is converted to phosphoenolpyruvate (PEP) by dehydration.
- Enzyme: Enolase.
- Mg++ Requirement: Magnesium ions are needed for the enzyme activity.
- Fluoride Inhibition: Fluoride inhibits enolase, stopping glycolysis (used in blood sugar tests).
- Reversible: Reaction can proceed in either direction.
Step 9: Phosphoenolpyruvate to Pyruvate
- Action: PEP is dephosphorylated to pyruvate.
- Enzyme: Pyruvate kinase.
- Mechanism: ATP is generated by substrate-level phosphorylation.
- Key Enzyme: Key regulatory step in glycolysis.
- Irreversible: The reaction cannot readily proceed in reverse during gluconeogenesis.
Step 10: Pyruvate Reduction (Anaerobic)
- Action: Under anaerobic conditions, pyruvate is reduced to lactate.
- Enzyme: Lactate dehydrogenase (LDH).
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Description
Test your knowledge on the glycolysis pathway, detailing how glucose is converted into pyruvate and the role of glucose transporters in cells. This quiz also covers the significance of glycolysis in metabolism and its implications in diabetes. Perfect for students studying biochemistry or related fields.
