Podcast
Questions and Answers
What product is formed from 1,3-bisphosphoglycerate in RBCs during glycogenesis?
What product is formed from 1,3-bisphosphoglycerate in RBCs during glycogenesis?
Which enzyme hydrolyzes 2,3-bisphosphoglycerate in RBCs?
Which enzyme hydrolyzes 2,3-bisphosphoglycerate in RBCs?
What is the main product of the isomerization of dihydroxyacetone phosphate?
What is the main product of the isomerization of dihydroxyacetone phosphate?
What is the effect of 2,3-bisphosphoglycerate on hemoglobin?
What is the effect of 2,3-bisphosphoglycerate on hemoglobin?
Signup and view all the answers
Which enzyme is primarily affected by pyruvate kinase deficiency in terms of energy production?
Which enzyme is primarily affected by pyruvate kinase deficiency in terms of energy production?
Signup and view all the answers
Which enzyme is responsible for the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate?
Which enzyme is responsible for the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate?
Signup and view all the answers
What role does hexokinase play in glycolysis regulation?
What role does hexokinase play in glycolysis regulation?
Signup and view all the answers
What role does NAD+ play in the reaction converting glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate?
What role does NAD+ play in the reaction converting glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate?
Signup and view all the answers
How is glucokinase indirectly regulated in glycolysis?
How is glucokinase indirectly regulated in glycolysis?
Signup and view all the answers
In substrate level phosphorylation, what compound provides the energy to synthesize ATP?
In substrate level phosphorylation, what compound provides the energy to synthesize ATP?
Signup and view all the answers
What is the consequence of fluoride's presence in glycolysis?
What is the consequence of fluoride's presence in glycolysis?
Signup and view all the answers
What is the consequence of pyruvate kinase deficiency in RBCs?
What is the consequence of pyruvate kinase deficiency in RBCs?
Signup and view all the answers
How does 3-phosphoglycerate convert to 2-phosphoglycerate?
How does 3-phosphoglycerate convert to 2-phosphoglycerate?
Signup and view all the 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?
Signup and view all the answers
What type of reaction is catalyzed by pyruvate kinase?
What type of reaction is catalyzed by pyruvate kinase?
Signup and view all the answers
Which molecule is produced alongside ATP during the conversion of phosphoenol pyruvate to pyruvate?
Which molecule is produced alongside ATP during the conversion of phosphoenol pyruvate to pyruvate?
Signup and view all the answers
Which enzyme is responsible for the phosphorylation of glucose to glucose 6-phosphate?
Which enzyme is responsible for the phosphorylation of glucose to glucose 6-phosphate?
Signup and view all the answers
What is the primary function of isomerization in glycolysis?
What is the primary function of isomerization in glycolysis?
Signup and view all the answers
Which reaction in glycolysis is catalyzed by phosphofructokinase and is considered the key regulatory step?
Which reaction in glycolysis is catalyzed by phosphofructokinase and is considered the key regulatory step?
Signup and view all the answers
Which molecule is produced during the breakdown of fructose 1,6-bisphosphate?
Which molecule is produced during the breakdown of fructose 1,6-bisphosphate?
Signup and view all the answers
In which phase of glycolysis does the phosphorylation of fructose 6-phosphate occur?
In which phase of glycolysis does the phosphorylation of fructose 6-phosphate occur?
Signup and view all the answers
What is the result of substrate-level phosphorylation during glycolysis?
What is the result of substrate-level phosphorylation during glycolysis?
Signup and view all the answers
What effect does the phosphorylation of glucose have on its transport across the cell membrane?
What effect does the phosphorylation of glucose have on its transport across the cell membrane?
Signup and view all the answers
Which of the following tissues primarily relies on glycolysis for energy due to a lower presence of mitochondria?
Which of the following tissues primarily relies on glycolysis for energy due to a lower presence of mitochondria?
Signup and view all the answers
Study Notes
Isomerization
- Dihydroxyacetone phosphate is converted to glyceraldehyde 3-phosphate by phosphotriose isomerase.
- Two molecules of glyceraldehyde 3-phosphate are produced in this reversible reaction.
Oxidation
- Glyceraldehyde 3-phosphate undergoes dehydrogenation and phosphorylation to form 1,3-bisphosphoglycerate (1,3-BPG), catalyzed by glyceraldehyde 3-phosphate dehydrogenase (G3-P DH).
- NAD+ carries reducing equivalents, and the reaction is reversible.
- This step is critical for generating NADH + H+ and high-energy compound 1,3-BPG.
Substrate-Level Phosphorylation
- 1,3-BPG's energy is used to synthesize ATP and produce 3-phosphoglycerate via 3-phosphoglycerate kinase.
- This is an instance of substrate-level phosphorylation and is reversible.
- Arsenate inhibits this reaction.
Shift of Phosphoryl Group
- 3-phosphoglycerate is converted to 2-phosphoglycerate by phosphoglycerate mutase, involving a phosphate group shift from C3 to C2.
- This reaction is reversible.
Dehydration
- 2-phosphoglycerate is dehydrated to form phosphoenolpyruvate (PEP), a high-energy compound, catalyzed by enolase.
- This reversible reaction removes one water molecule and requires Mg++.
- Fluoride irreversibly inhibits enolase, halting glycolysis, which is why fluoride is used during blood sugar estimations.
Substrate-Level Phosphorylation
- PEP converts to pyruvate via pyruvate kinase, producing ATP through substrate-level phosphorylation.
- Pyruvate kinase is considered a key enzyme and this marks the third irreversible reaction in glycolysis.
2,3-Bisphosphoglycerate Shuttle
- In RBCs, 1,3-BPG is transformed into 2,3-bisphosphoglycerate (2,3-BPG) by bisphosphoglycerate mutase.
- 2,3-BPG is hydrolyzed to 3-phosphoglycerate by phosphatase, without generating ATP.
- 2,3-BPG lowers hemoglobin's oxygen affinity, facilitating oxygen delivery to tissues under hypoxia.
Pyruvate Kinase Deficiency
- This inherited disorder represents the most common enzyme defect in the glycolytic pathway.
- It results in reduced glycolysis rates in RBCs, causing an energy deficit and leading to hemolytic anemia due to the inability of RBCs to maintain their biconcave shape.
Regulation of Glycolysis
- Regulated through allosteric mechanisms, covalent modifications, and hormonal influences.
Allosteric Regulation
- Key glycolytic enzymes include hexokinase/glucokinase, phosphofructokinase, and pyruvate kinase.
- Hexokinase is inhibited by glucose 6-phosphate; glucokinase is inhibited by fructose-6-P and stimulated by glucose; pyruvate kinase is inhibited by high ATP and activated by fructose 1,6-bisphosphate.
Glycolysis Tissue Distribution
- Glycolysis is prominent in mature RBCs, contracting muscles (due to vessel occlusion), tissues with fewer mitochondria (kidney medulla, testicles, leukocytes), and in the brain and gastrointestinal tract.
Glycolysis Overview
- The glycolytic pathway breaks down glucose into two pyruvate molecules through a sequence of 10 reactions, divided into:
- Energy investment phase (Preparatory phase): first 5 steps
- Energy generation phase (Payoff phase): last 5 steps
Phosphorylation
- Glucose is activated by hexokinase or glucokinase to form glucose 6-phosphate, an irreversible reaction requiring ATP and Mg++.
- The impermeable glucose 6-phosphate traps glucose within the cell for energy production.
Isomerization
- Glucose 6-phosphate is isomerized to fructose 6-phosphate, undergoing a reversible rearrangement from aldose to ketose.
Second Phosphorylation
- Fructose 6-phosphate is phosphorylated to fructose 1,6-bisphosphate by phosphofructokinase (PFK), the key enzyme in glycolysis, using ATP.
- This reaction is the second irreversible step.
Breakdown of Fructose 1,6-bisphosphate
- The 6-carbon fructose 1,6-bisphosphate is split into two 3-carbon molecules: glyceraldehyde 3-phosphate and dihydroxyacetone phosphate, catalyzed by aldolase.
- This reaction is reversible.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the biochemical processes of isomerization and oxidation involving glyceraldehyde 3-phosphate. This quiz covers key reactions catalyzed by phosphotriose isomerase and glyceraldehyde 3-phosphate dehydrogenase. Test your knowledge of reversible reactions in metabolic pathways.
