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Questions and Answers
What is the primary purpose of glycolysis?
What is the primary purpose of glycolysis?
In which cellular compartment does glycolysis take place?
In which cellular compartment does glycolysis take place?
What is the net ATP yield from the anaerobic oxidation of one mole of glucose in glycolysis?
What is the net ATP yield from the anaerobic oxidation of one mole of glucose in glycolysis?
Which enzyme is responsible for converting glucose-6-phosphate into fructose-1,6-diphosphate?
Which enzyme is responsible for converting glucose-6-phosphate into fructose-1,6-diphosphate?
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Which tissues primarily rely on glycolysis due to their lack of mitochondria?
Which tissues primarily rely on glycolysis due to their lack of mitochondria?
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What is the primary purpose of fluorinating blood samples before measuring glucose levels?
What is the primary purpose of fluorinating blood samples before measuring glucose levels?
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How many ATP are utilized in the ATP-utilizing steps of glycolysis?
How many ATP are utilized in the ATP-utilizing steps of glycolysis?
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Which of the following is NOT a biological function of glycolysis?
Which of the following is NOT a biological function of glycolysis?
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What occurs when oxygen is not available during glycolysis?
What occurs when oxygen is not available during glycolysis?
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Which two substances are produced from one mole of glucose during glycolysis under aerobic conditions?
Which two substances are produced from one mole of glucose during glycolysis under aerobic conditions?
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What does an increase in 2,3-DPG levels indicate in the body?
What does an increase in 2,3-DPG levels indicate in the body?
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Why is blood stored in blood banks unsuitable for hypoxic patients after ten days?
Why is blood stored in blood banks unsuitable for hypoxic patients after ten days?
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Which pathway utilizes inosine to increase 2,3-DPG levels in red blood cells?
Which pathway utilizes inosine to increase 2,3-DPG levels in red blood cells?
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Under aerobic conditions, what is the total amount of ATP produced from one mole of glucose after considering the initial ATP loss?
Under aerobic conditions, what is the total amount of ATP produced from one mole of glucose after considering the initial ATP loss?
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What is the primary product of glucose conversion when oxygen is present?
What is the primary product of glucose conversion when oxygen is present?
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Which enzyme is considered the most important regulatory enzyme in glycolysis?
Which enzyme is considered the most important regulatory enzyme in glycolysis?
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What is the net ATP yield from anaerobic glycolysis?
What is the net ATP yield from anaerobic glycolysis?
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Which shuttle system is responsible for producing 5 ATP in the aerobic oxidation of glucose?
Which shuttle system is responsible for producing 5 ATP in the aerobic oxidation of glucose?
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What effect does insulin have on the key regulatory enzyme of glycolysis?
What effect does insulin have on the key regulatory enzyme of glycolysis?
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Which of the following substances can inhibit the enzyme hexokinase in glycolysis?
Which of the following substances can inhibit the enzyme hexokinase in glycolysis?
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What is the role of citrate in the regulation of glycolysis?
What is the role of citrate in the regulation of glycolysis?
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Which enzyme is primarily responsible for the conversion of glucose to glucose-6-phosphate in glycolysis?
Which enzyme is primarily responsible for the conversion of glucose to glucose-6-phosphate in glycolysis?
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What molecule is produced as a result of the action of phosphofructokinase?
What molecule is produced as a result of the action of phosphofructokinase?
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Which enzyme catalyzes the conversion of 3-phosphoglycerate to 2-phosphoglycerate?
Which enzyme catalyzes the conversion of 3-phosphoglycerate to 2-phosphoglycerate?
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What is the final product of the glycolytic pathway?
What is the final product of the glycolytic pathway?
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Which of the following molecules inhibits glyceraldehyde-3-phosphate dehydrogenase?
Which of the following molecules inhibits glyceraldehyde-3-phosphate dehydrogenase?
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Which substrate is necessary for aldolase to function in the glycolytic pathway?
Which substrate is necessary for aldolase to function in the glycolytic pathway?
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Which of the following enzymes catalyzes the conversion of 1,3-diphosphoglycerate to 3-phosphoglycerate?
Which of the following enzymes catalyzes the conversion of 1,3-diphosphoglycerate to 3-phosphoglycerate?
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Which cofactor is essential for the activity of phosphofructokinase?
Which cofactor is essential for the activity of phosphofructokinase?
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Which step in glycolysis involves the conversion of Glyceraldehyde-3-phosphate into 1,3-diphosphoglycerate?
Which step in glycolysis involves the conversion of Glyceraldehyde-3-phosphate into 1,3-diphosphoglycerate?
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Study Notes
Carbohydrate Metabolism
- Glycolysis is a cascade of reactions that converts glucose into two pyruvate molecules.
- It aims at producing ATP and other intermediates.
- It is also used in the opposite direction for gluconeogenesis.
- It occurs in the cytoplasm.
- Red blood cells (RBCs) rely on glycolysis as their primary energy source due to their lack of mitochondria.
- Contracting muscles use glycolysis as their main energy source during periods of low oxygen availability due to blood vessel occlusion during contraction.
- The cornea and lens also depend on glycolysis due to limited blood supply and lack of mitochondria.
- Glucose transport into cells is insulin-dependent in muscles and adipose tissue, but not in other vital tissues like the brain, heart, kidney, and red blood cells (RBCs).
- Liver cells are freely permeable to glucose, allowing its entry and exit.
Glycolysis Steps
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Two Phases:
- ATP-Utilizing Steps: Glucose is converted to 2 glyceraldehyde 3-phosphate, consuming 2 ATP.
- ATP-Producing Steps: 2 glyceraldehyde 3-phosphate is converted to 2 pyruvate in aerobic conditions or 2 lactate in anaerobic conditions. This generates a net gain of ATP.
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Key Enzymes (Glycolysis):
- Hexokinase (or glucokinase)
- Phosphofructokinase
- Pyruvate kinase
Glycolysis Regulation
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Key Regulatory Enzymes:
- Hexokinase or glucokinase
- Phosphofructokinase
- Pyruvate kinase
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Phosphofructokinase Regulation:
- Stimulated by: fructose-6-phosphate, fructose-2,6-diphosphate, ADP, and AMP.
- Inhibited by: ATP, low pH, and citrate.
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Hormonal Regulation:
- Insulin stimulates key regulatory enzymes for glycolysis.
- Adrenaline and glucagon inhibit these enzymes.
In Vitro Inhibition of Glycolysis
- 1-Deoxyglucose: Inhibits hexokinase and glucokinase.
- 2-Arsenate: Resembles inorganic phosphate and replaces phosphate in the reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase; this uncouples oxidation and phosphorylation (ATP synthesis).
- 3-Iodoacetate: A sulfhydryl (SH) poison that inhibits glyceraldehyde-3-phosphate dehydrogenase.
- 4-Fluoride: Inhibits enolase, so samples should be fluorinated to stop glycolysis in blood cells before blood glucose levels are tested.
Biological Importance of Glycolysis
- ATP formation
- Production of 2,3-DPG, important in tissue oxygenation.
- Reversal of glycolysis forms gluconeogenesis, an important source of glucose.
- Main pathway of fructose metabolism from the diet.
Rapoport-Lubering Cycle
- A shunt pathway from glycolysis.
- Aims at the formation of 2,3-Diphosphoglycerate (2,3-DPG).
- This cycle has two steps.
2,3-DPG Biochemical Significance
- Decreases the affinity of hemoglobin (Hb) to oxygen, aiding in oxygen release.
- Levels increase in hypoxic conditions (high altitudes, hypoxia, etc.).
- During blood storage in banks, 2,3-DPG concentration declines. This lowered level causes hemoglobin to bind oxygen tighter, making the blood unsuitable for hypoxic patients.
RBCs Membrane Permeability
- RBC membrane is impermeable to 2,3-DPG.
- Inosine is added instead to facilitate entry into red blood cells and proceed to DPG production via other pathways.
Other Key Information
- Aerobic Conditions (Energy Yield): Gain 7 or 9 ATP, depending on shuttle.
- Anaerobic Conditions (Energy Yield): Gain 2 ATP.
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Quiz Answers:
- Question 1: Pyruvate
- Question 2: 2
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Description
This quiz covers the fundamental processes of carbohydrate metabolism with a focus on glycolysis. Explore the key reactions, ATP production, and how glycolysis plays a crucial role in various tissues under different conditions. Perfect for students studying biochemistry or related fields.
