23 Questions
What is the function of Phosphofructokinase-1 in glycolysis?
The first committed step in the catabolic pathway of glycolysis
Pyruvate kinase is activated by ATP.
False
What is the significance of the ATP/AMP ratio in the regulation of glycolysis?
The ATP/AMP ratio reflects the energy state of the cell.
The accumulation of lactic acid is reflected by inhibition of PFK-1 by _______________________ pH.
low
Match the following enzymes with their functions in glycolysis:
Phosphofructokinase-1 = First committed step in glycolysis Pyruvate kinase = Regulated by ATP and alanine
What is the effect of fructose 1,6-bisphosphate on pyruvate kinase?
Activates pyruvate kinase
Glycogen breakdown is regulated by PFK-1.
False
What is the function of AMP in the regulation of PFK-1?
AMP activates PFK-1.
What is the result of the binding of phosphate groups to the active sites of enzymes?
Lowers the activation energy
The phosphorylation of glucose is an essentially reversible reaction under physiological conditions.
False
What is the name of the enzyme that phosphorylates glucose in the first step of glycolysis?
Hexokinase
The conversion of glucose 6-phosphate to fructose 6-phosphate is catalyzed by the enzyme _______________.
Phosphohexose Isomerase
How many ATP are consumed for each molecule of glucose that passes through the preparatory phase of glycolysis?
2
The phosphorylation of glucose increases the specificity of the enzymatic reactions.
True
Match the following enzymes with their corresponding reactions in glycolysis:
Hexokinase = Phosphorylation of glucose Phosphohexose Isomerase = Conversion of glucose 6-phosphate to fructose 6-phosphate
What is the product of Step #10 in glycolysis?
Pyruvate
The standard free energy of hydrolysis of the phosphate groups of the reactant in Step #9 is -61.9 kJ/mol.
False
What is the name of the enzyme that transfers the high-energy phosphoryl group from the carboxyl group to ADP, forming ATP and 3-phosphoglycerate?
Phosphoglycerate kinase
In Step #8, 3-phosphoglycerate is converted to _______________________.
2-phosphoglycerate
Match the following compounds with their corresponding steps in glycolysis:
3-phosphoglycerate = Step #8 Phosphoenolpyruvate = Step #9 Pyruvate = Step #10
What is the result of the loss of the water molecule in Step #9?
Generation of a high-energy phosphate compound
The reaction in Step #10 is reversible.
False
What is the name of the form of pyruvate that is more stable at pH 7?
Keto form
Study Notes
Glycolysis: Preparatory Phase
- For each molecule of glucose that passes through the preparatory phase, two molecules of glyceraldehyde 3-phosphate are formed and two ATP are consumed.
Phosphorylation of Glucose
- Glucose is phosphorylated at C-6 to yield glucose 6-phosphate using ATP as the phosphoryl donor.
- This step is essentially irreversible under physiological conditions.
Conversion of Glucose 6-phosphate to Fructose 6-phosphate
- Phosphohexose isomerase catalyzes the reversible isomerization of glucose 6-phosphate (an aldose) to fructose 6-phosphate (a ketose).
Phosphofructokinase-1 (PFK-1)
- PFK-1 is the most important regulatory point and the first committed step in the catabolic pathway of glycolysis.
- The activity of PFK-1 increases when ATP is low.
Regulation of Phosphofructokinase
- PFK-1 is inhibited by ATP (allosteric inhibition) and activated by AMP (allosteric activation).
- PFK-1 is also inhibited by low pH, reflecting lactic acid accumulation due to anaerobic respiration.
Phosphoglycerate Kinase
- Phosphoglycerate kinase transfers the high-energy phosphoryl group from the carboxyl group to ADP, forming ATP and 3-phosphoglycerate.
Conversion of 3-Phosphoglycerate to 2-Phosphoglycerate
- 3-Phosphoglycerate is converted to 2-phosphoglycerate, involving a conformational change.
Dehydration of 2-Phosphoglycerate to Phosphoenolpyruvate
- 2-Phosphoglycerate is dehydrated to form phosphoenolpyruvate, generating a super high-energy phosphate compound.
Transfer of the Phosphoryl Group from PEP to ADP
- This step is also an important site of regulation and marks the end of glycolysis, producing pyruvate.
This quiz covers the binding of phosphate groups to enzymes, activation energy, and specificity of enzymatic reactions in the context of glycolysis.
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