Question

Match each term with its description. (a) Hexokinase (b) Phosphoglucose isomerase (c) Phosphofructokinase (d) Aldolase (e) Triose phosphate isomerase (f) Glyceraldehyde 3-phosphate dehydro genase (g) Phosphoglycerate kinase (h) Phosphoglycerate mutase (i) Enolase (j) Pyruvate kinase 1\. Forms fructose \(1,6-\) bisphosphate 2\. Generates the first highphosphoryl-transferpotential compound that is not ATP 3\. Converts glucose 6 -phosphate into fructose 6 -phosphate 4\. Phosphorylates glucose 5\. Generates the second molecule of ATP 6\. Cleaves fructose \(1,6-\) bisphosphate 7\. Generates the second high-phosphoryltransfer-potential compound that is not ATP 8\. Catalyzes the interconversion of three-carbon isomers 9\. Converts 3-phosphoglycerate into 2 -phosphoglycerate 10\. Generates the first molecule of ATP

Short answer

4-a, 3-b, 1-c, 6-d, 8-e, 2-f, 10-g, 9-h, 7-i, 5-j

Step-by-step solution

Match Function Descriptions

Identify the description for each enzyme based on their biochemical roles in glycolysis.

Hexokinase

Hexokinase catalyzes the phosphorylation of glucose to form glucose 6-phosphate. Hence, it corresponds to the description: **4. Phosphorylates glucose**.

Phosphoglucose Isomerase

This enzyme converts glucose 6-phosphate into fructose 6-phosphate. So, it corresponds to the description: **3. Converts glucose 6-phosphate into fructose 6-phosphate**.

Phosphofructokinase

Phosphofructokinase catalyzes the formation of fructose 1,6-bisphosphate from fructose 6-phosphate, which corresponds to: **1. Forms fructose 1,6-bisphosphate**.

Aldolase

Aldolase cleaves fructose 1,6-bisphosphate into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate. It corresponds to: **6. Cleaves fructose 1,6-bisphosphate**.

Triose Phosphate Isomerase

This enzyme catalyzes the interconversion of glyceraldehyde 3-phosphate and dihydroxyacetone phosphate, matching the description: **8. Catalyzes the interconversion of three-carbon isomers**.

Glyceraldehyde 3-phosphate Dehydrogenase

This enzyme catalyzes the oxidation and phosphorylation of glyceraldehyde 3-phosphate to form 1,3-bisphosphoglycerate, which is the first high phosphoryl-transfer-potential compound. Thus, it corresponds to: **2. Generates the first high-phosphoryl-transfer-potential compound that is not ATP**.

Phosphoglycerate Kinase

Phosphoglycerate kinase catalyzes the transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP to form ATP and 3-phosphoglycerate, matching: **10. Generates the first molecule of ATP**.

Phosphoglycerate Mutase

This enzyme facilitates the conversion of 3-phosphoglycerate into 2-phosphoglycerate, corresponding to: **9. Converts 3-phosphoglycerate into 2-phosphoglycerate**.

Enolase

Enolase catalyzes the conversion of 2-phosphoglycerate into phosphoenolpyruvate, which is the second high phosphoryl-transfer-potential compound. Thus, it matches: **7. Generates the second high-phosphoryl-transfer-potential compound that is not ATP**.

Pyruvate Kinase

Pyruvate kinase transfers a phosphate from phosphoenolpyruvate to ADP to form ATP and pyruvate. Therefore, it corresponds to: **5. Generates the second molecule of ATP**.

Key concepts

Hexokinase

Hexokinase is one of the first enzymes involved in the glycolysis pathway, playing a critical role in the early stages of glucose metabolism. Its main function is to phosphorylate glucose, transforming it into glucose 6-phosphate. This is a crucial step because it essentially "traps" glucose within the cell, preventing it from exiting and allowing further metabolic processing.
This phosphorylation is important as it starts the process of glycolysis, leading glucose down a path where it will eventually be broken down for energy extraction. Hexokinase is regarded as a "pacemaker" of glycolysis, meaning it helps regulate the pace of the entire pathway by controlling the amount of glucose that enters the system.

Phosphofructokinase

Phosphofructokinase (PFK) is often referred to as the "committed step" of glycolysis, meaning once fructose 6-phosphate is created, it will be metabolized up to the pyruvate stage. PFK catalyzes the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate by adding a phosphate group from ATP.
This reaction is vital in regulating the glycolytic process and is influenced by several factors, including the ratios of ATP/ADP and AMP/ATP. In essence, high levels of ATP inhibit PFK, slowing glycolysis during periods of energy sufficiency. Conversely, increased levels of AMP can activate PFK, speeding up glycolysis to generate more ATP. Due to its regulatory properties, PFK is recognized as one of the key enzymes controlling the glycolytic flow.

Pyruvate Kinase

Pyruvate kinase is an enzyme found towards the end of the glycolysis pathway and plays a pivotal role in the conversion of phosphoenolpyruvate (PEP) to pyruvate, creating ATP in the process. Essentially, it transfers a phosphate group from PEP directly to ADP to form ATP and pyruvate, making it a significant step in the energy-harvesting phase of glycolysis.
Pyruvate kinase is regulated by several mechanisms, including allosteric regulation and covalent modification. Levels of fructose 1,6-bisphosphate can activate it, a phenomenon known as "feed-forward activation." This makes pyruvate kinase a finely tuned regulatory enzyme, ensuring energy production aligns with the cell's metabolic needs.

Enzymes in Glycolysis

Enzymes in glycolysis play crucial and distinct roles in ensuring that glucose is efficiently broken down into pyruvate, resulting in the release of energy stored in the form of ATP. Each enzyme facilitates a specific reaction, helping to transform substrates through a series of steps.

• Hexokinase – initiates the glycolytic process by phosphorylating glucose.
• Phosphofructokinase – key regulatory enzyme, determines the flow through glycolysis.
• Pyruvate kinase – finalizing the pathway, ensuring ATP is harvested.

Together, these enzymes not only support basic cellular respiration but also play critical roles in adjusting the flow of metabolites in response to cellular energy demands. Their sophistication in regulation ensures that glycolysis is a highly efficient and adaptable pathway, meeting the energy requirements of diverse cell types.