Multiple Choice
Dr. Kumar has discovered an enzyme that catalyzes the hydrolysis of lactose into glucose and galactose. What is the most appropriate name for this enzyme according to standard enzyme nomenclature?
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6. Enzymes and Enzyme Kinetics
Enzymes
Multiple Choice
Which of the following enzymes must all gluconeogenic tissues express in order to carry out gluconeogenesis?
A
Pyruvate kinase
B
Hexokinase
C
Phosphofructokinase-1 (PFK-1)
D
Glucose-6-phosphatase
Verified step by step guidance1
Step 1: Understand the process of gluconeogenesis. Gluconeogenesis is the metabolic pathway that generates glucose from non-carbohydrate precursors, such as lactate, glycerol, and amino acids. It primarily occurs in the liver and kidneys.
Step 2: Identify the enzymes involved in gluconeogenesis. Gluconeogenesis bypasses the irreversible steps of glycolysis by using specific enzymes. These include pyruvate carboxylase, phosphoenolpyruvate carboxykinase (PEPCK), fructose-1,6-bisphosphatase, and glucose-6-phosphatase.
Step 3: Recognize the role of glucose-6-phosphatase. This enzyme is essential for the final step of gluconeogenesis, where glucose-6-phosphate is converted into free glucose. This step is crucial for exporting glucose into the bloodstream, especially in the liver and kidneys.
Step 4: Compare the listed enzymes. Pyruvate kinase, hexokinase, and phosphofructokinase-1 (PFK-1) are glycolytic enzymes that function in glucose breakdown, not synthesis. These enzymes are not involved in gluconeogenesis and are not required for this pathway.
Step 5: Conclude that glucose-6-phosphatase is the correct answer. It is the enzyme that all gluconeogenic tissues must express to complete gluconeogenesis and release glucose into the bloodstream.
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