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Comprehensive MCAT Checklist - Carbohydrate Metabolism

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1. What is the primary reason why digestive enzymes are specific to D-sugars?
Because of the chirality and 3D structure of the sugars






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2. Which of the following would you expect in the breakdown of a disaccharide?
Hydrolysis by a glycosidase






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3. A student is asked to explain the structural difference of fructose from glucose, galactose, and mannose. The student states:

I. Fructose is a ketose, while the others are aldoses.
II. Fructose has 8 stereoisomers, while the others have 16.
III. Fructose contains 5 carbon atoms, while the others contain 6.

Which of the following is incorrect?
III only






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4. Which step of glycolysis is irreversible and is the first step of intracellular metabolism?
Conversion of glucose to glucose-6-phosphate by hexokinase






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5. During anaerobic glycolysis (fermentation), pyruvate is converted to lactate in order to:
Regenerate NAD⁺ for glycolysis to continue






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6. The deficiency of phosphorylase kinase would most likely result in impaired:
Conversion of glycogen to glucose-1-phosphate






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7. A disease is identified by the deficiency of NADPH. Which process is most likely affected, and which metabolic pathways are most likely to be impaired?
The pentose phosphate pathway; fatty acid synthesis






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8. Which metabolic process is not likely to involve the direct use or production of carbohydrate derivatives?
Beta-oxidation of fatty acids






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9. Which of the following molecules is both an allosteric activator and an allosteric inhibitor of glycogen metabolism?
Glucose-6-phosphate






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10. Which hormone promotes the storage of glucose?
Insulin






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11. Which enzyme is responsible for the committed step of glycolysis?
Phosphofructokinase-1 (PFK-1)






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12. In gluconeogenesis, which molecule serves as the primary substrate for glucose synthesis in the liver during fasting?
Lactate






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13. The pentose phosphate pathway is primarily important for:
Producing NADPH and ribose-5-phosphate






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14. Which of the following best describes the Cori cycle?
The cycling of lactate from muscle to liver and glucose back to muscle






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15. Which regulatory mechanism primarily controls glycogen synthesis and breakdown?
Phosphorylation and dephosphorylation of key enzymes