PATHOLOGY OF CARBOHYDRATE METABOLISM

1. Indicate whether each of the following is true or false:

1) Insulin increases the intracellular concentration of glucose in hepatocytes

2) Glucagon is secreted in response to low blood glucose levels

3) Insulin increases the capacity of the liver to synthesize glycogen

4) Insulin has effects opposite to those of epinephrine and glucagon

5) Insulin, epinephrine, and glucagon all activate adenylate cyclase

6) Insulin activates phospholipase C

7) Glucagon increases triacylglycerol synthesis

8) Glycogen phosphorylase catalyzes glycogen breakdown in the absence of glucagon

A. True

B. False

 

2. Untreated diabetics experience hyperglycemia, which is an excess of glucose in their blood. Any glucose present in the blood normally gets reabsorbed by transporters present in the nephrons of the kidney. In diabetics not all blood glucose is reabsorbed and excreted in the urine. What is the most likely molecular explanation for this effect?

A. The transporters are inhibited by the presence of high levels of glucose

B. The binding affinity of these transporters is increased in diabetics

C. The Vmax of the transporter is reached at lower blood glucose levels

D. The binding capacity of the transporters has been exceeded

E. C and D

 

3. A two-year old boy was brought into the emergency room, suffering from severe fasting hypoglycemia. On physical examination, he was found to have hepatomegaly. Laboratory tests indicated that he also had lactic acidosis and hyperuricemia. A liver biopsy indicated that hepatocytes contained greater than normal amounts of glycogen that was of normal structure. The child was subsequently found to be missing which of the following enzymes?

A. Glycogen synthase

B. Glycogen phosphorylase

C. Glucose 6-phosphatase

D. Amylo-α(1→6)-glucosidase

E. Phosphoglucomutase

 

4. Following the intravenous injection of lactose into a rat, none of the lactose is metabolized. However, ingestion of lactose leads to rapid metabolism of this disaccharide. The difference in these observations is a result of:

A. The presence of lactase in the serum

B. The absence of hepatic galactokinase

C. The absence of maltase in the serum

D. The presence of lactase in the in the intestine

 

5. A galactosemic female is able to produce lactose because:

A. Free galactose is the acceptor of glucose transferred by lactose synthase in the synthesis of lactose

B. Galactose can be produced from a glucose metabolite by epimerization

C. Hexokinase can efficiently phosphorylate dietary galactose to galactose 1-phosphate

D. The enzyme deficient in galactosemia is activated by vasopressin.

E. Galactose can be produced from fructose by isomerization

 

6. Which tissues normally metabolize galactose?

A. Liver

B. Kidney

C. Intestine

D. Brain

E. All of the above

 

7. Which tissues normally metabolize fructose?

A. Liver

B. Kidney

C. Intestine

D. All of the above

 

8. Absolute insulin deficiency results in:

A. Insulinoma

B. Diabetes mellitus type 1

C. Diabetes mellitus type 2

D. Diabetes insipidus

E. None of the listed

 

9. Relative insulin deficiency results in:

A. Insulinoma

B. Diabetes mellitus type 1

C. Diabetes mellitus type 2

D. Diabetes insipidus

E. None of the listed

 

10. What is the common symptom of diabetes mellitus and diabetes insipidus?

A. Glucosuria

B. Polyuria

C. Polyphagia

D. Weight loss

E. All of the above

 

11. Relative or absolute lack of insulin in humans would result in which one of the following reactions in the liver?

A. Increased glycogen synthesis

B. Decreased gluconeogenesis from lactate

C. Decreased glycogenolysis

D. Increased formation of 3-hydroxybutyrate

E. Decreased action of hormone-sensitive lipase

 

12. Which of the following is most often found in untreated patients with Type 1 and Type 2 diabetes?

A. Hyperglycemia

B. Ketoacidosis

C. Extremely low levels of insulin synthesis and secretion

D. Obesity

E. A simple pattern of genetic inheritance

 

 

13. An obese individual with Type 2 diabetes:

A. Usually shows a normal glucose tolerance test

B. Usually has a lower plasma level of insulin than a normal individual

C. Usually shows significant improvement in glucose tolerance if body weight is reduced to normal

D. Usually has lower plasma levels of glucagon than a normal individual.

E. Usually is underweight

 

14. An individual with insulin resistance:

A. Usually shows elevated fasting glucose levels

B. Usually shows elevated fasting insulin levels

C. Will eventually become diabetic

D. Is rarely obese

E. Is treated by injection of insulin

 

15. Hereditary fructose intolerance is caused by deficiency in:

A. Glucokinase

B. Fructokinase

C. Galactokinase

D. Aldolase A

E. Aldolase B

 

16. Essential fructosuria is caused by deficiency in:

A. Glucokinase

B. Fructokinase

C. Galactokinase

D. Aldolase A

E. Aldolase B

 

17. Galactosemia type 1 is caused by deficiency in:

A. Galactokinase

B. Galactose 1-phosphate uridyltransferase

C. Epimerase

D. Aldolase A

E. Aldolase B

 

 

18. Galactosemia type 2 is caused by deficiency in:

A. Galactokinase

B. Galactose 1-phosphate uridyltransferase

C. Epimerase

D. Aldolase A

E. Aldolase B

 

19. Galactosemia type 3 is caused by deficiency in:

A. Galactokinase

B. Galactose 1-phosphate uridyltransferase

C. Epimerase

D. Aldolase A

E. Aldolase B

 

20. Lactose intolerance is caused by deficiency in:

A. Galactokinase

B. Galactose 1-phosphate uridyltransferase

C. Lactase

D. Aldolase A

E. Aldolase B

 

21. A patient with type 1 diabetes mellitus takes an insulin injection before eating dinner but then gets distracted and does not eat. Approximately 3 hours later, the patient becomes shaky, sweaty, and confused. These symptoms have occurred because of which of the following?

A. Increased glucagon release from the pancreas

B. Decreased glucagon release from the pancreas

C. High blood glucose levels

D. Low blood glucose levels

E. Elevated ketone body level

 

22. Which of the following organs has the highest demand for glucose as fuel?

A. Brain

B. Muscle

C. Heart

D. Liver

E. Pancreas

23. Glucagon release does not alter muscle metabolism because of which of the following?

A. Muscle cells lack adenylate cyclase

B. Muscle cells lack protein kinase A

C. Muscle cells lack G-proteins

D. Muscle cells lack GTP

E. Muscle cells lack glucagon receptor

 

24. An alcoholic patient developed pancreatitis that affected his exocrine pancreatic function. He exhibited discomfort after eating a high-carbohydrate meal. The patient most likely had a reduced ability to digest which of the following?

A. Starch

B. Lactose

C. Fiber

D. Sucrose

E. Maltose

 

25. A type 1 diabetic neglects to take his insulin injections while on a weekend vacation. Cells of which tissue will be most greatly affected by this mistake?

A. Brain

B. Liver

C. Muscle

D. Erythrocytes

E. Pancreas