Endo Carb Metab MCQ's
Carbohydrate metabolism begins in the mouth, where the enzyme salivary amylase begins to break down complex sugars into monosaccharide, which are later absorbed in the blood stream from the small intestine. Take this Endo carb meta MCQ`s below designed to assist you in passing the upcoming exam. All the best in the exam!
- 1.
A patient in your care is "addicted to cola". Most soft drinks are produced with HFCS 55 (approximately 55% Fructose and 45% glucose). What is one recommendation you should make to this patient regarding carbohydrate nutrition which derives from your knowledge of fructose metabolism?
- A.
Fructose is a bad sugar because it can cause fructose intolerance
- B.
Excessive dietary fructose is a leading cause of cataracts
- C.
Dietary fructose contributes to adipose tissue stores of triglycerides
- D.
Conversion of fructose to glucose requires no energy
- E.
The balance of sugars in colas are a benefit, but caffeine is bad
Correct Answer
C. Dietary fructose contributes to adipose tissue stores of triglyceridesExplanation
Excessive consumption of fructose, which is found in high amounts in soft drinks like cola, can contribute to the accumulation of triglycerides in adipose tissue. Triglycerides are a type of fat, and when they are stored in excess, it can lead to weight gain and an increased risk of obesity. Therefore, it is recommended for the patient to reduce their intake of dietary fructose, including cola, in order to prevent the storage of triglycerides in adipose tissue and maintain a healthy weight.Rate this question:
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- 2.
A patient who lacks all but 5% of the activity of the enzyme glycogen phosphorylase a will be expected to have a condition which has signs and symptoms most similar to another patient with a near total deficiency of which other enzyme/receptor?
- A.
The insulin receptor
- B.
The glycogen synthase b enzyme
- C.
The GLUT 4 transporter
- D.
The glycogen debranching enzyme
- E.
The fructose 2, 6-bisphosphatase enzyme
Correct Answer
D. The glycogen debranching enzymeExplanation
A patient who lacks all but 5% of the activity of the enzyme glycogen phosphorylase a will have a condition similar to another patient with a near total deficiency of the glycogen debranching enzyme. Both enzymes are involved in glycogen metabolism. Glycogen phosphorylase a breaks down glycogen into glucose-1-phosphate, while the glycogen debranching enzyme helps in the breakdown of glycogen by removing branch points. Therefore, a deficiency in either enzyme would result in impaired glycogen breakdown and similar signs and symptoms.Rate this question:
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- 3.
The term "reciprocal regulation" best describes the relationship between which two enzymes?
- A.
Glucose-6-phosphatase and Glucose6-phosphate dehydrogenase
- B.
Phosphofructokinase-1 and Pyruvate Kinase
- C.
Fructose-1,6-bisphosphatase and Pyruvate Carboxylase
- D.
Glycogen Synthase and Glycogen Phosphorylase
- E.
Fructokinase and Galactokinase
Correct Answer
D. Glycogen Synthase and Glycogen PhosphorylaseExplanation
Reciprocal regulation refers to a relationship where the activity of one enzyme is increased while the activity of the other enzyme is decreased, and vice versa. In the case of glycogen synthase and glycogen phosphorylase, they are both involved in the regulation of glycogen metabolism. Glycogen synthase adds glucose units to glycogen, while glycogen phosphorylase breaks down glycogen to release glucose. When glycogen phosphorylase is active and breaking down glycogen, glycogen synthase is inhibited. Conversely, when glycogen synthase is active and adding glucose units to glycogen, glycogen phosphorylase is inhibited. This reciprocal regulation ensures a balanced control of glycogen metabolism.Rate this question:
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- 4.
Which of the following is NOT an activity of insulin in maintenance of blood concentrations?
- A.
Increased adipose tissue GLUT 4 translocase concentration in the plasma membrane
- B.
Activation of glycogen synthase activity in liver
- C.
Activation of protein phosphatase-1 activity in liver
- D.
Activation of cAMP phosphodiesterase activity in liver
- E.
Activation of fructose1,6 bisphosphatase activity in liver
Correct Answer
E. Activation of fructose1,6 bisphosphatase activity in liverExplanation
Insulin is a hormone that plays a crucial role in regulating blood sugar levels. It helps to lower blood sugar by promoting the uptake of glucose into cells. The options given in the question are all activities of insulin except for the activation of fructose1,6 bisphosphatase activity in the liver. Fructose1,6 bisphosphatase is an enzyme involved in gluconeogenesis, the process of producing glucose from non-carbohydrate sources. Insulin actually inhibits the activity of fructose1,6 bisphosphatase, as it promotes glucose uptake and storage rather than glucose production. Therefore, the correct answer is the activation of fructose1,6 bisphosphatase activity in the liver.Rate this question:
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- 5.
Liver glucokinase activity is increased in the well-fed state. What is one reason for this change in activity as glucose concentrations rise?
- A.
Glucokinase has a Km in the physiological range of blood glucose
- B.
The Vmax of glucokinase is lower than that of hexokinase
- C.
The activity of the 'reverse' enzyme, glucose-6-phosphatase is stimulated by insulin
- D.
Hexokinase is subject to product inhibition
- E.
The reaction is endergonic, generating excess free energy
Correct Answer
A. Glucokinase has a Km in the physiological range of blood glucoseExplanation
Glucokinase has a Km in the physiological range of blood glucose, which means that it has a high affinity for glucose at normal blood glucose concentrations. As glucose concentrations rise in the well-fed state, the increased availability of glucose allows glucokinase to bind to and phosphorylate more glucose molecules, resulting in an increase in its activity. This is because the Km value represents the concentration of substrate needed for an enzyme to reach half of its maximum velocity (Vmax), so when glucose concentrations are within the physiological range, glucokinase is able to function optimally.Rate this question:
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- 6.
A patient in your care is producing most of his blood glucose from glycogen. Which clinical condition fits best with this finding?
- A.
The patient has not eaten solid food for 8 hours.
- B.
The patient has not eaten solid food for 12 days.
- C.
The patient has just had a big meal.
- D.
The patient has been on a corn starch and water diet.
- E.
The patient has been on a high protein, low carbohydrate diet.
Correct Answer
A. The patient has not eaten solid food for 8 hours.Explanation
The patient has not eaten solid food for 8 hours. During fasting, the body initially relies on glycogen stores in the liver to maintain blood glucose levels. After approximately 8-12 hours of fasting, glycogen stores become depleted, and the body starts to produce glucose through a process called gluconeogenesis. Therefore, the finding that the patient is producing most of his blood glucose from glycogen suggests that he has not eaten solid food for 8 hours.Rate this question:
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- 7.
A 45 y.o. patient is shown to have very poor exercise tolerance. After walking up a flight of stairs, the patient complains of muscle cramps and fatigue. A blood test is performed and shows that muscle protein is elevated (myoglobin). A muscle biopsy is performed and enzymatic analysis reveals that glucose is not responsive to changes in calcium concentration, but that the activity is otherwise similar to normal subjects. What enzyme deficiency is MOST LIKELY to explain these findings?
- A.
Hexokinase
- B.
Alanine aminotransferase
- C.
Phosphofructokinase-1
- D.
Phosphofructokinase-2
- E.
Glycogen Phosphorylase
Correct Answer
E. Glycogen PhosphorylaseExplanation
Glycogen Phosphorylase is the enzyme responsible for breaking down glycogen into glucose-1-phosphate, which can then be used as a source of energy. In this patient, the muscle biopsy revealed that glucose is not responsive to changes in calcium concentration, suggesting a deficiency in Glycogen Phosphorylase. This deficiency would impair the breakdown of glycogen, leading to a decrease in glucose availability for energy production during exercise, resulting in muscle cramps and fatigue.Rate this question:
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- 8.
It is the family July 4th picnic and Aunt Judy has forgotten her insulin injection. Her personal blood glucose monitoring device shows dangerously high glucose concentrations in her blood. Uncle Tommy comes to the rescue (he is also a diabetic) with his insulin kit, and Aunt Judy recovers except for the embarrassment she suffers from becoming drenched in perspiration in front of her entire extended family. How does insulin help to normalize her blood glucose levels?
- A.
Insulin stimulates glycogen synthase and phosphofructokinase-1
- B.
Insulin inhibits hexokinase and GLUT 4 transport of glucose
- C.
Insulin stimulates Glycogen Synthase Kinase-3 activity
- D.
Insulin stimulates bypass enzymes of gluconeogenesis
- E.
Insulin inhibits the activity of Pyruvate Kinase
Correct Answer
A. Insulin stimulates glycogen synthase and phosphofructokinase-1Explanation
Insulin stimulates glycogen synthase and phosphofructokinase-1, which are enzymes involved in the storage and breakdown of glucose. Glycogen synthase helps convert glucose into glycogen for storage in the liver and muscles, while phosphofructokinase-1 is involved in the breakdown of glucose for energy production. By stimulating these enzymes, insulin helps to lower blood glucose levels by promoting the storage of glucose as glycogen and inhibiting its breakdown for energy.Rate this question:
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- 9.
The appearance of ketone bodies in the urine is well documented in patients with uncontrolled type I diabetes. Acetoacetate can also be found in increased amounts in the urine in which of the following conditions?
- A.
High carbohydrate to fat ratio in the diet
- B.
High fat, low carbohydrate diet
- C.
Increased activity of HMG-CoA synthase in the fed state
- D.
In patients with carnitine deficiency
- E.
When omega oxidation of fatty acids is increased
Correct Answer
B. High fat, low carbohydrate dietExplanation
The appearance of ketone bodies in the urine is well documented in patients with uncontrolled type I diabetes. This is because in the absence of insulin, glucose cannot enter cells to be used as energy, so the body starts breaking down fats for energy instead. This leads to the production of ketone bodies, including acetoacetate, which are excreted in the urine. A high fat, low carbohydrate diet can also result in increased production of ketone bodies because the body is not getting enough carbohydrates to use as energy, so it turns to breaking down fats instead. This is known as nutritional ketosis.Rate this question:
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- 10.
In a patient with an insulinoma, you determine high background insulin levels are maintained well beyond 2 hours after the last meal. The high insulin levels will have what effects on the metabolism of glucose in the patient's liver?
- A.
Glycolysis and ATP generation will be limited
- B.
Gluconeogenesis will be activated
- C.
Glycogen synthase will be inhibited by GSK-3
- D.
Glycogen phosphorylase will be inhibited by Protein Phosphatase-1
- E.
ATP levels will allosterically activate Glycogen synthase
Correct Answer
D. Glycogen phosphorylase will be inhibited by Protein Phosphatase-1Explanation
The high insulin levels in a patient with an insulinoma will inhibit the activity of protein phosphatase-1, which in turn will inhibit glycogen phosphorylase. Glycogen phosphorylase is responsible for breaking down glycogen into glucose in the liver. Therefore, the inhibition of glycogen phosphorylase will result in decreased glucose production from glycogen, limiting glycolysis and ATP generation. This is consistent with the statement "Glycolysis and ATP generation will be limited."Rate this question:
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- 11.
An elderly patient in your care complains of dizziness. The patient is known to have a history of alcohol abuse. An oral glucose tolerance test (100 g glucose, blood glucose analyzed every 10 minutes thereafter) is performed and glucose is absorbed from the blood stream at a normal rate. Glucose is found to be out of the normal range (low) for the patient after a 6 hour fast, and free fatty acid levels are very low. One possible reason for the low glucose measurement
- A.
The patient has limited need for glucose at her advanced age.
- B.
The patient has a blood infection stimulated by a lack of nutrition
- C.
The circulating fatty acids are insufficient to drive liver gluconeogenesis.
- D.
Insulin release from the pancreas is limiting.
- E.
Metabolism of alcohol competitively inhibits enzymes for gluconeogenesis
Correct Answer
C. The circulating fatty acids are insufficient to drive liver gluconeogenesis.Explanation
The low glucose measurement in the patient could be due to the insufficient circulating fatty acids. Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate sources, such as fatty acids, in the liver. In this case, the patient's free fatty acid levels are very low, which means that there is a lack of substrates for gluconeogenesis. As a result, the liver is unable to produce enough glucose, leading to the low glucose measurement. This could be a consequence of the patient's history of alcohol abuse, as alcohol metabolism competes with gluconeogenesis enzymes and may deplete the supply of fatty acids available for glucose synthesis.Rate this question:
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- 12.
What is the most likely presenting symptom for a patient with a partial deficiency of an enzyme of the glycolytic pathway (glycolysis)?
- A.
Jaundice
- B.
Anemia
- C.
Sore throat
- D.
Intestinal discomfort
- E.
Rash
Correct Answer
B. AnemiaExplanation
A partial deficiency of an enzyme in the glycolytic pathway can lead to impaired energy production in red blood cells, resulting in a decreased number of healthy red blood cells and ultimately causing anemia. This is because glycolysis is an essential metabolic pathway for red blood cells to generate energy. Therefore, anemia is the most likely presenting symptom for a patient with this deficiency.Rate this question:
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- 13.
Analysis of enzymes activity before and after glucagon treatment is analyzed in a hepatic (liver) cell culture system. The following results are obtained, but the hospital administrator spilled coffee on the results: Enzyme Activity Assessed Before glucagon After glucagon Citrate Synthase 10 10 Enolase 10 10 Phosphoglucomutase 10 10 (obscured by coffee stain) 5 90 What could be a possible enzyme responsible for the given results.
- A.
PFK-1
- B.
Pyruvate Kinase
- C.
Isocitrate Dehydrogenase
- D.
Glucose 6-phosphate dehydrogenase
- E.
Glycogen Phosphorylase•
Correct Answer
E. Glycogen Phosphorylase•Explanation
The possible enzyme responsible for the given results is Glycogen Phosphorylase. This is because the activity of this enzyme is significantly increased after glucagon treatment, as indicated by the obscured result of 90. The other enzymes, Citrate Synthase, Enolase, and Phosphoglucomutase, show no significant change in activity before and after glucagon treatment, as their results remain the same at 10. Therefore, Glycogen Phosphorylase is the most likely enzyme responsible for the observed increase in activity after glucagon treatment.Rate this question:
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- 14.
While attending a meeting on childhood genetic disorders you overhear a discussion concerning a 6-month old infant presenting with cardiomegaly, hepatomegaly, feeding difficulties and generalized muscle weakness. The discussion is focused on the genetic disorder called "Infantile-onset Type II GSD" and "POMPE's GSD". What is the underlying cause of the infants symptoms?
- A.
Oxidative damage to erythrocytes
- B.
High levels of intracellular galactose 1-phosphate in liver
- C.
Hyperlacticacidemia
- D.
Accumulation of glycogen in lysosomes
- E.
Hypoglycemia
Correct Answer
D. Accumulation of glycogen in lysosomesExplanation
The infant's symptoms are consistent with the genetic disorder called "POMPE's GSD" or Infantile-onset Type II GSD. This disorder is characterized by the accumulation of glycogen in lysosomes, leading to cardiomegaly, hepatomegaly, feeding difficulties, and generalized muscle weakness. This accumulation of glycogen in lysosomes is the underlying cause of the infant's symptoms.Rate this question:
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- 15.
Inhibition of which enzyme activity will simultaneously shut down liver glycogenolysis and liver gluconeogenesis?
- A.
Glycogen phosphorylase 'a'
- B.
Pyruvate carboxylase
- C.
Glucose-6-phosphate dehydrogenase
- D.
Glucose-6-phosphatase
- E.
Phosphoglucose isomerase
Correct Answer
D. Glucose-6-phosphataseExplanation
Glucose-6-phosphatase is the correct answer because it is the enzyme responsible for the final step in both liver glycogenolysis and liver gluconeogenesis. It converts glucose-6-phosphate into glucose, which can then be released into the bloodstream. By inhibiting the activity of glucose-6-phosphatase, both processes will be shut down simultaneously.Rate this question:
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- 16.
A fructose only diet is close to that of the many "fruititarians" who practice eating only fruits in California, and elsewhere. How would you explain to such a person their condition of chronic fatigue?
- A.
Ascorbate causes problems with myosin-actin
- B.
Excess fructose depletes inorganic phosphate
- C.
Excess free fructose inhibits GLUT transport
- D.
Excess free fructose inhibits hexokinase and glucokinase
- E.
Fructose cannot be used to make energy*
Correct Answer
B. Excess fructose depletes inorganic phosphateExplanation
Excess fructose depletes inorganic phosphate, which is an essential component for energy production in the body. Without an adequate supply of inorganic phosphate, the body's ability to generate energy is compromised, leading to chronic fatigue. This is why someone following a fructose-only diet, like fruititarians, may experience chronic fatigue as a result of the depletion of inorganic phosphate caused by excess fructose consumption.Rate this question:
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- 17.
What is one difference between Aldolase A and Aldolase B which has clinical implications?
- A.
Aldolase A is found in the mitochondria, while Aldolase B is not
- B.
Aldolase A is involved in carbohydrate metabolism, and Aldolase B is not
- C.
Aldolase A is "fast" and Aldolase B is not
- D.
Aldolase A is found in liver tissue and Aldolase B is not
- E.
Aldolase A is dependent on thiamine-PP and Aldolase B is not
Correct Answer
C. Aldolase A is "fast" and Aldolase B is notExplanation
Aldolase A being "fast" and Aldolase B not being fast implies that Aldolase A has a higher catalytic efficiency or activity compared to Aldolase B. This difference in enzymatic activity can have clinical implications as it may affect the rate of carbohydrate metabolism and energy production in cells. It could potentially impact the overall metabolic function and health of an individual.Rate this question:
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- 18.
In the regulation of glycogen metabolism of a patient with Von Gierke Disease (deficiency of glucose-6-phosphatase deficiency), what is the expectation for the activity of glycogen synthase compared to a normal patient?
- A.
The "a" form of the enzyme will be activated to break down glycogen
- B.
The "b" form of the enzyme will be inactivated to produce less glycogen
- C.
The "a" form of the enzyme will be less active and glycogen will accumulate
- D.
There will be no change in enzyme activity in the patient
- E.
The "b" form of the enzyme will be allosterically activated
Correct Answer
E. The "b" form of the enzyme will be allosterically activatedExplanation
In Von Gierke Disease, there is a deficiency of glucose-6-phosphatase, which is required for the breakdown of glycogen. As a result, glycogen cannot be broken down properly and accumulates in the body. The "b" form of glycogen synthase is responsible for the production of glycogen. In this disease, the "b" form of the enzyme will be allosterically activated, meaning it will be more active than normal. This increased activity of glycogen synthase will lead to the production of more glycogen, further contributing to its accumulation in the patient.Rate this question:
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- 19.
The primary source of energy (ATP) under conditions of oxygen limitation in tissues is?
- A.
The Alanine Cycle
- B.
The Kreb’s Cycle (TCA)
- C.
Oxidative Phosphorylation
- D.
Glycolysis
- E.
The Cori Cycle
Correct Answer
D. GlycolysisExplanation
Anaerobic glycolysis produces 2 ATP per glucose metabolized. Lactate is the product formed from pyruvate to allow cycling of NAD+.Rate this question:
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- 20.
The most important allosteric regulator of glycolysis is fructose 1,6-bisphosphate?
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Fructose 2,6 bisphosphate controls PFK-1 activity (activates) allosterically. It also regulates Fructose 1, 6 bisphosphatase by comp. inhibition. (Fructose 1,6-bisphosphate is a glycolytic intermediate, not an enzyme effector).Rate this question:
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- 21.
Gluconeogenesis is most important?
- A.
After exercise
- B.
After meals
- C.
After prolonged fasting
- D.
Between lunch and dinner.
- E.
With anaerobic conditions
Correct Answer
C. After prolonged fastingExplanation
Overnight fasting releases glucagon in amounts which stimulate glycogenolysis. Prolonged fasting and depletion of glycogen stores results in activation of gluconeogenesis.Rate this question:
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- 22.
An important allosteric regulator of gluconeogenesis is fatty-acyl-CoA?
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Fatty-acyl-CoA’s are substrates for beta oxidation in mitochondria (catabolism). Acetyl-CoA is a 2 carbon substrate attached to CoA which serves as the allosteric effector of pyruvate carboxylase.Rate this question:
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- 23.
Number of hepatic translocases and/or enzymes which could be responsible for an observed failure of a patient to convert cytosolic glucose-6-phosphate into intracellular free glucose?
- A.
1
- B.
2
- C.
3
- D.
4
- E.
5
Correct Answer
E. 5Explanation
At least five ‘proteins or enzymes’, many more genes are involved because some of the translocases are multi-subunit, derived from multiple genes.Rate this question:
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- 24.
High free fatty acids are a hallmark of metabolic syndrome, a common precondition of Type II diabetes. High circulating fatty acids chronically cause modified phosphorylation on the intracellular domain of the insulin receptor, with reduced PI3K and reduced GLUT4 activity. How is low GLUT4 activity relevant to diabetes?
- A.
It causes retinopathy
- B.
It prevents glucose utilization by cells
- C.
It stimulates fructose uptake by cells
- D.
It leads to hyper-stimulation of glycolysis
- E.
It leads to a common foot infection
Correct Answer
B. It prevents glucose utilization by cellsExplanation
GLUT translocases have primary responsibility for glucose transport in liver. There are other glucose translocases, not influenced by insulin under normal circumstances.Rate this question:
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- 25.
Ischemic tissues have an increased rate of glycolysis. Most of this is not fueled by extracellular supply of glucose, but rather by locally stored glycogen that is degraded in response to ischemia. This response depends on the activation of glycogen phosphorylase by:
- A.
ATP
- B.
AMP
- C.
Low pH
- D.
Carbon Dioxide
- E.
Glucose 6-phosphate
Correct Answer
B. AMPExplanation
AMP activates the activity of glycogen phosphorylase in muscle tissues. Divalent calcium is also a similar allosteric effector of glycogen phosphorylase in liver.Rate this question:
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- 26.
Several inborn errors of carbohydrate metabolism can cause fasting hypoglycemia. The most severe fasting hypoglycemia has to be expected in deficiencies of:
- A.
Phosphofructokinase
- B.
Aldolase
- C.
Glycogen phosphorylase
- D.
Fructose-1,6-bisphosphatase
- E.
Glucose-6-phosphatase
Correct Answer
E. Glucose-6-phosphataseExplanation
Both gluconeogenesis and glycogenolysis result in formation of glucose-6-phosphate which can be converted to free glucose by only one enzyme found in liver: Glucose-6-phosphatase.Rate this question:
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Mar 20, 2023Quiz Edited by
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Feb 14, 2012Quiz Created by
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