What Do You Know About Carbohydrates? Quiz
Carbohydrates are sugars that can be found in most of the foods we consume, and they play a major role in especially when it comes to brain function and energy. Even when one is on a diet, they can’t avoid carbohydrates. What do you know about Carbohydrates? Take up the quiz below and get find out now more about these important sugars.
Questions and Answers
- 1.
A healthy 34 year old male demonstrates normal blood glucose levels after 12-hours of fasting. Which of the following reactions contributes most to the observed finding?
- A.
Glycogen-Glucose-1-phosphate
- B.
Acetyl CoA-Palmitate
- C.
Oxaloacetate -phosphoenolpyruvate
- D.
Fructose 6-phosphate-Frutose 1.6-bisphosphate
- E.
Acetoacetyl Coa-3 Hydroxy-3-methylglutaryl CoA
Correct Answer
C. Oxaloacetate -phosphoenolpyruvateExplanation
During fasting, the body needs to maintain normal blood glucose levels to provide energy to the cells. The conversion of oxaloacetate to phosphoenolpyruvate is a key step in the gluconeogenesis pathway, which is the process by which the body produces glucose from non-carbohydrate sources, such as amino acids and glycerol. This reaction helps to replenish glucose levels and maintain normal blood glucose levels during fasting.Rate this question:
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- 2.
In certain metabolic conditions, hepatocytes increase the conversion of glucose to ribulose-5-phosphate. This conversion most likely supplements which of the following?
- A.
Energy production
- B.
Glycogen storage
- C.
Ketone body synthesis
- D.
Cholesterol synthesis
- E.
Protein degradation
- F.
Uric acid production
Correct Answer
D. Cholesterol synthesisExplanation
In certain metabolic conditions, hepatocytes increase the conversion of glucose to ribulose-5-phosphate. Ribulose-5-phosphate is an intermediate in the pentose phosphate pathway, which generates NADPH. NADPH is required for the synthesis of cholesterol. Therefore, the increased conversion of glucose to ribulose-5-phosphate most likely supplements cholesterol synthesis.Rate this question:
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- 3.
A 12 year-old male presents to your office complaining of poor exercise tolerance. He describes muscle cramps on physical activity, especially after intense straining. He also describes urine discoloration that happens after strenuous activities. Further testing reveals that exercise tolerance can be greatly improved in this patient if glucose solution is infused during exercise. Which of the following substrate flow pathway is most likely deficient in this patient?
- A.
A
- B.
B
- C.
C
- D.
D
- E.
E
Correct Answer
A. AExplanation
The correct answer is A. The patient's symptoms of muscle cramps and urine discoloration after strenuous activities suggest a deficiency in substrate flow pathway A. This pathway involves the breakdown of glucose to produce energy during exercise. The fact that exercise tolerance can be improved with glucose infusion further supports this deficiency.Rate this question:
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- 4.
A 30 year-old female is diagnosed with Hashimoto’s thyroiditis and subsequently started on thyroid-replacement therapy. Which of the following is true about thyroid hormones?
- A.
They act by activation of tyrosine kinase
- B.
They act primarily by activation of adenylyl cyclase
- C.
They have a nuclear receptor
- D.
They have a cytoplasmic receptor.
- E.
They act by increasing the activity of phosphlipase C
Correct Answer
C. They have a nuclear receptorExplanation
Thyroid hormones have a nuclear receptor. This means that once the thyroid hormones enter the cell, they bind to specific receptors located in the nucleus. This binding activates the receptor and allows it to bind to DNA, leading to changes in gene expression and protein synthesis. This ultimately affects various physiological processes in the body, such as metabolism, growth, and development.Rate this question:
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- 5.
A 3 month-old male is being evaluated for muscle hypotonia and feeding difficulties. Physical examination reveals hepatomegaly and severe cardiomegaly. Muscle biopsy shows polysaccharide accumulation within lysosomes. Which of the following enzymes is most likely deficient in this patient?
- A.
Glucose-6-phosphatase
- B.
Glycogen phosphorylase
- C.
Acid α-glucosidase
- D.
Debrancher enzyme
- E.
Galactokinase
- F.
Pyruvate kinase
Correct Answer
C. Acid α-glucosidaseExplanation
The patient in this scenario presents with muscle hypotonia, feeding difficulties, hepatomegaly, and severe cardiomegaly. These findings suggest a glycogen storage disease, specifically Pompe disease, which is characterized by a deficiency of the enzyme acid α-glucosidase. Acid α-glucosidase is responsible for breaking down glycogen into glucose within lysosomes. Without this enzyme, glycogen accumulates in the lysosomes, leading to the clinical manifestations seen in this patient. Glucose-6-phosphatase deficiency is associated with glycogen storage disease type I, while glycogen phosphorylase deficiency is associated with McArdle disease. Debrancher enzyme deficiency is associated with glycogen storage disease type III. Galactokinase deficiency is associated with galactokinase deficiency galactosemia, and pyruvate kinase deficiency is associated with pyruvate kinase deficiency hemolytic anemia.Rate this question:
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- 6.
Some transmembrane receptors employ Janus Kinase (JAK) to stimulate enzymes in the cytoplasm. Which of the following substances is most likely to utilize this pathway?
- A.
Insulin
- B.
Platelet-derived growth factor (PDGF)
- C.
Growth hormone
- D.
Atrial natriuretic peptide
- E.
Progesterone
- F.
Gamma- aminobutyric acid (GABA)
Correct Answer
C. Growth hormoneExplanation
Growth hormone is most likely to utilize the JAK pathway because it is a peptide hormone that activates JAK receptors on the cell surface. Once activated, JAK phosphorylates and activates downstream signaling molecules, leading to the stimulation of enzymes in the cytoplasm. Insulin, PDGF, atrial natriuretic peptide, progesterone, and GABA do not typically utilize the JAK pathway for signaling.Rate this question:
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- 7.
An agent that specifically blocks the interaction of inositol triphosphate with its intracellular receptor would most likely decrease the activity of:
- A.
Phospholipase C
- B.
Lipoxygenase
- C.
Protein kinase C
- D.
Phosphodiesterase
- E.
Adenylate cyclase
Correct Answer
C. Protein kinase CExplanation
An agent that specifically blocks the interaction of inositol triphosphate with its intracellular receptor would most likely decrease the activity of Protein kinase C. Inositol triphosphate (IP3) is an important second messenger involved in the activation of Protein kinase C (PKC). When IP3 binds to its intracellular receptor, it triggers the release of calcium ions from intracellular stores, which in turn activates PKC. Therefore, blocking the interaction between IP3 and its receptor would inhibit the activation of PKC, leading to a decrease in its activity.Rate this question:
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- 8.
A 44 yea-old homeless male develops confusion and ophthalomoplegia. Upon review of the medical record, you discover that he has been admitted to the hospital with alcohol intoxication several times before. Which of the following reaction is most likely impaired in this patient?
- A.
A
- B.
B
- C.
C
- D.
D
- E.
E
- F.
F
- G.
G
Correct Answer
B. BExplanation
The patient's history of alcohol intoxication and the symptoms of confusion and ophthalmoplegia suggest that he may have developed Wernicke encephalopathy. This condition is caused by thiamine (vitamin B1) deficiency, which is commonly seen in chronic alcoholics due to poor nutrition and impaired absorption. Thiamine is essential for glucose metabolism in the brain, and its deficiency can lead to neurological symptoms such as confusion and ophthalmoplegia. Therefore, the most likely impaired reaction in this patient is the reaction that requires thiamine, which is reaction B.Rate this question:
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- 9.
A 34-year-old female develops moderate hyperglycemia during her first pregnancy and is diagnosed with gestational diabetes mellitus. Her glycemic status improves markedly after delivery. She says that her mother and younger sister both have “high blood sugars” during pregnancy. If this patient’s gestational hyperglycemia is genetically predisposed, this patient is most likely to have decreased activity in which of the following enzymes?
- A.
Glucokinase
- B.
Phosphofrutokinase
- C.
Aldolase
- D.
Pyruvate kinase
- E.
Enolase
- F.
Pyruvate cardoxylase
- G.
Lactate dehydrogenase
Correct Answer
A. GlucokinaseExplanation
The correct answer is Glucokinase. Gestational diabetes mellitus (GDM) is a condition characterized by high blood sugar levels during pregnancy. In this case, the patient's mother and younger sister also had high blood sugars during pregnancy, suggesting a genetic predisposition. Glucokinase is an enzyme involved in glucose metabolism, specifically in the conversion of glucose to glucose-6-phosphate. Decreased activity of glucokinase would impair this conversion, leading to hyperglycemia. Therefore, if the patient's gestational hyperglycemia is genetically predisposed, she is most likely to have decreased activity in glucokinase.Rate this question:
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- 10.
A 64 year-old male hospitalized with severe abdominal pain and hypotension beings to hyperventilate. Laboratory testing reveals metabolic acidosis, an increased anion gap and high plasma lactate level. This patient’s findings are best explained by a low activity of:
- A.
Pyruvate kinase
- B.
Lactate Dehydrogenase
- C.
Pyruvate dehydrogenase
- D.
Pyruvate carboxylase
- E.
Enolase
Correct Answer
C. Pyruvate dehydrogenaseExplanation
Pyruvate dehydrogenase is responsible for converting pyruvate into acetyl-CoA, which is a crucial step in the citric acid cycle (also known as the Krebs cycle) that produces energy in the form of ATP. A deficiency in pyruvate dehydrogenase leads to an accumulation of pyruvate, which is then converted into lactate through lactate dehydrogenase. This results in metabolic acidosis, increased anion gap, and high plasma lactate levels, as seen in the patient's laboratory findings. Therefore, a low activity of pyruvate dehydrogenase best explains the patient's symptoms.Rate this question:
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- 11.
A 3 year-old male suffers from chronic diarrhea, greasy stool and anemia. This patient is significantly underweight. He has mild edema of the lower extremities and oral ulcers. Parenteral feeding and vitamin supplementation are started in this patient. Pantothenic acid is necessary for which of the following conversions in this patient’s metabolism?
- A.
Glucose to pyruvate
- B.
Glucose to ribose-5-phosphate
- C.
Alanine to glucose
- D.
Oxaloacetate to citrate
- E.
Glutamate to a ketoglutarate
Correct Answer
D. Oxaloacetate to citrateExplanation
Pantothenic acid is necessary for the conversion of oxaloacetate to citrate in this patient's metabolism. This patient is experiencing chronic diarrhea, greasy stool, anemia, significant underweight, mild edema of the lower extremities, and oral ulcers. These symptoms suggest a malabsorption disorder, which can lead to deficiencies in various nutrients, including pantothenic acid. Pantothenic acid is a component of coenzyme A, which is required for the conversion of oxaloacetate to citrate in the citric acid cycle. Therefore, supplementation of pantothenic acid is necessary to support this metabolic conversion in the patient.Rate this question:
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- 12.
A group of investigators studies the intracellular mechanisms of signal transduction. In a series of experiments, they demonstrate that pretreatment with tumor necrosis factor alpha (TNF-alpha) result in decrease insulin-mediated glucose uptake. TNF-alpha causes a defect in which of the following processes?
- A.
CAMP hydrolyzation
- B.
Phosphatidylinositol cleavage
- C.
Stimulation of peroxisome proliferator activated receptor
- D.
Serine residue phosphorylation
- E.
Proline residue hydroxylation
Correct Answer
D. Serine residue phosphorylationExplanation
The group of investigators found that pretreatment with tumor necrosis factor alpha (TNF-alpha) resulted in a decrease in insulin-mediated glucose uptake. This suggests that TNF-alpha causes a defect in serine residue phosphorylation, which is a crucial process in signal transduction. Serine residue phosphorylation plays a key role in the activation of various signaling pathways, including the insulin signaling pathway. Therefore, the decrease in insulin-mediated glucose uptake observed in the experiments is likely due to the impaired phosphorylation of serine residues caused by TNF-alpha.Rate this question:
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- 13.
A sample of liver parenchyma is homogenized and centrifuged to remove membrane components and organelles leaving only the cytosol and the proteins it contains. Which of the following enzyme activities is most likely present in the homogenate?
- A.
Pyruvate carboxylase
- B.
Ornithine transcarbmoylase
- C.
Transketolase
- D.
Succinate dehydrogenase
- E.
3-Hydroxy-3-merhylgutaryl-CoA lyase
Correct Answer
C. TransketolaseExplanation
The correct answer is Transketolase. Transketolase is an enzyme involved in the non-oxidative phase of the pentose phosphate pathway, which occurs in the cytosol. Since the sample only contains cytosol and the proteins it contains, it is likely that transketolase is present in the homogenate. The other enzymes listed are either located in other cellular compartments or are not directly involved in the cytosol.Rate this question:
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- 14.
Binding of GTP to a membrane-associated protein causes rapid metabolic changes in hepatocytes. These effects include a decrease in intracellular glycogen stores and the release of glucose into blood. Which of the following is the most likely mediator responsible for these effects?
- A.
CGMP-dependent protein kinase
- B.
Tyrosine-specific protein kinase
- C.
Protein kinase A
- D.
Phosphodiesterase
- E.
Janus tyrosine kinase (JAK)
Correct Answer
C. Protein kinase AExplanation
Binding of GTP to a membrane-associated protein is likely to activate Protein kinase A, which in turn causes rapid metabolic changes in hepatocytes. Protein kinase A is known to regulate glycogen metabolism through phosphorylation of key enzymes involved in glycogen synthesis and breakdown. Activation of Protein kinase A leads to the phosphorylation and activation of glycogen phosphorylase, resulting in the breakdown of glycogen into glucose. This glucose is then released into the blood, leading to the decrease in intracellular glycogen stores and the release of glucose into the bloodstream.Rate this question:
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- 15.
Monosaccharide delivered to the liver may have different rates of intracellular metabolism. Which of the following substance has the highest rate of metabolism in the glycolytic pathway?
- A.
Glucose-6-phosphate
- B.
Mannose-6-phosphate
- C.
Galactose 1-phosphate
- D.
Fructose 1-phosphate
- E.
Glucose 1-phosphate
Correct Answer
D. Fructose 1-phosphateExplanation
Fructose 1-phosphate has the highest rate of metabolism in the glycolytic pathway. This is because fructose 1-phosphate is converted into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate, which are key intermediates in glycolysis. These intermediates can then be further metabolized to produce ATP and other energy-rich molecules. Therefore, fructose 1-phosphate is quickly metabolized to generate energy in the liver.Rate this question:
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- 16.
Liver cells that demonstrate a high concentration of fructose 2,6-biphosphate have a low rate of which of the following conversions?
- A.
Glucose → glycogen
- B.
Acetyl CoA → fatty acids
- C.
Alanine → glucose
- D.
Pyruvate → oxaloacetate
- E.
α-Ketoglutarate → glutarnate
Correct Answer
C. Alanine → glucoseExplanation
Liver cells that have a high concentration of fructose 2,6-biphosphate have a low rate of the conversion of alanine to glucose. Fructose 2,6-biphosphate is an allosteric activator of the enzyme phosphofructokinase-1 (PFK-1), which is a key regulatory enzyme in glycolysis. When fructose 2,6-biphosphate levels are high, PFK-1 is activated, promoting glycolysis and inhibiting gluconeogenesis. Alanine is a gluconeogenic amino acid that can be converted to glucose through gluconeogenesis. Therefore, when fructose 2,6-biphosphate levels are high, the conversion of alanine to glucose is inhibited.Rate this question:
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- 17.
An infant who is apparently healthy at birth is diagnosed with aldolase B deficiency two weeks later. Which of the following should be removed from this patient’s diet?
- A.
Lactose
- B.
Sucrose
- C.
Maltose
- D.
Amylose
- E.
Cellulose
Correct Answer
B. SucroseExplanation
Aldolase B deficiency is a genetic disorder that affects the metabolism of fructose. Sucrose is a disaccharide made up of glucose and fructose, so if an infant with aldolase B deficiency consumes sucrose, their body will not be able to break it down properly. This can lead to a buildup of fructose and cause symptoms such as vomiting, lethargy, and failure to thrive. Therefore, sucrose should be removed from this patient's diet to prevent complications associated with aldolase B deficiency.Rate this question:
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- 18.
An infant born to 22 years-old female experiences lethargy, vomiting and jaundice soon after birth. The infant is places on a galactose - free formula and shows gradual improvement. Which of the following steps in galactose metabolism is most likely impaired in this patient?
- A.
A
- B.
B
- C.
C
- D.
D
- E.
E
Correct Answer
C. CExplanation
The most likely impaired step in galactose metabolism in this patient is step C. This is because the infant's symptoms of lethargy, vomiting, and jaundice are consistent with a condition called galactosemia, which is caused by a deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT). GALT is responsible for converting galactose-1-phosphate to glucose-1-phosphate, and its deficiency leads to the accumulation of galactose-1-phosphate in the body. By placing the infant on a galactose-free formula, the intake of galactose is eliminated, leading to gradual improvement in symptoms.Rate this question:
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- 19.
An apparently healthy 23 year-old male is found to excrete large amounts of fructose in his urine. Despite this patient’s defect in fructose metabolism, dietary fructose can still participate in glycogen synthesis in this patient due to the activity of:
- A.
Hexokinase
- B.
Fructokinse
- C.
Aldolase B
- D.
UDP-hexose 4-epimerase
- E.
Aldose reductase
Correct Answer
A. Hexokinase -
- 20.
A 78 year-old female suffers from nausea, anorexia, fatigue, and skin rash on her legs. She is mildly demented and is believed to have severe malnutrition. Laboratory findings include an organic aciduria. You suspect that biotin deficiency may contribute to this patient’s symptoms. Which of the following conversions is impaired in those with biotin deficiency?
- A.
Pyruvate to alanine
- B.
Pyruvate to oxaloacetate
- C.
Glucose to ribose-5-phosphate
- D.
Pyruvate to acetyl-CoA
- E.
Succinate to oxaloacetate
Correct Answer
B. Pyruvate to oxaloacetateExplanation
Biotin is a cofactor for the enzyme pyruvate carboxylase, which converts pyruvate to oxaloacetate. In biotin deficiency, the activity of pyruvate carboxylase is impaired, leading to a decreased conversion of pyruvate to oxaloacetate. This disruption in the conversion of pyruvate to oxaloacetate can contribute to the patient's symptoms of nausea, anorexia, fatigue, and skin rash on her legs, as well as the organic aciduria and severe malnutrition observed in this case.Rate this question:
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- 21.
An infant suffering from severe neurological symptoms and lactic acidosis with pyruvate dehydrogenase complex deficiency. When placed on a special diet, the patient demonstrates some decrease in the blood lactate level. Which of the following substances can be most safely supplemented to this patient?
- A.
Glycerol
- B.
Alanine
- C.
Galactose
- D.
Lysine
- E.
Asparagine
- F.
Serine
Correct Answer
D. LysineExplanation
Lysine can be safely supplemented to the patient because lysine is an essential amino acid that plays a crucial role in protein synthesis and energy production. In patients with pyruvate dehydrogenase complex deficiency, there is a disruption in the conversion of pyruvate to acetyl-CoA, leading to an accumulation of pyruvate and lactic acid. Lysine can help in the metabolism of pyruvate by serving as a precursor for acetyl-CoA, thus reducing the levels of lactate in the blood.Rate this question:
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- 22.
A 6 month-old male is brought to the ER with recent onset vomiting, irritability and jaundice. The infant was born at term and has been apparently healthy until the onset of these symptoms. All of his vaccinations are up-to-date. He has been exclusively breast-fed until one week ago when cereals and fruit juices were introduced into his diet. Further evaluation reveals hepatomegaly and abnormal liver function tests. Which of the following enzyme deficiencies is the most likely cause of this patient’s condition?
- A.
Galactose-1-phosphate uridyl transferase
- B.
Aldolase B
- C.
Fructokinase
- D.
Galactokinase
- E.
Acid α- glucosidase
Correct Answer
B. Aldolase BExplanation
The most likely cause of this patient's condition is Aldolase B deficiency. The patient's symptoms of vomiting, irritability, and jaundice, along with hepatomegaly and abnormal liver function tests, suggest a metabolic disorder affecting the liver. Aldolase B deficiency is an autosomal recessive disorder that leads to hereditary fructose intolerance. This condition presents with symptoms similar to those described in the patient, and the introduction of cereals and fruit juices into the diet may have triggered the symptoms due to the high fructose content in these foods.Rate this question:
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- 23.
A colony of cells is exposed to high-dose cortisol in an experimental setting. Which of the following intracellular substances is most likely to increase immediately after the exposure?
- A.
CAMP
- B.
IP3
- C.
Unbound hsp90
- D.
Activated Ras
- E.
Phosphorylated JAK
- F.
MRNA
Correct Answer
C. Unbound hsp90Explanation
In response to high-dose cortisol exposure, the cells may undergo a stress response. Hsp90 is a heat shock protein that plays a role in cellular stress response and acts as a chaperone for various proteins. When cells are exposed to stress, hsp90 can become unbound from its client proteins, allowing them to function independently. Therefore, it is likely that the level of unbound hsp90 will increase immediately after the exposure to high-dose cortisol.Rate this question:
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- 24.
Inhibition of lactate dehydrogenase in strenuously exercising skeletal muscles would eventually lead to an inhibition of Glycolysis due to intracellular depletion of which of the following substances?
- A.
AMP
- B.
FADH2
- C.
NAD
- D.
Carnitine
- E.
Pyruvate
- F.
Citrate
Correct Answer
C. NADExplanation
Inhibition of lactate dehydrogenase would lead to a decrease in the conversion of pyruvate to lactate, resulting in an accumulation of pyruvate. NAD is required for the conversion of pyruvate to acetyl-CoA, which is a key step in the Krebs cycle. Therefore, a depletion of NAD would inhibit the Krebs cycle and ultimately lead to an inhibition of glycolysis.Rate this question:
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- 25.
Activity of an enzyme called aldose reductase in the lens of a healthy individual produces sorbitol that can not exit the cells. Which of the following is the most likely product of sorbitol oxidation in these cells?
- A.
Glucose
- B.
Fructose
- C.
Galactose
- D.
Galactitol
- E.
Xylulose
Correct Answer
B. FructoseExplanation
The most likely product of sorbitol oxidation in these cells is fructose. This is because sorbitol can be converted to fructose through the action of the enzyme sorbitol dehydrogenase. Fructose is a common sugar found in many fruits and is an important source of energy for the body.Rate this question:
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.png "An infant born to 22 years-old female experiences lethargy, vomiting and jaundice soon after birth. The infant is places on a galactose - free formula and shows gradual improvement. Which of the following steps in galactose metabolism is most likely impaired in this patient?")
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Mar 20, 2023Quiz Edited by
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