GI Lipid Metab & Membrane Lipids MCQ's

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1. During starvation ketone bodies are synthesized in one of the following organs:

Explanation

During starvation, the body undergoes a process called ketogenesis, where ketone bodies are synthesized as an alternative fuel source. The liver plays a crucial role in this process as it is responsible for the production of ketone bodies. The liver breaks down fatty acids into ketone bodies, such as acetoacetate and beta-hydroxybutyrate, which can be used by various tissues, including the brain and muscles, for energy. Therefore, the liver is the organ where ketone bodies are synthesized during starvation.

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Lipids Quizzes & Trivia

A membrane lipid is a compound, which belongs to a group of which form the double-layered surfaces of all cells. Lipid metabolism is the synthesis and degradation of... see morelipids in cells where fat are broken down for energy. Take up the gi lipid metab & membrane lipids MCQ's below to see how well you understood the course. see less

2. Which of the following phospholipids induces hypersensitivity, triggers thrombotic events and causes alveolar macrophages to generate superoxide radicals?

Explanation

Platelet activating factor (PAF)
Hormone released from phagocytic cells binds to surface receptors
Causes platelets to aggregate and degranulate. It binds to surface receptors resulting in thrombotic and inflammatory events and anaphylactic reactions
Causes neutrophils and alveoli macrophages to produce superoxide radicals (useful for killing bacteria) (slide 18 Memb Lip-Laville)

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3. The site of action of the nonsteroidal anti-inflammatory drugs is:

Explanation

think COX

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4. A 29-year-old male decides to go on the Atkins diet. After approximately a month on the diet he complains of having what he describes as bad breath. What would be the biochemical findings in this patient?

Explanation

When following the Atkins diet, the body enters a state of ketosis where it relies on fat for energy instead of carbohydrates. This leads to increased beta-oxidation, the process by which fatty acids are broken down to produce energy. As a result, there is an increase in the production of ketone bodies, which are byproducts of fat metabolism. One of the symptoms of ketosis is bad breath, known as "ketone breath." Therefore, the biochemical findings in this patient would be increased beta-oxidation with subsequent increase in ketone bodies in the plasma, explaining the symptom of bad breath.

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5. A 5-year old female is presented with hepatosplenomegaly, abnormal bleeding disorders, defects in long bone development and neurological dysfunction. Laboratory analysis of a liver biopsy reveals that the patient has only 30 % activity of the enzyme glucoceribrosidase. This patient most likely is suffering from one of the following diseases:

Explanation

Symptoms may include enlarged spleen and liver, liver malfunction, skeletal disorders and bone lesions that may be painful, severe neurologic complications, swelling of lymph nodes and (occasionally) adjacent joints, distended abdomen, a brownish tint to the skin, anemia, low platelets and yellow fatty deposits on the sclera. Persons affected most seriously may also be more susceptible to infection. Some forms of Gaucher's disease may be treated with enzyme replacement therapy.
Gaucher's disease is a genetic disease in which lipids accumulates in cells and certain organs. Gaucher's disease is the most common of the lysosomal storage diseases. It is characterized by bruising, fatigue, anemia, low platelets, and enlargement of the liver and spleen. It is caused by a hereditary deficiency of the enzyme glucosylceramidase. The enzyme acts on the fatty acid glucosylceramide. When the enzyme is defective, glucosylceramide accumulates, particularly in white blood cells, most often macrophages (mononuclear leukocytes). Glucosylceramidase can collect in the spleen, liver, kidneys, lungs, brain and bone marrow.

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6. A patient reports to you that he has had aches and pains in his muscles for the past seven days. A blood test shows increased levels of creatine kinase MM, fatty acids and also myoglobin. A second blood sample, this time taken after an overnight fast, revealed low levels of blood glucose and elevated very low density lipoprotein (VLDL). This patient most likely has which of the following conditions?

Explanation

Diseases of carnitine shuttle
Systemic primary carnitine deficiency: SLC22A5 gene on chromosome 5q31.1, renal re-uptake transporter OCTN2 (Na+-cotransport). Frequency Faroe Islands 1 in every 500, otherwise 1 in several 10000. OMIM #212140.
Hypoketotic hypoglycemia, Reye-syndrom like episodes, lethargy, somnolence, hepato- and cardiomegaly.
Treatment: oral supplementation of carnitine
Carnitine palmitoyltransferase I deficiency: hypoketotic hypoglycemia, Reye-syndrom like episodes,
hepatomegaly, muscle weakness. OMIM #255120.
Treatment: prevent hypoglycemia with short- and medium-chain fa in diet
Carnitine-acylcarnitine translocase deficiency: Presents within hours of birth with seizures, bradycardia, breathing problems, hypoketotic hypoglycemia, hyperammonemia, hepatomegaly, cardiomyopathy, muscle weakness, sudden infant death. OMIM #212138.
Treatment: low lipid intake, medium chain fa, carnitine, avoid strenuous exercise.
Carnitine palmitoyltransferase II deficiency: Three forms:
Adult: OMIM #255110. Muscle problems (myalgia, rhabdomyolysis, myoglobinuria) during attacks, otherwise normal. Attacks induced by exercise, fasting, high-fat diet, infection. Highly variable age of onset, | more strongly affected.
Infantile: OMIM #600649. Age of onset usually _ 1a, but sometimes later. Hypoketotic hypoglycemia, loss of consciousness and seizures, hepato- and cardiomegaly.
Neonate: OMIM #608836. Onset hours to days after birth, rapidly fatal from cardiac, respiratory or liver failure.
Neuronal migration defects, kidney dysorganization. carnitine formed in liver and kidney from Lys and Met
supplementation not required in healthy individual 12 C-atoms pass membrane by diffusion
distribution of acyl-CoA between cytosol (anabolic) and mito (catabolic)
rate-limiting step of FA breakdown!
( slide 20-22 F.A metab-BUX)

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7. Treatment of hypercholesterolemia requires knowledge of the control of HMG-CoA reductase activity and LDL receptor (LDLR) levels. Which of the following statements is correct concerning HMG-CoA reductase and the LDLR?

Explanation

When the LDL receptor (LDLR) is down-regulated, it means that there are low levels of LDL cholesterol being taken up by the cell. In this situation, the cell requires more cholesterol for its functions. HMG-CoA reductase is the enzyme responsible for the synthesis of cholesterol in the cell. Therefore, when the LDLR is down-regulated and the cell requires cholesterol, HMG-CoA reductase is activated to produce more cholesterol. This statement correctly explains the relationship between HMG-CoA reductase, LDLR, and cholesterol synthesis in the cell.

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8. A 22-year-old woman with poorly controlled gestational diabetes delivers a large -for­gestational-age infant at 24 weeks. Within six hours of birth the baby develops respiratory difficulties associated with rapid respiration and cyanosis. Which of the following substances is most likely deficient in this newborn?

Explanation

Respiratory Distress Syndrome ***Prevalent in premature infants
Due to a deficiency in synthesis of lung surfactant
The major constituents of surfactant are **dipalmitoylphosphatidylcholine**, phosphatidylglycerol, apoproteins (surfactant proteins:Sp A,B,C) and cholesterol
(slide 15 Memb Lip-Laville)

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9. Which of the following organelles, which is defective in Gauchers disease, contains enzymes that degrade complex carbohydrates, proteins and complex lipids?

Explanation

Gaucher's disease is a genetic disease in which lipids accumulates in cells and certain organs. Gaucher's disease is the most common of the lysosomal storage diseases. It is characterized by bruising, fatigue, anemia, low platelets, and enlargement of the liver and spleen. It is caused by a hereditary deficiency of the enzyme glucosylceramidase. The enzyme acts on the fatty acid glucosylceramide. When the enzyme is defective, glucosylceramide accumulates, particularly in white blood cells, most often macrophages (mononuclear leukocytes). Glucosylceramidase can collect in the spleen, liver, kidneys, lungs, brain and bone marrow.
Symptoms may include enlarged spleen and liver, liver malfunction, skeletal disorders and bone lesions that may be painful, severe neurologic complications, swelling of lymph nodes and (occasionally) adjacent joints, distended abdomen, a brownish tint to the skin, anemia, low platelets and yellow fatty deposits on the sclera. Persons affected most seriously may also be more susceptible to infection. Some forms of Gaucher's disease may be treated with enzyme replacement therapy.

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10. Inhibiting the rate limiting enzyme of cholesterol biosynthesis would be beneficiary in lowering blood cholesterol levels by one of the following mechanisms:

Explanation

Inhibiting the formation of mevalonate is beneficial in lowering blood cholesterol levels because mevalonate is a precursor molecule in the cholesterol biosynthesis pathway. By inhibiting its formation, the production of cholesterol is also inhibited, leading to lower blood cholesterol levels. Mevalonate is converted to HMG-CoA, which is further converted into cholesterol. Therefore, inhibiting the formation of mevalonate indirectly inhibits the formation of cholesterol.

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11. Which of the following disorders of glucocerebrosidase metabolism can be treated by bone marrow transplant?

Explanation

Successful bone marrow transplantation cures the non-neurological manifestations of the disease, because it introduces a monocyte population with active beta-glucosidase.

Nieman pick = sphingomylen

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12. Patients with hypothyroidism also present with secondary hypercholesterolemia. One of the reasons for this is:

Explanation

Cholesterol 7 alpha-hydroxylase is the rate-limiting enzyme in the synthesis of bile acid from cholesterol via the classic pathway, catalyzing the formation of 7-alpha-hydroxycholesterol. CYP7A1 is a cytochrome P450 heme enzyme that oxidizes cholesterol using molecular oxygen.
It is downregulated by Sterol regulatory element-binding proteins (SREBP) when plasma cholesterol levels are low. It is upregulated by the nuclear receptor LXR (liver X receptor) when cholesterol (to be specific, oxysterol) levels are high.[2]
The effect of this upregulation is to increase the production of bile acids and reduce the level of cholesterol in hepatocytes.

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13. Lipoprotein lipase is a very important enzyme in lipid metabolism. Found on many tissues in the body its main function is to facilitate the fatty acid uptake in these tissues. In a patient with severely decreased insulin output after a meal, what would you expect to be the metabolic outcome?

Explanation

Lipoprotein lipase is responsible for facilitating the uptake of fatty acids in tissues, including adipose tissue. When there is severely decreased insulin output after a meal, the function of adipose tissue lipoprotein lipase is impaired. As a result, there is a lack of fatty acid uptake in adipose tissue, leading to high levels of triglycerides in the plasma. This occurs because the fatty acids are not being properly utilized and stored in adipose tissue, causing them to remain in the bloodstream.

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14. What is the importance of citrate in fatty acid metabolism?

Explanation

FA synthesis and b-oxidation must not occur at the same time (futile cycle)
Compartmentalization: FA synthesis in cytosol, breakdown in mitocondria
Malonyl-CoA (substrate for FA synthesis) shuts down carnitine shuttle (rate-limiting step of FA breakdown)
FA synthesis regulated at acetyl-CoA carboxylase:
citrate signals good nutrition: allosteric
insulin=dephosphorylation=activation
glucagon + adrenalin=inc cAMP =phosphorylation=
inactivation
gene expression: insulin", glucagon#
( slide 57 F.A metab-BUX)

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15. A patient presents to your clinic complaining of weakness and pain in the muscle and a general lack of energy. A blood test shows that he has high levels of creatine kinase and myoglobin. Urine analysis reveals very low levels of acetoacetate. This patient most likely has which of the following?

Explanation

Diseases of carnitine shuttle
Systemic primary carnitine deficiency: SLC22A5 gene on chromosome 5q31.1, renal re-uptake transporter OCTN2 (Na+-cotransport). Frequency Faroe Islands 1 in every 500, otherwise 1 in several 10000. OMIM #212140.
Hypoketotic hypoglycemia, Reye-syndrom like episodes, lethargy, somnolence, hepato- and cardiomegaly.
Treatment: oral supplementation of carnitine
Carnitine palmitoyltransferase I deficiency: hypoketotic hypoglycemia, Reye-syndrom like episodes,
hepatomegaly, muscle weakness. OMIM #255120.
Treatment: prevent hypoglycemia with short- and medium-chain fa in diet
Carnitine-acylcarnitine translocase deficiency: Presents within hours of birth with seizures, bradycardia, breathing problems, hypoketotic hypoglycemia, hyperammonemia, hepatomegaly, cardiomyopathy, muscle weakness, sudden infant death. OMIM #212138.
Treatment: low lipid intake, medium chain fa, carnitine, avoid strenuous exercise.
Carnitine palmitoyltransferase II deficiency: Three forms:
Adult: OMIM #255110. Muscle problems (myalgia, rhabdomyolysis, myoglobinuria) during attacks, otherwise normal. Attacks induced by exercise, fasting, high-fat diet, infection. Highly variable age of onset, | more strongly affected.
Infantile: OMIM #600649. Age of onset usually _ 1a, but sometimes later. Hypoketotic hypoglycemia, loss of consciousness and seizures, hepato- and cardiomegaly.
Neonate: OMIM #608836. Onset hours to days after birth, rapidly fatal from cardiac, respiratory or liver failure.
Neuronal migration defects, kidney dysorganization. carnitine formed in liver and kidney from Lys and Met
supplementation not required in healthy individual 12 C-atoms pass membrane by diffusion
distribution of acyl-CoA between cytosol (anabolic) and mito (catabolic)
rate-limiting step of FA breakdown! ( slide 20-22 F.A metab-BUX)

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16. Which of the following phospholipids is released by phagocytic cells and leads to superoxide radical production in alveoli macrophages?

Explanation

Platelet activating factor (PAF)
Hormone released from phagocytic cells binds to surface receptors
Causes platelets to aggregate and degranulate. It binds to surface receptors resulting in thrombotic and inflammatory events and anaphylactic reactions
Causes neutrophils and alveoli macrophages to produce superoxide radicals (useful for killing bacteria) (slide 18 Memb Lip-Laville)

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17. When excess acetyl-CoA, produced by the liver, cannot be used by the TCA cycle, it accumulates in the body as:

Explanation

When excess acetyl-CoA cannot be utilized by the TCA cycle, it is converted into p-hydroxybutarate. This conversion occurs in the liver and is part of a metabolic pathway known as ketogenesis. p-hydroxybutarate is one of the ketone bodies produced during this process. Ketone bodies can be used as an alternative fuel source by various tissues, including the brain, when glucose availability is limited. Therefore, when excess acetyl-CoA accumulates, it is converted into p-hydroxybutarate to be used as an energy source.

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18. A mother takes her one-year-old daughter to the pediatric clinic because she observes that the child keeps walking into objects and does not respond when she talks to her. On examination the pediatrician notes that she has problems with her hearing and cannot see. Other observations included muscle weakness and slow mental and motor development. This patient most likely has which one of the following diseases:

Explanation

The patient most likely has Krabbes disease based on the symptoms described. Krabbes disease is a rare genetic disorder that affects the nervous system. It is characterized by the loss of myelin, the protective covering of nerve cells, which leads to problems with hearing and vision, muscle weakness, and delayed development. The symptoms mentioned in the question, such as walking into objects, not responding to sounds, muscle weakness, and slow mental and motor development, align with the characteristic features of Krabbes disease.

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19. In patients with systemic lupus erythematosus, autoantibodies are produced to a membrane lipid in platelets, resulting in blood clotting disorders. This membrane lipid is:

Explanation

Cardiolipin: Found in abundance in the inner mitochondrial membrane where it maintains certain respiratory complexes on the electron transport chain
The only human glycerophospholipid that is antigenic. It is recognized by antibodies raised against Trepanoma Pallidum. = Autoimmune diseases.
(slide 13 Memb Lip-Laville)

Cardiolipin from a cow heart is used as an antigen in the Wassermann test for syphilis. Anti-cardiolipin antibodies can also be increased in numerous other conditions, including systemic lupus erythematosus, malaria and tuberculosis, so this test is not specific. (wikipedia)

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20. The reducing equivalents necessary for fatty acid synthesis are produced during the conversion of:

Explanation

During the conversion of glucose-6-phosphate to ribulose-5-phosphate in the pentose phosphate pathway, NADPH is produced. NADPH is a reducing equivalent and is required for fatty acid synthesis. Therefore, this conversion provides the necessary reducing equivalents for fatty acid synthesis.

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21. Some of the apoproteins have very important functions in lipoprotein metabolism. Which of the following apoproteins is an important activator of lecithin cholesterol acyl transferase (LCAT)?

Explanation

Apo Al is an important activator of lecithin cholesterol acyl transferase (LCAT).

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22. A deficiency in the activity of medium chain acyl-CoA dehydrogenase, an enzyme in the pathway for beta-oxidation of fatty acids, is corrected by large doses of its vitamin component in some patients. Which of the following compounds is the vitamin component of this enzyme?

Explanation

The signs and symptoms of riboflavin deficiency typically include sore throat with redness and swelling of the mouth and throat mucosa, cheilosis and angular stomatitis (cracking of the lips and corners of the mouth), glossitis (magenta tongue with atrophy), seborrheic dermatitis or pseudo-syphilis (moist, scaly skin particularly affecting the scrotum or labia majora and the nasolabial folds), and a decreased red blood cell count with normal cell size and hemoglobin content (normochromic normocytic anemia).

Persons with chronic alcoholism can have impaired absorption of riboflavin and other vitamins such as thiamine (see Wernicke's encephalopathy).

USMLE step 1 book indicates that corneal vascularization is also a presentation for B2 deficiency.

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23. Cytidine nucleotides are involved in phospholipid synthesis because:

Explanation

Cytidine nucleotides are involved in phospholipid synthesis because they play a role in the activation of choline, ethanolamine, and diacylglycerol (DAG). These molecules are important components in the synthesis of phospholipids, which are essential for building cell membranes. By activating choline, ethanolamine, and DAG, cytidine nucleotides contribute to the production of phospholipids, ensuring the proper structure and function of cell membranes.

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24. Prostaglandins are synthesized from which of the following essential fatty acids?

Explanation

Prostaglandins are synthesized from linolenic acid, an essential fatty acid. Linolenic acid is converted into other fatty acids, such as arachidonic acid, which then serve as precursors for prostaglandin synthesis. Prostaglandins are important signaling molecules that play a role in various physiological processes, including inflammation, blood clotting, and smooth muscle contraction.

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During starvation ketone bodies are synthesized in one of the...
Which of the following phospholipids induces hypersensitivity,...
The site of action of the nonsteroidal anti-inflammatory drugs is:
A 29-year-old male decides to go on the Atkins diet. After...
A 5-year old female is presented with hepatosplenomegaly, abnormal...
A patient reports to you that he has had aches and pains in his...
Treatment of hypercholesterolemia requires knowledge of the control of...
A 22-year-old woman with poorly controlled gestational diabetes...
Which of the following organelles, which is defective in Gauchers...
Inhibiting the rate limiting enzyme of cholesterol biosynthesis would...
Which of the following disorders of glucocerebrosidase metabolism...
Patients with hypothyroidism also present with secondary...
Lipoprotein lipase is a very important enzyme in lipid metabolism....
What is the importance of citrate in fatty acid metabolism?
A patient presents to your clinic complaining of weakness and pain in...
Which of the following phospholipids is released by phagocytic cells...
When excess acetyl-CoA, produced by the liver, cannot be used by the...
A mother takes her one-year-old daughter to the pediatric clinic...
In patients with systemic lupus erythematosus, autoantibodies are...
The reducing equivalents necessary for fatty acid synthesis are...
Some of the apoproteins have very important functions in lipoprotein...
A deficiency in the activity of medium chain acyl-CoA dehydrogenase,...
Cytidine nucleotides are involved in phospholipid synthesis because:
Prostaglandins are synthesized from which of the following essential...
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