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Biochemistry Exam 4 Lipid Metabolism- PMU 2nd Year

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Biochemistry Exam 4 Lipid Metabolism- PMU 2nd Year
Med Student
Quiz by Med Student , updated more than 1 year ago
Med Student
Created by Med Student almost 9 years ago
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Resource summary

Question 1

Question
Biosynthesis of cholesterol:
Answer
  • occurs in mitochondria
  • occurs in cytosol
  • consumes hydrogen atoms in the form of NADPH
  • is accompanied with storage of energy in the form of ATP
  • requires a large quantity of ATP

Question 2

Question
Cholesterol is:
Answer
  • a protein
  • a lipid
  • an amino acid
  • composed of four rings and a side chain
  • composed of twenty seven carbon atoms

Question 3

Question
The key enzyme of cholesterol biosynthesis is:
Answer
  • Thiolase
  • HMG-CoA synthase
  • HMG-CoA reductase
  • Mevalonate kinase
  • Squalene synthetase

Question 4

Question
The biosynthesis of triacylglycerols requires:
Answer
  • phospholipase B
  • phospholipase D
  • cholesteryl ester molecules
  • phosphorylated triose (glycerol 3-phosphate)
  • fatty acids in the form of acyl-CoA

Question 5

Question
Which of the following is true?
Answer
  • Triacylglycerols are formed by acylation of triose phosphates
  • Triacylglycerols are hydrolyzed by lipases
  • Triacylglycerols are polymerized into glycogen
  • Triacylglycerols are storage lipids stored in adipose tissue
  • Triacylglycerols are degraded by acyl-CoA synthase

Question 6

Question
Which of the following compounds is not a lipid?
Answer
  • cholesterol
  • glycerol
  • triacylglycerol
  • sphingomyelin
  • phosphatidylcholine

Question 7

Question
Which is the main apoprotein in LDL, recognized by the LDL receptors:
Answer
  • Apo B-48
  • Apo E
  • Apo B-100
  • Apo C-II

Question 8

Question
Which is the main regulatory enzyme in cholesterol biosynthesis:
Answer
  • Thiolase
  • HMG-CoA reductase
  • HMG-CoA synthase
  • Mevalonate kinase

Question 9

Question
Which of the following compounds are cholesterol derivatives:
Answer
  • Bile acids
  • Vit. D3
  • steroid hormones
  • HMG-CoA
  • ketone bodies

Question 10

Question
Which of the following is TRUE:
Answer
  • oxidation of fatty acids occurs in mitochondria
  • oxidation of fatty acids occurs in cytosol
  • oxidation of fatty acids generates FADH2 and NADH
  • oxidation of fatty acids is catalyzed by a multifunctionai protein with seven enzyme activities

Question 11

Question
Which of the following apoproteins activates lipoprotein lipase:
Answer
  • Apo B-48
  • Apo E
  • Apo B-100
  • Apo C-II

Question 12

Question
What is the effect of the following hormones on lipolysis‘?
Answer
  • lipolysis is stimulated by adrenaline
  • lipolysis is inhibited by adrenaline
  • lipolysis is inhibited by insulin
  • lipolysis is stimulated by insulin

Question 13

Question
Which of the following is TRUE:
Answer
  • VLDL transport triacylglycerols from the liver to the extrahepatic tissues
  • VLDL deliver cholesterol to the tissues
  • LDL deliver cholesterol to the tissues
  • HDL remove cholesterol from the tissues and return it to the liver for excretion

Question 14

Question
Which of the following is not true
Answer
  • cholesterol is an essential structural component of cellular membranes
  • cholesterol is the precursor of steroid hormones, bile acids and vit D3
  • HMG-CoA synthase is the main regulatory enzyme in the pathway of cholesterol biosynthesis
  • HMG-CoA reductase activity is increased by insulin

Question 15

Question
Which of the following substances are ketone bodies
Answer
  • Acetone
  • Acetoacetate
  • Acetyl-CoA
  • Pyruvate
  • 3-hydroxybutyrate

Question 16

Question
Which of the following statements about LDL are true?
Answer
  • contain only apo B-100
  • contain apo B-100 and apo E
  • they transport cholesterol from the extrahepatic tissues to the liver
  • they transport cholesterol from the liver to the extrahepatic tissues
  • they transport triacylglycerols from the liver to the extrahepatic tissues

Question 17

Question
Which of the following statements about eicosanoids are FALSE?
Answer
  • they are synthesized and secreted by separate glands
  • they have an escpecially fast metabolism
  • corticosteroids can block their production
  • thromboxanes are synthesized through the lipoxygenase pathway
  • derive only from the arachidonic acid

Question 18

Question
Which of the following compounds is not a glycerophospholipid?
Answer
  • Phosphatidylinositol
  • Phosphatidylserine
  • Lecithin
  • Ganglioside

Question 19

Question
Which of the following statements about biosynthesis of fatty acids and B-oxidation are TRUE
Answer
  • Acetyl-CoA, which serves as substrate for the synthesis, derives from B-oxidation
  • B-oxidation and lipogenesis are controlled reciprocally
  • Malonyl-CoA inhibits carnitine-palmitoyl transferase 2 and thus B-oxidation
  • Citrate is an activator of acetyl-CoA carboxylase

Question 20

Question
Which of the following statements about ketone bodies are TRUE?
Answer
  • Ketogenesis occurs when there is an increase in the level of free fatty acids
  • All ketone bodies serve as an energy fuel for the extrahepatic tissues
  • Acetone and B-hydroxybutirate serve as energy fuel but acetoacetate does not
  • Ketone bodies are physiologically present in blood but in a very low concentration
  • The abnormal increase in the concentration of ketone bodies can cause ketoacidosis
  • HMG-CoA synthase and HMG-CoA lyase are enzymes from the pathway of ketogenesis

Question 21

Question
Which of the following about activation of free fatty acids is true?
Answer
  • an enzyme, acetyl-CoA carboxylase, is needed
  • an enzyme, acyl-CoA synthetase, is needed
  • the enzyme is placed in inner mitochondrial membrane
  • the enzyme is placed in outer mitochondrial membrane
  • ATP is needed as energy donor

Question 22

Question
Which of the following is true?
Answer
  • long-chain fatty acids are oxidized in mitochondrial matrix
  • peroxisomes oxidize very long-chain fatty acids
  • β-oxidation leads to an activated energy consumption
  • oxidation of fatty acids produces large quantity of NADH and FADH2 which leads to large production of ATP
  • oxidation of fatty acids produces large quantity of NADPH, which leads to acceleration of anabolic processes

Question 23

Question
Which of the following is true?
Answer
  • NADPH for fatty acids biosynthesis is generated by the pentose phosphate pathway, mainly
  • NADPH is generated in the B-oxidation, mainly
  • hydrogen atoms, needed for reductive reactions in fatty acids biosynthesis, are produced by the respiratory chain
  • enzyme activities of the acyl synthase complex need NADPH
  • NADPH is also generated by the “malic” enzyme, placed in cytosol

Question 24

Question
Which of the following is true?
Answer
  • ketone bodies are the main energy source for skeletal muscles
  • ketone bodies are an alternative energy source for extrahepatic tissues
  • ketone bodies enter glycolysis after activation
  • higher than normal quantities of ketone bodies in blood cause a condition called ketosis
  • ketosis is mild in starvation but severe in diabetes mellitus

Question 25

Question
HMG-CoA reductase
Answer
  • is inhibited by lipids and cholesterol
  • is activated by phophorylation
  • insulin serves both as its activator but also as an inducer an gene level
  • in hypercholesterolaemia can be pharmologically affected by statins

Question 26

Question
Which is the only one glucogenic metabolite from the free fatty acids metabolism
Answer
  • acyl-CoA
  • acetyl-CoA
  • malonyl-CoA
  • propionyl-CoA

Question 27

Question
Which of the following statements about acyl-CoA synthase are NOT TRUE?
Answer
  • in mammals it is a multifunctional complex, organized as a hetrodimer
  • it functions together with acyl carrier protein, which contains 4-phosphopantethine as a prosthetic group
  • ketoacyl reductase uses NADH+H+ as a cofactor
  • the last enzyme is thioesterase

Question 28

Question
Which of the following is TRUE:
Answer
  • free fatty acids that arise from Iipolysis of triacylglycerol in adipose tissue are the precursors of ketone bodies
  • in starvation the insulin/glucagon ratio increases
  • ketosis is mild in starvation but severe in diabetes mellitus
  • ketogenesis occurs in the extrahepatic tissues

Question 29

Question
Which of the following is TRUE:
Answer
  • the biosynthesis of fatty acids (lipogenesis) occurs in the cytosol
  • in mammals the fatty acid synthase complex consists of three identical monomers
  • the main source of NADPH for the biosynthcsis of fatty acids is glycolysis
  • acetyl-CoA carboxylase is the main regulatory enzyme in lipogenesis

Question 30

Question
Which of the following is TRUE:
Answer
  • glycerol-3-phosphate and Acyl-CoA are required for the biosynthesis of triacylglycerols
  • glycerol kinase is active in muscle and adipose tissue
  • the degradation of triacylglycerols (lipolysis) is catalyzed by lipase
  • the hormone-sensitive lipase is activated by insulin

Question 31

Question
Which of the following is TRUE:
Answer
  • eicosanoids can be produced from arachidonic acid
  • the NSAIDs like aspirin, ibuprofen and indomethacin activate COX-1 and COX-2
  • arachidonic acid may be obtained from membrane phospholipids by the action of phospholipase A2
  • the cyclooxygenase pathway produces prostaglandins

Question 32

Question
Which phospholipase is essential for initializing the biosynthesis of eicosanoids?
Answer
  • phospholipase A1
  • phospholipase A2
  • phospholipase C
  • phospholipase D

Question 33

Question
Lipolysis:
Answer
  • is the degradation of fatty acids
  • is the degradation of triacylglycerols
  • occurs in the mitochondria
  • occurs in the cytoplasm
  • is activated by epinephrine and glucagon which dephosphorylate the hormone-sensitive lipase

Question 34

Question
Which of the following enzymes do not participate in β-oxidation?
Answer
  • HMG-CoA syntahse
  • Thiolase
  • Thioesterase
  • Acyl-CoA dehydrogenase
  • hydratase

Question 35

Question
Which of the following is TRUE:
Answer
  • the primary bile acids are synthesized in the liver from cholesterol
  • the primary bile acids enter the bile as serine or alanine conjugates
  • the bile acids emulsify dietary lipids in the small intestine and aid their digestion
  • the bile acids emulsify dietary carbohydrates

Question 36

Question
Which of the following enzymes participate in β-oxidation
Answer
  • acyl-CoA dehydrogenase
  • 3-hydroxyacyl-CoA dehydrogenase
  • acetyl-CoA carboxylase
  • thiolase
  • HMG-CoA reductase

Question 37

Question
Which of the following statements is TRUE
Answer
  • the fatty acid synthase complex in mammals is a dimer of two identical monomers
  • the synthesis of fatty acids (lipogenesis) occurs in the cytosol
  • acetyl-CoA carboxylase requires pyridoxal phosphate as a cofactor
  • glucagon activates acetyl-CoA carboxylase by stimulating its phosphorylation

Question 38

Question
HMG-CoA reductase:
Answer
  • is inhibited by bile acids and cholesterol
  • is activated by phosphorylation
  • insulin serves both as its activator, but also as an inducer on gene level
  • in hypercholesterolaemia can be pharmocologically affected by statins

Question 39

Question
Which of the following statements are FALSE?
Answer
  • the levels of leptin in obesity are high and these of adiponectin- low
  • the higher HDL-cholesterol level is, the higher cardio-vascular risk is
  • a defect in LDL-receptors can cause hypercholesterolaemia
  • a deficiency in vitamin D in adults is called rickets
  • cholelithiasis can be caused by impaired ratio between cholesterol and bile acids as well as phospholipids in the gallbladder

Question 40

Question
Hormone-sensitive lipase
Answer
  • is the main regulatory enzyme in β-oxidation
  • is activated by cAMP-dependent protein kinase (PKA)
  • is inhibited by insulin- the activator of phosphodieterase
  • is inhibited by glucagon and the thyroid hormones
  • catalyzes the degradation of monacylglycerols to fatty acid and glycerol
  • functions in the mitochondria

Question 41

Question
Which of the following compounds is not a phospholipid
Answer
  • Phosphatidylcortisol
  • Phosphatidylcholine
  • Glycerol-3-Phosphate
  • 1, 2 diacylglycerol

Question 42

Question
Which of the following statements about chylomicrons are true?
Answer
  • their specific apoprotein is Apo B-100
  • their specific apoprotein is Apo B-48
  • they transport cholesterol from the intestines to the extrahepatic tissues
  • they transport triacylglycerols from the intestines to the extrahepatic tissues
  • they transport triacylglycerols from the liver to the extrahepatic tissues

Question 43

Question
Ketone bodies
Answer
  • are synthesized in the cytoplasm of the hepatocytes
  • can serve as energy source for the brain
  • their synthesis is increased after feeding
  • their synthesis is pathologically increased in diabetes mellitus
  • there is a correlation between their degradation and Krebs cycle

Question 44

Question
How is acetyl-CoA carboxylase (ACC) regulated?
Answer
  • it is inhibited by acetyl-CoA
  • it is inhibited by acyl-CoA
  • it is activated by dephosphorylation
  • it is activated by phosphorylation
  • It is regulated in a coordination with the pyruvate dehydrogenase complex

Question 45

Question
Cholesterol
Answer
  • can be degraded only in the peroxisomes of the liver cell
  • together with the phospholipids is an essential component of the cell membranes
  • is the precursor of ketone bodies
  • the only possible way of its excretion is through bile and bile acids
  • its synthesis is under strict hormonal control realized on the level of HMG-CoA synthase

Question 46

Question
Which reactions can provide NADPH + H+, necessary both for the synthesis of fatty acids and cholesterol?
Answer
  • α-ketoglutarate dehydrogenase complex
  • cytosolic isocitrate dehydrogenase
  • malic enzyme
  • malate dehydrogenase
  • pentose phosphate pathway
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