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Biochemistry Exam 4 Lipid Metabolism- PMU 2nd Year

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Biochemistry Exam 4 Lipid Metabolism- PMU 2nd Year

Question 1 of 46

1

Biosynthesis of cholesterol:

Select one or more of the following:

  • 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

Explanation

Question 2 of 46

1

Cholesterol is:

Select one or more of the following:

  • a protein

  • a lipid

  • an amino acid

  • composed of four rings and a side chain

  • composed of twenty seven carbon atoms

Explanation

Question 3 of 46

1

The key enzyme of cholesterol biosynthesis is:

Select one or more of the following:

  • Thiolase

  • HMG-CoA synthase

  • HMG-CoA reductase

  • Mevalonate kinase

  • Squalene synthetase

Explanation

Question 4 of 46

1

The biosynthesis of triacylglycerols requires:

Select one or more of the following:

  • phospholipase B

  • phospholipase D

  • cholesteryl ester molecules

  • phosphorylated triose (glycerol 3-phosphate)

  • fatty acids in the form of acyl-CoA

Explanation

Question 5 of 46

1

Which of the following is true?

Select one or more of the following:

  • 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

Explanation

Question 6 of 46

1

Which of the following compounds is not a lipid?

Select one or more of the following:

  • cholesterol

  • glycerol

  • triacylglycerol

  • sphingomyelin

  • phosphatidylcholine

Explanation

Question 7 of 46

1

Which is the main apoprotein in LDL, recognized by the LDL receptors:

Select one or more of the following:

  • Apo B-48

  • Apo E

  • Apo B-100

  • Apo C-II

Explanation

Question 8 of 46

1

Which is the main regulatory enzyme in cholesterol biosynthesis:

Select one or more of the following:

  • Thiolase

  • HMG-CoA reductase

  • HMG-CoA synthase

  • Mevalonate kinase

Explanation

Question 9 of 46

1

Which of the following compounds are cholesterol derivatives:

Select one or more of the following:

  • Bile acids

  • Vit. D3

  • steroid hormones

  • HMG-CoA

  • ketone bodies

Explanation

Question 10 of 46

1

Which of the following is TRUE:

Select one or more of the following:

  • 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

Explanation

Question 11 of 46

1

Which of the following apoproteins activates lipoprotein lipase:

Select one or more of the following:

  • Apo B-48

  • Apo E

  • Apo B-100

  • Apo C-II

Explanation

Question 12 of 46

1

What is the effect of the following hormones on lipolysis‘?

Select one or more of the following:

  • lipolysis is stimulated by adrenaline

  • lipolysis is inhibited by adrenaline

  • lipolysis is inhibited by insulin

  • lipolysis is stimulated by insulin

Explanation

Question 13 of 46

1

Which of the following is TRUE:

Select one or more of the following:

  • 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

Explanation

Question 14 of 46

1

Which of the following is not true

Select one or more of the following:

  • 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

Explanation

Question 15 of 46

1

Which of the following substances are ketone bodies

Select one or more of the following:

  • Acetone

  • Acetoacetate

  • Acetyl-CoA

  • Pyruvate

  • 3-hydroxybutyrate

Explanation

Question 16 of 46

1

Which of the following statements about LDL are true?

Select one or more of the following:

  • 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

Explanation

Question 17 of 46

1

Which of the following statements about eicosanoids are FALSE?

Select one or more of the following:

  • 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

Explanation

Question 18 of 46

1

Which of the following compounds is not a glycerophospholipid?

Select one or more of the following:

  • Phosphatidylinositol

  • Phosphatidylserine

  • Lecithin

  • Ganglioside

Explanation

Question 19 of 46

1

Which of the following statements about biosynthesis of fatty acids and B-oxidation are TRUE

Select one or more of the following:

  • 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

Explanation

Question 20 of 46

1

Which of the following statements about ketone bodies are TRUE?

Select one or more of the following:

  • 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

Explanation

Question 21 of 46

1

Which of the following about activation of free fatty acids is true?

Select one or more of the following:

  • 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

Explanation

Question 22 of 46

1

Which of the following is true?

Select one or more of the following:

  • 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

Explanation

Question 23 of 46

1

Which of the following is true?

Select one or more of the following:

  • 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

Explanation

Question 24 of 46

1

Which of the following is true?

Select one or more of the following:

  • 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

Explanation

Question 25 of 46

1

HMG-CoA reductase

Select one or more of the following:

  • 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

Explanation

Question 26 of 46

1

Which is the only one glucogenic metabolite from the free fatty acids metabolism

Select one or more of the following:

  • acyl-CoA

  • acetyl-CoA

  • malonyl-CoA

  • propionyl-CoA

Explanation

Question 27 of 46

1

Which of the following statements about acyl-CoA synthase are NOT TRUE?

Select one or more of the following:

  • 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

Explanation

Question 28 of 46

1

Which of the following is TRUE:

Select one or more of the following:

  • 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

Explanation

Question 29 of 46

1

Which of the following is TRUE:

Select one or more of the following:

  • 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

Explanation

Question 30 of 46

1

Which of the following is TRUE:

Select one or more of the following:

  • 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

Explanation

Question 31 of 46

1

Which of the following is TRUE:

Select one or more of the following:

  • 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

Explanation

Question 32 of 46

1

Which phospholipase is essential for initializing the biosynthesis of eicosanoids?

Select one or more of the following:

  • phospholipase A1

  • phospholipase A2

  • phospholipase C

  • phospholipase D

Explanation

Question 33 of 46

1

Lipolysis:

Select one or more of the following:

  • 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

Explanation

Question 34 of 46

1

Which of the following enzymes do not participate in β-oxidation?

Select one or more of the following:

  • HMG-CoA syntahse

  • Thiolase

  • Thioesterase

  • Acyl-CoA dehydrogenase

  • hydratase

Explanation

Question 35 of 46

1

Which of the following is TRUE:

Select one or more of the following:

  • 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

Explanation

Question 36 of 46

1

Which of the following enzymes participate in β-oxidation

Select one or more of the following:

  • acyl-CoA dehydrogenase

  • 3-hydroxyacyl-CoA dehydrogenase

  • acetyl-CoA carboxylase

  • thiolase

  • HMG-CoA reductase

Explanation

Question 37 of 46

1

Which of the following statements is TRUE

Select one or more of the following:

  • 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

Explanation

Question 38 of 46

1

HMG-CoA reductase:

Select one or more of the following:

  • 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

Explanation

Question 39 of 46

1

Which of the following statements are FALSE?

Select one or more of the following:

  • 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

Explanation

Question 40 of 46

1

Hormone-sensitive lipase

Select one or more of the following:

  • 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

Explanation

Question 41 of 46

1

Which of the following compounds is not a phospholipid

Select one or more of the following:

  • Phosphatidylcortisol

  • Phosphatidylcholine

  • Glycerol-3-Phosphate

  • 1, 2 diacylglycerol

Explanation

Question 42 of 46

1

Which of the following statements about chylomicrons are true?

Select one or more of the following:

  • 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

Explanation

Question 43 of 46

1

Ketone bodies

Select one or more of the following:

  • 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

Explanation

Question 44 of 46

1

How is acetyl-CoA carboxylase (ACC) regulated?

Select one or more of the following:

  • 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

Explanation

Question 45 of 46

1

Cholesterol

Select one or more of the following:

  • 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

Explanation

Question 46 of 46

1

Which reactions can provide NADPH + H+, necessary both for the synthesis of fatty acids and cholesterol?

Select one or more of the following:

  • α-ketoglutarate dehydrogenase complex

  • cytosolic isocitrate dehydrogenase

  • malic enzyme

  • malate dehydrogenase

  • pentose phosphate pathway

Explanation

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