Biosynthesis of cholesterol:
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
Cholesterol is:
a protein
a lipid
an amino acid
composed of four rings and a side chain
composed of twenty seven carbon atoms
The key enzyme of cholesterol biosynthesis is:
Thiolase
HMG-CoA synthase
HMG-CoA reductase
Mevalonate kinase
Squalene synthetase
The biosynthesis of triacylglycerols requires:
phospholipase B
phospholipase D
cholesteryl ester molecules
phosphorylated triose (glycerol 3-phosphate)
fatty acids in the form of acyl-CoA
Which of the following is true?
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
Which of the following compounds is not a lipid?
cholesterol
glycerol
triacylglycerol
sphingomyelin
phosphatidylcholine
Which is the main apoprotein in LDL, recognized by the LDL receptors:
Apo B-48
Apo E
Apo B-100
Apo C-II
Which is the main regulatory enzyme in cholesterol biosynthesis:
Which of the following compounds are cholesterol derivatives:
Bile acids
Vit. D3
steroid hormones
HMG-CoA
ketone bodies
Which of the following is TRUE:
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
Which of the following apoproteins activates lipoprotein lipase:
What is the effect of the following hormones on lipolysis‘?
lipolysis is stimulated by adrenaline
lipolysis is inhibited by adrenaline
lipolysis is inhibited by insulin
lipolysis is stimulated by insulin
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
Which of the following is not true
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
Which of the following substances are ketone bodies
Acetone
Acetoacetate
Acetyl-CoA
Pyruvate
3-hydroxybutyrate
Which of the following statements about LDL are true?
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
Which of the following statements about eicosanoids are FALSE?
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
Which of the following compounds is not a glycerophospholipid?
Phosphatidylinositol
Phosphatidylserine
Lecithin
Ganglioside
Which of the following statements about biosynthesis of fatty acids and B-oxidation are TRUE
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
Which of the following statements about ketone bodies are TRUE?
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
Which of the following about activation of free fatty acids is true?
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
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
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
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
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
Which is the only one glucogenic metabolite from the free fatty acids metabolism
acyl-CoA
acetyl-CoA
malonyl-CoA
propionyl-CoA
Which of the following statements about acyl-CoA synthase are NOT TRUE?
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
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
ketogenesis occurs in the extrahepatic tissues
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
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
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
Which phospholipase is essential for initializing the biosynthesis of eicosanoids?
phospholipase A1
phospholipase A2
phospholipase C
Lipolysis:
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
Which of the following enzymes do not participate in β-oxidation?
HMG-CoA syntahse
Thioesterase
Acyl-CoA dehydrogenase
hydratase
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
Which of the following enzymes participate in β-oxidation
acyl-CoA dehydrogenase
3-hydroxyacyl-CoA dehydrogenase
acetyl-CoA carboxylase
thiolase
Which of the following statements is TRUE
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
HMG-CoA reductase:
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
Which of the following statements are FALSE?
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
Hormone-sensitive lipase
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
Which of the following compounds is not a phospholipid
Phosphatidylcortisol
Phosphatidylcholine
Glycerol-3-Phosphate
1, 2 diacylglycerol
Which of the following statements about chylomicrons are true?
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
Ketone bodies
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
How is acetyl-CoA carboxylase (ACC) regulated?
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
Cholesterol
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
Which reactions can provide NADPH + H+, necessary both for the synthesis of fatty acids and cholesterol?
α-ketoglutarate dehydrogenase complex
cytosolic isocitrate dehydrogenase
malic enzyme
malate dehydrogenase
pentose phosphate pathway
