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Biochemistry (Questions) > Lipids, cholesterol, bile acids > Flashcards

Lipids, cholesterol, bile acids Flashcards

1
Q

Which substrates are necessary for the synthesis of bile salts?

Select one or more:

a. NADPH2
b. NADH2
c. ATP
d. O2
e. H2O

A

a. NADPH2
c. ATP
d. O2

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2
Q

Select the statements valid for the lipoproteins

Select one or more:

a. Their density increases in parallel with their protein content
b. Their density is reciprocally proportional to their lipid content
c. The core non-polar lipids are surrounded by polar lipids
d. All of them contain phospholipids
e. Non-polar interactions bind together the lipids in their structure

A

All correct

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3
Q

Which of the following statements are valid for the apolipoprotein B-100?

Select one or more:

a. It is synthesized in the liver
b. It is recognized by the LDL-receptor
c. It is not present in the structure of VLDL
d. It participates in the liver uptake of chylomicron remnants
e. It is found in the structure of IDL

A

a. It is synthesized in the liver
b. It is recognized by the LDL-receptor
e. It is found in the structure of IDL

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4
Q

Which of the following lipoproteins does not contain triacylglycerols? Select one:

a. Chylomicron
b. HDL3
c. IDL
d. Nascent VLDL
e. VLDL

A

b. HDL3 (for cholesterol only)

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5
Q

Which of the following statements is not valid for the lipoprotein lipase?

Select one:

a. An isoenzyme with a low KM is present in the mammary gland b. It degrades the majority of plasma triacylglycerols
c. It is bound to the luminal surface of the capillary endothelial cells
d. Its activity increases in the fasting state
e. VLDL carries its cofactor

A

d. Its activity increases in the fasting state

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6
Q

Which of the following statements are valid?

Select one or more:

a. The nascent VLDL is formed in the intestinal epithelial cells
b. The VLDL is converted to IDL in the circulation
c. The cells recognize the apo B-100 in the structure of VLDL and take up the lipoprotein through it
d. The lipoprotein lipase reduces the triacylglycerol content of VLDL
e. The apo B-100 of LDL is derived from VLDL

A

b. The VLDL is converted to IDL in the circulation
d. The lipoprotein lipase reduces the triacylglycerol content of VLDL

e. The apo B-100 of LDL is derived from VLDL
=> (ApoB-100 is synthesized by the liver and secreted within VLDLs, which are metabolized in plasma to form LDL)

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7
Q

Which of the following statements is not valid?

Select one:

a. Cholesterol overload inhibits the expression of LDL-receptors
b. Cholesterol overload inhibits the HMG-CoA reductase in the cells
c. In case of cholesterol overproduction cholesteryl esters are formed in the cells as a result of the action of LCAT enzyme
d. The LDL-derived cholesterol affects the cholesterol synthesis in the cells e. The LDL-receptor recognizes the apo B-100

A

c. In case of cholesterol overproduction cholesteryl esters are formed in the cells as a result of the action of LCAT enzyme

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8
Q

Which is the committed step of the cholesterol biosynthesis?

Select one:

a. Mevalonate to 5-phosphomevalonate
b. Acetyl-CoA to acetoacetyl-CoA
c. Acetoacetyl-CoA to 3-hydroxi-3-methyl glutaryl-CoA
d. 5-phosphomevalonate to 5-pyrophosphomevalonate
e. 3-hydroxi-3-methyl glutaryl-CoA to Mevalonate

A

e. 3-hydroxi-3-methyl glutaryl-CoA to Mevalonate

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9
Q

Select the statements valid for the bile acids

Select one or more:

a. The bile acids are synthesized in the intestine
b. In the course of synthesis the polar character of the molecules increases
c. Bile acids are necessary for the solubilization of cholesterol in water phase
d. Deoxycholic acid is one of the primary bile acids
e. Lack of bile acids results in steatorrhea

A

b. In the course of synthesis the polar character of the molecules increases
c. Bile acids are necessary for the solubilization of cholesterol in water phase
e. Lack of bile acids results in steatorrhea

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10
Q

Select the correct statements

Select one or more:

a. The nascent HDL does not contain cholesteryl esters
b. Triacylglycerols are transferred from VLDL to HDL
c. Cholesteryl esters are transferred from VLDL to HDL
d. The hepatic lipase degrades the triacylglycerols in HDL2
e. The HDL-derived cholesterol is taken up by the liver in part in the form of LDL

A

Except Cholesteryl ester…. All correct

(Nascent HDL (High-Density Lipoprotein) Discs Carry Cholesterol to HDL Spheres. Effects of HDL Particle Remodeling on Cholesterol Efflux)

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11
Q

Select the wrong statement

Select one:

a. HDL carries ACAT (acyl-CoA cholesterol acyltransferase)
b. HDL takes up triacylglycerols with the help of cholesteryl ester transfer protein
c. HDL2 delivers cholesterol to the liver
d. The HDL contains apo-A1
e. The triacylglycerol content of HDL2 is higher than that of HDL3

A

a. HDL carries ACAT (acyl-CoA cholesterol acyltransferase)

(LCAT is an enzyme synthesized mostly in the liver; it circulates in the plasma associated with HDL particles and, to a lesser extent, with LDL particles
=> ACAT activities are present in various tissues such as liver, intestines, adrenal glands, and aorta and are involved in intracellular cholesterol storage, lipoprotein assembly, steroid hormone production, and dietary cholesterol absorption)

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12
Q

At least how many glucose molecules are necessary to provide the carbon atoms for the biosynthesis of one cholesterol molecule in mammalian tissues?

Select one:

a. 7
b. 8
c. 9
d. 6
e. 5

A

c. 9

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13
Q

How many Acetyl-CoA molecules are needed for the synthesis of one molecule of cholesterol?
Select one:

a. 10
b. 18
c. 20
d. 25

A

b. 18

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14
Q

Which of the following statements are valid for the ABCA1 transporter?

Select one or more:

a. It is the major transporter of bile salts
b. Its deficiency causes atherosclerosis because of the elevated levels of LDL-cholesterol
c. High intracellular cholesterol content stimulates its transcription
d. It is necessary for the efflux of cholesterol from the cells
e. It is a scavenger receptor for LDL
f. HDL binds to it

A

c. High intracellular cholesterol content stimulates its transcription
d. It is necessary for the efflux of cholesterol from the cells
f. HDL binds to it

(ABCA1 - pump cholesterol out)

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15
Q

Which processes are modulated by the amount of intracellular free cholesterol?

Select one or more:

a. synthesis of bile acids
b. down-regulation of LDL-receptors in the membrane
c. transfer of cholesterol from the membrane into HDL
d. cholesterol synthesis
e. synthesis of cholesterol esters

A

Except for ‘down-regulation…’ all correct

only affect LDL concentration

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16
Q

Which carbon atom carries the hydroxylic group in cholesterol?
Select one:

a. C-3
b. C-7
c. C-10
d. C-21
e. C-27

A

C-3

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17
Q

Which statements are true?

Select one or more:

a. Cholesterol is formed from HMG-CoA synthesized in the mitochondria
b. Cholesterol is formed from HMG-CoA synthesized in the cytosol
c. Mevalonate is formed from HMG-CoA by decarboxylation
d. NADPH is needed for mevalonate synthesis
e. Acetyl-CoA for cholesterol synthesis originates from mitochondria

A

b. Cholesterol is formed from HMG-CoA synthesized in the cytosol
d. NADPH is needed for mevalonate synthesis
e. Acetyl-CoA for cholesterol synthesis originates from mitochondria

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18
Q 
Cholesterol is synthesized from:
Select one: 
a. oxalate. 
b. malate.
c. lipoic acid. 
d. choline.
e. acetyl-CoA.
A

acetyl-CoA.

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19
Q

Where is acyl-CoA cholesterol-transferase (ACAT) localized?
Select one:

a. endoplasmic reticulum membrane
b. cytosol
c. mitochondrium matrix
d. inner mitochondrial membrane

A

a. endoplasmic reticulum membrane

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20
Q

Where is the SREBP regulator domain localized if there is excess cholesterol in the cell?

Select one:

a. cytosol
b. endoplasmic reticulum
c. Golgi
d. nucleus

A

b. endoplasmic reticulum

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21
Q

Which protein of the SREBP-dependent signalling binds directly cholesterol?

Select one:

a. SCAP
b. SREBP
c. INSIG
d. SREBP-cleavage protease

A

SCAP

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22
Q

What is the consequence of increased release of PCSK9?

Select one:

a. enhanced LDL uptake in hepatocytes
b. increased number of LDL receptors in hepatocytes
c. lower blood plasma LDL level
d. higher blood plasma LDL level

A

higher blood plasma LDL level

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23
Q

What is the consequence of enhanced IDOL production in the liver?

Select one:

a. enhanced LDL uptake in the liver
b. higher number of LDL-receptors in the hepatocytes
c. higher blood plasma LDL level
d. lower blood plasma LDL level

A

higher blood plasma LDL level

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24
Q

What is the function of the cholesteryl ester transfer protein (CETP)?

Select one:

a. transfers cholesteryl esters from extrahepatic cells to HDL
b. transfers cholesteryl esters from HDL to VLDL
c. transfers cholesteryl esters from the intestine to HDL
d. transfers cholesteryl esters from HDL to the liver

A

b. transfers cholesteryl esters from HDL to VLDL

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25
Q

What is the function of scavenger receptor B1 (SR-B1)?

Select one:

a. LDL endocytosis
b. HDL endocytosis
c. selective uptake of LDL-cholesterol
d. selective uptake of HDL-cholesterol

A

d. selective uptake of HDL-cholesterol

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26
Q

What chemical changes occur when primary bile acids are converted to secondary bile acids?

Select one:

a. removal of carboxylic groups
b. reduction of the double bond at 3C
c. removal of the 3C-hydroxylic group
d. removal of the 7C-hydroxylic group

A

removal of the 7C-hydroxylic group

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27
Q

Which value approaches most closely the daily rate of cholesterol synthesis in the liver (X) and in the extrahepatic tissues (Y) in adults (70 kg body weight)? Numbers are in mg cholesterol synthesized per kg organ mass.

Select one:

a. X=10; Y=1000
b. X=100; Y=100
c. X=250; Y=10
d. X=500; Y=1
e. X=1000; Y=0

A

c. X=250; Y=10

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28
Q

Which proteins are needed for the transfer of dietary cholesterol to extrahepatic tissues?

Select one or more:

a. apoB48
b. apoB100
c. lipoprotein lipase
d. acyl-CoA cholesterol acyl transferase e. lecithin cholesterol acyl transferase

A

b. apoB100
c. lipoprotein lipase
d. acyl-CoA cholesterol acyl transferase e. lecithin cholesterol acyl transferase

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29
Q

Which statements are true concerning proprotein convertase subtilisin- like/kexin type 9 (PCSK9)?

Select one or more:

a. it contributes to the intracellular processing of LDL receptors prior their exposure in the membrane
b. it stimulates the degradation of LDL receptors
c. it triggers the endocytosis of LDL-receptor
d. it binds to LDL receptors
e. it is a protease that degrades LDL receptors

A

b. it stimulates the degradation of LDL receptors
c. it triggers the endocytosis of LDL-receptor
d. it binds to LDL receptors

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30
Q

Which statements are true concerning Idol (inducer of degradation of LDL receptor)?

Select one or more:

a. it is a transcription factor controlling PCSK9 (proprotein convertase subtilisin-like/kexin type 9)
b. it is a protease that degrades LDL receptor
c. it binds LDL receptors extracellularly
d. it is under the control of LXR (liver X receptor)
e. it stimulates the ubiquitination of LDL receptor

A

b. it is a protease that degrades LDL receptor

e. it stimulates the ubiquitination of LDL receptor

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31
Q

Which statements are true concerning FXR (farnesoid X receptor)?

Select one or more:

a. it operates in fibroblasts, hepatocytes and intestinal epithelial cells
b. its ligands are bile acids
c. in fibroblasts it induces FGF19 (fibroblast growth factor 19)
d. in hepatocytes it induces 7a-hydoxylase
e. in intestinal epithelial cells it induces IBAT (ileal bile acid transporter)

A

b. its ligands are bile acids

e. in intestinal epithelial cells it induces IBAT (ileal bile acid transporter)

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32
Q

Which statements are true concerning miR-33 microRNA?

Select one or more:

a. its level increases in cholesterol depletion
b. its level increases in cholesterol overload
c. it stimulates the translation of ABCA1 (ATP binding cassette A 1 transporter)
d. it stimulates the transcription of NPC1 (Nieman-Pick type C 1 protein)
e. it suppresses the translation of ABCA1 (ATP binding cassette A 1 transporter)

A

a. its level increases in cholesterol depletion

e. it suppresses the translation of ABCA1 (ATP binding cassette A 1 transporter)

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33
Q

Select the factors that cause increase of the plasma LDL-cholesterol level

Select one or more:

a. LDL-receptor deficiency
b. Apo-B100 deficiency
c. lipoprotein lipase deficiency
d. PCSK9 (proprotein convertase subtilisin-like/kexin type 9) deficiency
e. Idol (inducer of degradation of LDL receptor) deficiency

A

a. LDL-receptor deficiency

b. Apo-B100 deficiency

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34
Q

What is the biological role of bile acids?

Select one or more:

a. they contribute to the interfacial activation of pancreatic lipase in the intestine
b. their micelles are essential for cholesterol absorption in the intestine c. they are ligands of FXR (farnesoid X receptor)
d. their micelles are essential for cholesterol disposal in the intestine
e. they are ligands of LXR (liver X receptor)

A

Except for ‘they are ligand of LXR’ all correct

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35
Q

Which reactions participate in the bile acid synthesis?

Select one or more:

a. 7alfa hydroxylation
b. 7beta hydroxylation
c. 12alfa hydroxylation
d. glycine conjugation
e. glutamine conjugation

A

a. 7alfa hydroxylation
c. 12alfa hydroxylation
d. glycine conjugation

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36
Q

What is the recommended daily allowance of cholesterol in normal mixed- type diet of adults?

Select one:

a. 0.5 g
b. 1 g
c. 2 g
d. 10 g
e. 100 g

A

a. 0.5 g

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37
Q

In what form are the C-atoms of cholesterol released from the human body?
Select one or more:

a. CO2
b. free cholesterol
c. cholesteryl esters
d. cholate
e. bilirubin

A

a. CO2
b. free cholesterol
d. cholate

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38
Q

In what form is cholesterol released by the liver?

Select one:

a. chylomicron
b. VLDL
c. LDL
d. IDL
e. in complex with albumin

A

b. VLDL

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39
Q

In what form is cholesterol taken up by the liver?
Select one or more:

a. chylomicron
b. chylomicron remnant
c. HDL
d. LDL
e. VLDL

A

b. chylomicron remnant
c. HDL
d. LDL

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40
Q

Select the correct order of enzymes or transporters operating in the disposal of excess cholesterol from the human body

Select one:

a. ABCA1 / LCAT / LDL / IDL / BSEP
b. ABCA1 / LCAT / LDL / VLDL / BSEP
c. ACAT / ABCA1 / HDL / LDL / BSEP
d. ABCA1 / LCAT / HDL / CETP / LDL
e. ABCA1 / ACAT / LCAT / HDL / LDL

A

d. ABCA1 / LCAT / HDL / CETP / LDL
(1. ABCA1 pumps cholesterol out of the cells using ATP
2. Loading of HDL with cholesterol
- > Cholesterol esterification on HDL: LCAT
3. 3. CETP: Cholesteryl-Ester-Transfer Protein
4. 4. Uptake of cholesterol in the liver)

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41
Q

Which cells express FXR?
Select one or more:

a. hepatocytes
b. enterocytes
c. macrophages
d. adipocytes
e. smooth muscle cells

A

a. hepatocytes

b. enterocytes

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42
Q

Which cells express LXR?
Select one or more:

a. hepatocytes
b. enterocytes
c. macrophages
d. adipocytes
e. smooth muscle cells

A

a. hepatocytes
b. enterocytes
c. macrophages
d. adipocytes
e. smooth muscle cells

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43
Q

Which statements are true regarding the lecithin cholesterol acyl transferase?
Select one or more:

a. It is one of the enzymes of cholesterol synthesis.
b. It forms cholesteryl esters.
c. It is localized in the membrane of the endoplasmic reticulum.
d. Apo AI is its activator.
e. It is active in phosphorylated state.

A

b. It forms cholesteryl esters.

d. Apo AI is its activator.

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44
Q

Which statements are true regarding the synthesis of cholesterol in mammalians?

Select one or more:

a. Cholesterol is synthesized only in the liver.
b. The rate of cholesterol synthesis is constant.
c. Cholesterol inhibits the activity of 3-hydroxy 3-methyl glutaryl-CoA reductase
d. Cholesterol inhibits the transcription of 3-hydroxy 3-methyl glutaryl-CoA reductase
e. Cholesterol inhibits the degradation of 3-hydroxy 3-methyl glutaryl-CoA reductase

A

c. Cholesterol inhibits the activity of 3-hydroxy 3-methyl glutaryl-CoA reductase
d. Cholesterol inhibits the transcription of 3-hydroxy 3-methyl glutaryl-CoA reductase

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45
Q

Which metabolic pathway uses the reaction catalyzed by 3-hydroxy 3-methyl glutaryl-CoA reductase?

Select one:

a. glycolysis
b. synthesis of ketone bodies
c. oxidation of fatty acids
d. synthesis of fatty acids
e. synthesis of cholesterol

A

e. synthesis of cholesterol

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46
Q

Where is the 3-hydroxy 3-methyl glutaryl-CoA reductase localized within the cell?

Select one:

a. cytosol
b. membrane of the endoplasmic reticulum
c. matrix of mitochondria
d. the inner membrane of mitochondria
e. the outer membrane of mitochondria

A

b. membrane of the endoplasmic reticulum

47
Q

Which of the following enzyme is not the component of the reagent for triglyceride determination?

Select one:

a. Peroxidase
b. Glycerol kinase
c. ACAT
d. Glycerol-3-phosphate oxidase
e. Lipoprotein lipase

A

c. ACAT

48
Q

Select the correct statement from the sentences below:

Select one:

a. Higher HDL-cholesterol level is accompanied with higher risk for myocardial infarct.
b. The determination of HDL-cholesterol is important for patients who have hypercholesterolemia
c. Cholesterol is only present in LDL and HDL liporpoteins.
d. Hyperlipoproteinaemia is protective against cardiovascular diseases.
e. Dyslipidaemia is an essential risk factor in bone diasesas.

A

b. The determination of HDL-cholesterol is important for patients who have hypercholesterolemia

(The lower the HDL-cholesterol level the higher is the risk of myocardial infarction. The determination of HDL-cholesterol is important for patients who have hypercholesterolemia, as well as hypertriglyceridemia. Simultaneously elevated levels of serum triglycerides and decreased levels of HDL-cholesterol indicate high coronary risk.)

49
Q

Which of the following enzymes is present in the reagent for cholesterol determination?

Select one:

a. Cholesterol esterase
b. HMG-CoA-reductase
c. LCAT
d. Glycerol-3-phosphate oxidase
e. Malate-dehydrogenase

A

a. Cholesterol esterase

(Cholesterol esters will be hydrolyzed by cholesterol esterase.
Cholesterol will be oxidized into cholest-4-en-3-on and H2O2 by bacterial cholesterol oxidase.
H2O2 in the presence of phenol and amino-4- antipyrine forms a complex of red color showing absorption maximum between 505 nm.)

50
Q

Select the correct statement for the determination of serum cholesterol!
Select one:

a. LDL-cholesterol level is determinded directly from the plasma-supernatant after precipitation of other lipoproteins.
b. HDL-cholesterol level is determinded directly from the plasma-supernatant after precipitation of other lipoproteins.
c. In the first step of cholesterol level determination, cholesterol-esthers will be hydrolised by cholesterol peroxidase.
d. VLDL-cholesterol level is determinded directly from the plasma- supernatant after precipitation of other lipoproteins.
e. Cholesterol determination is performed by the Biuret-reaction.

A

b. HDL-cholesterol level is determinded directly from the plasma-supernatant after precipitation of other lipoproteins.

(Separation of HDL fraction
HDL fraction will be separated from the other lipoproteins, which are precipitated in the presence of phosphotungstic acid-MgCl2. After the centrifugation, cholesterol content of the supernatants will be determined according to the method
described above for the total cholesterol content.)

51
Q

Which statement is false?

Select one:

a. Enzymatic hydrolysis of cholesteryl esters is needed for determination of HDL-cholesterol.
b. Determination of HDL-cholesterol is needed for determination of LDL- cholesterol.
c. Determination of HDL-cholesterol is needed for determination of total serum cholesterol.
d. Determination of serum triglyceride is needed for determination of LDL- cholesterol.
e. Precipitation and sedimentation of VLDL and LDL is needed for determination of HDL-cholesterol.

A

c. Determination of HDL-cholesterol is needed for determination of total serum cholesterol.

52
Q

Which statement is false?
The enzymatic reactions involved in determination of LDL-cholesterol include:

Select one:

a. hydrolysis of cholesteryl esters by cholesteryl esterase
b. hydrolysis of cholesteryl esters by cholesteryl esterase
c. oxidation of cholesterol by cholesterol oxidase
d. oxidation of glycerol by glycerol oxidase
e. reduction of hydrogen peroxide by peroxidase

A

d. oxidation of glycerol by glycerol oxidase

53
Q

Which statement is false?
Enzymatic determination of serum cholesterol and serum triglyceride both involve:

Select one:

a. hydrolysis of ester bonds
b. phosphorylation on the expense of ATP
c. oxidation by molecular oxygen
d. production of hydrogen peroxide
e. oxidation by hydrogen peroxide

A

b. phosphorylation on the expense of ATP

54
Q

Which statement is true?
Enzymatic determination of serum triglyceride does but determination of serum cholesterol does not involve:

Select one:

a. phosphorylation on the expense of ATP
b. hydrolysis of ester bonds
c. oxidation by molecular oxygen
d. dehydrogenation by using NAD+
e. oxidation by hydrogen peroxide

A

phosphorylation on the expense of ATP

55
Q

Which statement is true regarding the enzymatic determination of serum lipids?

Select one:
a. The assay procedure starts with precipitation of chylomicrons by trichloroacetic acid (TCA).

b. Lipoprotein lipase is needed to liberate fatty acids and cholesterol from the lipoproteins.
c. Both HDL-cholesterol and LDL-cholesterol are directly determined in different serum fractions.
d. LDL-cholesterol content is estimated as one fifth of the total serum triglyceride.
e. HDL-cholesterol can be determined in blood serum supernatant after precipitation and sedimentation of VLDL and LDL.

A

e. HDL-cholesterol can be determined in blood serum supernatant after precipitation and sedimentation of VLDL and LDL.

56
Q

Which statement is correct?

Select one:

a. the pancreatic lipase does not need a cofactor for its activity
b. the pancreatic lipase is proteolytically activated in the duodenum
c. bile acids and co-lipase are necessary for the interfacial activation of pancreatic lipase in the duodenum
d. co-lipase is a serine protease, which proteolytically activates pancreatic lipase in the duodenum
e. co-lipase alone can emulsify triglycerides in the duodenum

A

c. bile acids and co-lipase are necessary for the interfacial activation of pancreatic lipase in the duodenum

57
Q

Select the correct statements
Select one or more:

a. The acyl-CoA dehydrogenase is a mitochondrial enzyme
b. NAD is the coenzyme of acyl-CoA dehydrogenase
c. The acyl-CoA dehydrogenase generates a trans-double bond
d. No ketone bodies are produced, if the acyl-CoA dehydrogenase is deficient

A

a. The acyl-CoA dehydrogenase is a mitochondrial enzyme
c. The acyl-CoA dehydrogenase generates a trans-double bond (trans-delta2-enoyl-CoA)
d. No ketone bodies are produced, if the acyl-CoA dehydrogenase is deficient

58
Q

Select the statements valid for the ketone bodies

Select one or more:

a. Produced in the liver
b. Non-soluble in water
c. Only organs expressing the ß-ketoacyl-CoA-transferase enzyme can utilize them
d. Their amount increases in parallel with the increase of b-oxidation of fatty acids in the liver
e. They are not produced under physiological conditions

A

a. Produced in the liver
c. Only organs expressing the ß-ketoacyl-CoA-transferase enzyme can utilize them
d. Their amount increases in parallel with the increase of b-oxidation of fatty acids in the liver

59
Q

Select the statements valid for the synthesis of fatty acids

Select one or more:

a. The activity of acetyl-CoA carboxilase primarily determines the overall rate of the process
b. The acetyl-CoA is transported in the form of citrate to the site of synthesis
c. NADH2 is utilized in the reactions of the process
d. The ATP-citrate-lyase provides the immediate precursor of the synthesis
e. The carnitine carrier is involved in the process

A

a. The activity of acetyl-CoA carboxilase primarily determines the overall rate of the process
b. The acetyl-CoA is transported in the form of citrate to the site of synthesis
d. The ATP-citrate-lyase provides the immediate precursor of the synthesis

60
Q

Select the statements valid for the synthesis of palmitoic acid

Select one or more:

a. The fatty acid synthase is a cytoplasmic enzyme
b. The elongation of the molecule by two carbon atoms is accompanied by the oxidation of two NADPH
c. The fatty acyl-group is attached to ACP in the course of the synthesis
d. Malonyl-CoA loses a carboxyl group during the process
e. Acetyl CoA binds to a SH-group of the condensing enzyme

A

All are correct

61
Q

The amount of which enzymes increases following a carbohydrate-rich meal

Select one or more:

a. Acetyl-CoA carboxylase
b. Fatty acid synthase
c. ATP-citrate lyase
d. glucose-6-phosphate dehydrogenase
e. malic enzyme

A

All of them

62
Q

Select the statements valid for the synthesis of triacylglycerols (TAG)

Select one or more:

a. In adipose tissue the glycerol-kinase provides the glycerol-3-phosphate for the TAG synthesis
b. One of the intermediates of the synthesis in the liver is the phosphatidate
c. One of the intermediates of the synthesis in the intestine is the 2- monoacylglycerol
d. The TAG synthesized in the adipose tissue is transported to other tissues by VLDL
e. The absorption of TAG in the intestine involves synthesis of TAG in the epithelial cells

A

b. One of the intermediates of the synthesis in the liver is the phosphatidate
c. One of the intermediates of the synthesis in the intestine is the 2- monoacylglycerol
e. The absorption of TAG in the intestine involves synthesis of TAG in the epithelial cells

63
Q

Select the statements valid for the metabolism of fatty acids with odd number of carbon atoms

Select one or more:

a. Acetyl-CoA is formed in the course of oxidation
b. Propionyl-CoA is formed in the course of oxidation
c. Biotin is required
d. Succinyl-CoA is formed in the course of oxidation
e. Vitamin B12 is required

A

All of them

64
Q

Select the coenzymes needed for the b-oxidation of fatty acids

Select one or more:

a. CoA
b. NADP
c. FAD
d. NAD
e. thiamine-PP

A

a. CoA
c. FAD
d. NAD

65
Q

Select the coenzyme needed for both b-oxidation and synthesis of fatty acids

a. Biotin
b. CoA
c. FAD
d. NAD
e. NADP

A

b. CoA

66
Q

Select the coenzymes needed for the synthesis of fatty acids
Select one or more:

a. CoA
b. NADP
c. FAD
d. NAD
e. biotin

A

a. CoA
b. NADP
e. biotin

67
Q

Select the compounds, which are not classified as ketone bodies
Select one or more:

a. Dihydroxyacetone
b. Acetoacetate
c. b-hydroxybutyrate
d. a-hydroxybutyrate
e. oxaloacetate

A

a. Dihydroxyacetone

d. a-hydroxybutyrate

68
Q

The conversion of palmitoyl-CoA (16:0) to myristoyl-CoA (14:0) and 1 mol of acetyl-CoA by the beta-oxidation pathway results in the net formation of:

Select one:

a. 2 FADH2, 2 NADH, and 1 ATP.
b. 2 FADH2 and 2 NADH.
c. 1 FADH2, 1 NADH, and 1 ATP.
d. 1 FADH2 and 1 NADPH.
e. 1 FADH2 and 1 NADH.

A

e. 1 FADH2 and 1 NADH.

69
Q

The following statements are valid for the beta-oxidation of saturated fatty acids with even number of C-atoms:
Select one or more:

a. localized to the cytosol
b. fatty acids must be activated by ketothiolase using ATP
c. Malonyl-CoA is an allosteric regulator
d. oxidation of 1 mol palmitoic acid to CO2 and water covers the synthesis of 106 mol ATP
e. requires vitamin B12 cofactor

A

c. Malonyl-CoA is an allosteric regulator

d. oxidation of 1 mol palmitoic acid to CO2 and water covers the synthesis of 106 mol ATP

70
Q

The rate of fatty acid synthesis is increased by
Select one or more:

a. insulin
b. long-chain fatty acids
c. NADH
d. glucagon
e. citrate

A

a. insulin

e. citrate

71
Q

Which factors participate in intestinal lipid digestion?

Select one:

a. Lipase and ATP
b. Lipase, bile acid and CoA
c. Lipoprotein lipase and bile acids
d. Mucins and phospholipids
e. Pancreatic lipase and bile acids

A

e. Pancreatic lipase and bile acids

72
Q

What is the mechanism of fatty acid activation?

Select one:

a. a reaction requiring free CoA and ATP
b. binding to carnitine
c. formation of UDP-acids
d. phosphorylation with ATP
e. transfer of CoA from malonyl CoA

A

a reaction requiring free CoA and ATP

73
Q

Which molecule is needed for the transport of fatty acids into the mitochondria?

Select one: 
a. Cardiolipin
 b. Carnitine 
c. Carnosine 
d. Creatine e
. Glycine
A

b. Carnitine

74
Q

Which enzymes participate in the metabolism of ketone bodies?
Select one or more:
a. ATP-citrate-lyase
b. HMG-CoA-lyase
c. HMG-CoA -synthase
d. HMG-CoA-reductase
e. Succinyl-CoA-acetoacetate CoA transferase

A

b. HMG-CoA-lyase
c. HMG-CoA -synthase
e. Succinyl-CoA-acetoacetate CoA transferase

75
Q

Transport of fatty acids from the cytoplasm to the mitochondrial matrix requires:

Select one:

a. ATP, carnitine, and coenzyme A.
b. ATP, carnitine, and pyruvate dehydrogenase.
c. ATP, coenzyme A, and hexokinase.
d. ATP, coenzyme A, and pyruvate dehydrogenase.
e. carnitine, coenzyme A, and hexokinase.

A

a. ATP, carnitine, and coenzyme A.

76
Q

Fatty acids are activated to acyl-CoAs and the acyl group is further transferred to carnitine because:

Select one:

a. Acyl-carnitines are transported across the mitochondrial membrane, but acyl-CoAs do not.
b. acyl-CoAs easily cross the mitochondrial membrane, but the fatty acids themselves will not.
c. Carnitine is required to oxidize NAD+ to NADH.
d. Fatty acids cannot be oxidized by FAD unless they are in the acyl-carnitine form.
e. None of the above is true.

A

a. Acyl-carnitines are transported across the mitochondrial membrane, but acyl-CoAs do not.

77
Q

Carnitine is:

Select one:

a. a 15-carbon fatty acid.
b. an essential cofactor for the citric acid cycle.
c. essential for intracellular transport of fatty acids.
d. one of the amino acids commonly found in protein.
e. present only in carnivorous animals.

A

c. essential for intracellular transport of fatty acids.

78
Q

Which of these is able to cross the inner mitochondrial membrane?

Select one:

a. acetyl-CoA
b. fatty acyl-carnitine
c. fatty acyl-CoA
d. malonyl-CoA
e. None of the above can cross.

A

d. malonyl-CoA

79
Q

Saturated fatty acids are degraded two carbons at a time, producing acetyl- CoA. Under aerobic conditions, how many ATP molecules would be produced per acetyl-CoA formed?

Select one:

a. 2
b. 3
c. 4
d. 5
e. 6

A

c. 4

80
Q

Which of the following is(are) true of the oxidation of 1 mol of palmitate (a 16- carbon saturated fatty acid; 16:0) by the beta-oxidation pathway, beginning with the free fatty acid in the cytoplasm?

Select one or more:

a. Activation of the free fatty acid requires the equivalent of two ATPs.
b. Inorganic pyrophosphate (PPi) is produced.
c. Carnitine functions as an electron acceptor.
d. 8 mol of FADH2 are formed.
e. 8 mol of acetyl-CoA are formed.
f. There is no direct involvement of NAD+.

A

a. Activation of the free fatty acid requires the equivalent of two ATPs.
b. Inorganic pyrophosphate (PPi) is produced.
e. 8 mol of acetyl-CoA are formed.

81
Q

Which of the following statements apply (applies) to the beta-oxidation of fatty acids?

Select one or more:

a. The process takes place in the cytosol of mammalian cells.
b. Carbon atoms are removed from the acyl chain one at a time.
c. Before oxidation, fatty acids must be converted to their CoA derivatives.
d. NADP+ is the electron acceptor.
e. The products of beta-oxidation can directly enter the citric acid cycle for further oxidation.

A

c. Before oxidation, fatty acids must be converted to their CoA derivatives.
e. The products of beta-oxidation can directly enter the citric acid cycle for further oxidation.

82
Q

Which of the following is not true regarding the oxidation of 1 mol of palmitate (16:0) by the beta-oxidation pathway?

Select one:

a. ATP is needed.
b. 8 mol of acetyl-CoA are formed.
c. AMP and PPi are formed.
d. 8 mol of FADH2 are formed.
e. The reactions occur in the mitochondria.

A

d. 8 mol of FADH2 are formed.

83
Q

Which compound is an intermediate of the ß-oxidation of fatty acids?

a. CH3–CH2–CO–CH2–OH
b. CH3–CH2–CO–CH2–CO–OPO32-
c. CH3– (CH2)20–CO–COOH
d. CH3–CH2–CO–CO–S–CoA
e. CH3–CO–CH2–CO–S—CoA

A

e. CH3–CO–CH2–CO–S—CoA

84
Q

Which of the following statements concerning the ß-oxidation of fatty acids is true?

Select one:

a. About 1,200 ATP molecules are ultimately produced per 20-carbon fatty acid oxidized.
b. The free fatty acid must be carboxylated in the beta position by a biotin- dependent reaction before the process of beta-oxidation commences.
c. Two NADH are produced for each acetyl-CoA.
d. The free fatty acid must be converted to a thioester before the process of ß-oxidation commences.

A

d. The free fatty acid must be converted to a thioester before the process of ß-oxidation commences.

85
Q

Which of the following is /are true of the ß-oxidation of long-chain fatty acids?

Select one or more:

a. The enzyme complex that catalyzes the reaction contains biotin.
b. FADH2 serves as an electron carrier.
c. NADH serves as an electron carrier.
d. Oxidation of an 18-carbon fatty acid produces six molecules of propionyl- CoA.
e. Oxidation of a 15-carbon fatty acid produces at least one propionyl-CoA.

A

b. FADH2 serves as an electron carrier.
c. NADH serves as an electron carrier.
e. Oxidation of a 15-carbon fatty acid produces at least one propionyl-CoA.

86
Q

The following fatty acid, in which the indicated carbon is labeled with 14C, is fed to an animal: 14CH3(CH2)9COOH
After allowing 30 minutes for fatty acid ß-oxidation, the label would most likely be recovered in:

Select one:

a. acetyl-CoA.
b. both acetyl-CoA and propionyl-CoA.
c. palmitoyl-CoA.
d. propionyl-CoA.

A

d. propionyl-CoA.

87
Q

A fatty acid with an odd number of carbons will enter the citric acid cycle as acetyl-CoA and:

Select one:

a. butyrate.
b. citrate.
c. malate.
d. succinyl-CoA.
e. a-ketoglutarate.

A

d. succinyl-CoA.

88
Q

In the disease sprue, vitamin B12 (cobalamin) is poorly absorbed in the intestine, resulting in vitamin B12 deficiency. If each of the following fatty acids were in the diet, for which one would the process of fatty acid oxidation be most affected in a patient with sprue?

Select one:

a. CH3(CH2)14COOH
b. CH3(CH2)12COOH
c. CH3(CH2)11COOH
d. CH3(CH2)10COOH

A

d. CH3(CH2)10COOH (odd number of C atoms)

89
Q

The major site of formation of acetoacetate from fatty acids is the:

Select one:

a. Adipose tissue.
b. Intestinal mucosa.
c. Kidney.
d. Liver.
e. Muscle.

A

d. Liver.

90
Q

Which of the following is not specifically required in the synthesis of fatty acids?

Select one:

a. acetyl-CoA
b. biotin
c. HCO3- (CO2)
d. malonyl-CoA
e. NADH

A

e. NADH

91
Q

Which of the following statements is /are true regarding the synthesis of fatty acids ?

Select one:

a. Acyl intermediates are thioesters of a low molecular weight protein called acyl carrier protein.
b. CO2 or HCO3- is essential.
c. The ultimate source of all the carbon atoms in the fatty acid product is acetyl-CoA.
d. All of the above are true.

A

d. All of the above are true.

92
Q

Which of the following is not true of the reaction in which malonyl-CoA is produced during fatty acid synthesis?

Select one:

a. It is stimulated by citrate.
b. It requires acyl carrier protein (ACP).
c. It requires CO2 (or bicarbonate).
d. The cofactor is biotin.

A

b. It requires acyl carrier protein (ACP).

(FA synthase)

93
Q

If malonyl-CoA is synthesized from radioactive (14C-labeled) carbon dioxide and unlabeled acetyl-CoA, and the labeled malonate is then used for fatty acid synthesis, the final product (fatty acid) will have radioactive carbon in:

Select one:

a. Every C.
b. Every even-numbered C.
c. Every odd-numbered C (carboxyl end is C-1).
d. No part of the molecule.
e. Only the farthest carbon from C-1.

A

d. No part of the molecule. (all C atoms coming from Acetyl CoA)

94
Q

In comparing fatty acid biosynthesis with ß-oxidation of fatty acids, which of the following statements is incorrect?

Select one:

a. A thioester derivative of crotonic acid (trans-2-butenoic acid) is an intermediate in the synthetic path, but not in the degradative path.
b. A thioester derivative of D-ß-hydroxybutyrate is an intermediate in the synthetic path, not in the degradative path.
c. Fatty acid biosynthesis uses NADPH exclusively, whereas ß-oxidation uses NAD+ exclusively.
d. Fatty acid degradation is catalyzed by cytosolic enzymes; fatty acid synthesis by mitochondrial enzymes.
e. The condensation of two moles of acetyl-CoA in the presence of a crude extract is more rapid in bicarbonate buffer than in phosphate buffer at the same pH; the cleavage of acetoacetyl-CoA proceeds equally well in either buffer.

A

d. Fatty acid degradation is catalyzed by cytosolic enzymes; fatty acid synthesis by mitochondrial enzymes.

95
Q

Which of the following is not true of both the fatty acid synthase system and the fatty acid ß-oxidation system?

Select one:

a. A derivative of the vitamin pantothenic acid is involved.
b. Acyl-CoA derivatives are intermediates.
c. Double bonds are oxidized or reduced by pyridine nucleotide coenzymes.
d. The processes occur in the mitochondrial matrix.

A

d. The processes occur in the mitochondrial matrix.

96
Q

Enzymes that catalyze the synthesis of long chain fatty acids in vertebrate cells:

Select one:

a. act as seven separate proteins.
b. are encoded in mitochondrial genes.
c. are localized in the mitochondrial matrix.
d. are part of a single polypeptide chain containing several distinct enzyme activities.
e. have none of the characteristics above.

A

d. are part of a single polypeptide chain containing several distinct enzyme activities.

97
Q

The rate-limiting step in fatty acid synthesis is:
Select one:
a. condensation of acetyl-CoA and malonyl-CoA.
b. formation of acetyl-CoA from acetate.
c. formation of malonyl-CoA from malonate and coenzyme A.
d. the reaction catalyzed by acetyl-CoA carboxylase.
e. the reduction of the acetoacetyl group to a ß-hydroxybutyryl group.

A

d. the reaction catalyzed by acetyl-CoA carboxylase.

98
Q

Which of the following is not true of the fatty acid elongation system of vertebrate cells?

Select one:

a. It involves the same four-step sequence seen in the fatty acid synthase complex.
b. It is located in the smooth endoplasmic reticulum.
c. It produces stearoyl-CoA by the extension of palmitoyl-CoA.
d. It uses malonyl-CoA as a substrate.
e. The immediate precursor of the added carbons is acetyl-CoA.

A

e. The immediate precursor of the added carbons is acetyl-CoA.

99
Q

The enzyme system for adding double bonds to saturated fatty acids requires all of the following except:

Select one:

a. A mixed-function oxidase.
b. ATP.
c. Cytochrome b5.
d. Molecular oxygen (O2).
e. NADPH.

A

b. ATP.

100
Q

Which of the following statements is NOT valid for the lipoprotein lipase ?

a. An isoenzyme with a low KM is present in the mammary gland b. It degrades the majority of plasma triacylglycerols
c. It is bound to the luminal surface of the capillary endothelial cells
d. Its activity increases in the fasting state
e. VLDL carries its cofactor

A

d. Its activity increases in the fasting state

101
Q

Select the correct statements

Select one or more:

a. The hormone-sensitive lipase (HSL) cleaves all three fatty acids from triacylglycerols (TAG)
b. Adipocytes express HSL
c. The phosphorylated form of HSL is inactive
d. The TAG-derived glycerol can not be phosphorylated in adipocytes
e. The liver and the intestine express glycerol kinase

A

b. Adipocytes express HSL
d. The TAG-derived glycerol can not be phosphorylated in adipocytes
e. The liver and the intestine express glycerol kinase

102
Q

Select the statements relevant to control mechanisms involved in the regulation of the plasma cholesterol level

Select one or more:

a. LDL-receptors are under transcriptional control based on SREBP
b. SREBP is released following cholesterol-dependent proteolysis of a precursor protein
c. SREBP is a nuclear receptor that binds sterols
d. LXR is a nuclear receptor that binds sterols
e. Cyp7a is under transcriptional control based on LXR
f. LXR prevents the release of cholesterol from the cells

A

a. LDL-receptors are under transcriptional control based on SREBP
b. SREBP is released following cholesterol-dependent proteolysis of a precursor protein
c. SREBP is a nuclear receptor that binds sterols
e. Cyp7a is under transcriptional control based on LXR

(The gene encoding cholesterol 7alpha-hydroxylase (CYP7A), the rate-limiting enzyme in bile acid synthesis, is transcriptionally regulated by bile acids and hormones. Previously, we have identified two bile acid response elements (BARE) in the promoter of the CYP7A gene
=> LXR - Oxysterols bind to 7-alpha-Hydroxylase → bile acid synthesis)

103
Q

Select the set of factors, in which the sequence of the list reflects most completely the major route of cholesterol stored in an extrahepatic tissue to its disposal in the intestine as bile salts

Select one or more:

a. LDL
b. HDL
c. cholesterylester transfer protein (CETP)
d. lipoprotein lipase
e. hepatic lipase
f. LDL-receptor
g. Cyp7a
h. ABCA1 transporter

A

a. LDL
b. HDL
c. cholesterylester transfer protein (CETP)
f. LDL-receptor
g. Cyp7a
h. ABCA1 transporter

104
Q

Which of the following statements is valid for the role of hypertriglyceridemia (HTG) in the initiation of atherosclerosis?

Select one:

a. HTG increases the shuttling of the cholesterylester transfer protein between HDL and VLDL with consequent formation of small dense LDL and loss of HDL.
b. HTG stimulates the uptake of triglycerides in the arterial endothelial cells with consequent conversion of fatty acids to cholesterol and its deposition in the arterial wall.
c. HTG results in overloading of LDL with triglycerides and the large LDL is a better (higher affinity) ligand of the scavenger receptors with consequent increased deposition of LDL in the arterial wall.
d. HTG results in overloading of HDL with triglycerides and the large HDL is transformed from anti-atherogenic to pro-atherogenic lipoprotein, which easily precipitates in the arterial wall.
e. The VLDL with high triglyceride content is a better ligand of the LDL- receptor than the LDL and thus much more cholesterol is taken up by the macrophages in the arterial wall.

A

a. HTG increases the shuttling of the cholesterylester transfer protein between HDL and VLDL with consequent formation of small dense LDL and loss of HDL.

105
Q

Select the statements valid for the scavenger receptors (SR).

Select one or more:

a. SRs are alternative specific receptors for the uptake of LDL.
b. Following binding of LDL to SRA the ligand-receptor complex is internalized.
c. SRBI is the major receptor for the uptake of oxidized LDL in macrophages.
d. SRA is under cholesterol-dependent transcriptional control.
e. SRBI participates in the uptake of HDL-cholesterol in the liver.

A

b. Following binding of LDL to SRA the ligand-receptor complex is internalized.
e. SRBI participates in the uptake of HDL-cholesterol in the liver.
(he high density lipoprotein (HDL) receptor, scavenger receptor class B, type I (SR-BI), mediates selective cholesteryl ester uptake from lipoproteins )

( as HDL2 : hepatic lipase and SR-B1 (scavenger receptor B1) cooperate: discoid HDL is regenerated – can start a new round)

106
Q

Lipoprotein lipase hydrolyzes triacylglycerols of the following lipoproteins:

Select one or more:

a. VLDL
b. nascent chylomicron
c. mature chylomicron
d. chylomicron remnant
e. HDL3

A

a. VLDL

b. nascent chylomicron

107
Q

Which lipoprotein carries cholesterol to the extrahepatic tissues?

Select one:

a. chylomicron
b. HDL
c. IDL
d. LDL
e. VLDL

A

d. LDL

108
Q

Which proteins participate in the reverse cholesterol transport?

Select one or more:

a. apoprotein A-I
b. LCAT
c. apoprotein B-48
d. apoprotein C-II
e. LPL

A

a. apoprotein A-I
b. LCAT

(Reverse cholesterol transport is a multi-step process resulting in the net movement of cholesterol from peripheral tissues back to the liver first via entering the lymphatic system, then the bloodstream. Cholesterol from non-hepatic peripheral tissues is transferred to HDL by the ABCA1)

109
Q

Which statements are valid in starvation?

Select one or more:

a. Lipoprotein lipase is activated in adipose tissue.
b. Triacylglycerols in chylomicrons are hydrolyzed
c. HDL level increases
d. Activity of hormone-sensitive lipase increases
e. Phosphatidate phosphohydrolase activity in liver decreases

A

d. Activity of hormone-sensitive lipase increases
e. Phosphatidate phosphohydrolase activity in liver decreases

(A is only for digestion and absorption of fat)

110
Q

Plasma level of unesterified fatty acids is increased:
Select one or more:

a. in starvation
b. in well-fed state
c. by glucagon
d. by ACTH
e. by insulin

A

a. in starvation c. by glucagon d. by ACTH

111
Q

Insulin participates in the regulation of lipolysis, because it …

Select one or more:

a. activates lipoprotein lipase in adipose tissue
b. promotes the phosphorylation of hormone-sensitive lipase
c. activates the phosphatase which dephosphorylates hormone-sensitive lipase
d. activates phosphodiesterase
e. inhibits adenylate cyclase

A

a. activates lipoprotein lipase in adipose tissue
c. activates the phosphatase which dephosphorylates hormone-sensitive lipase
d. activates phosphodiesterase

112
Q

Free fatty acids in the bloodstream are:
Select one:
a. bound to hemoglobin.
b. carried by the protein serum albumin.
c. freely soluble in the aqueous phase of the blood.
d. nonexistent; the blood does not contain free fatty acids. e. present at levels that are independent of epinephrine.

A

b. carried by the protein serum albumin.

113
Q

Lipoprotein lipase acts in:
Select one:
a. hydrolysis of triacylglycerols of plasma lipoproteins to supply fatty acids to various tissues.
b. intestinal uptake of dietary fat.
c. intracellular lipid breakdown of lipoproteins.
d. lipoprotein breakdown to supply needed amino acids.
e. none of the above.

A

a. hydrolysis of triacylglycerols of plasma lipoproteins to supply fatty acids to various tissues.

114
Q

The role of hormone-sensitive triacylglycerol lipase is to:

Select one:

a. hydrolyze lipids stored in the liver.
b. hydrolyze triacylglycerols stored in adipose tissue.
c. hydrolyze membrane phospholipids in hormone-producing cells.
d. synthesize triacylglycerols in the liver.
e. synthesize lipids in adipose tissue.

A

b. hydrolyze triacylglycerols stored in adipose tissue.

Biochemistry (Questions) (35 decks)

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