988 - 1084 Carbohydrate metabolism

Question 1

Which statement is false?

Select one:
a. Trypsin can cleave the peptide bond formed by the carboxyl group of a basic amino acid.
b. Trypsin can cleave the peptide bond formed by the amino group of a basic amino acid.
c. Chymotrypsin can cleave the peptide bond formed by the carboxyl group of aromatic amino acids.
d. Chymotrypsin can cleave the peptide bond near tyrosine.
e. Trypsin can cleave the peptide bond near lysine.

Answer 1

a. Trypsin can cleave the peptide bond formed by the carboxyl group of a basic amino acid.

Question 2

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

Answer 2

c. ACAT

Question 3

Select the correct statement from the sentences below:

Select one:
a. Higher HDL-cholesterol level is accompanied with higher risk for myocardial infarct.
b. Determination of LDL-cholesterol level is important for patients with familial and secondary hypercholesterinaemia.
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.

Answer 3

b. Determination of LDL-cholesterol level is important for patients with familial and secondary hypercholesterinaemia.

Question 4

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

Answer 4

a. Cholesterol esterase

Question 5

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.

Answer 5

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

Question 6

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.

Answer 6

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

Question 7

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.

Answer 7

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

Question 8

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

Answer 8

d. oxidation of glycerol by glycerol oxidase

Question 9

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

Answer 9

b. phosphorylation on the expense of ATP

Question 10

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

Answer 10

a. phosphorylation on the expense of ATP

Question 11

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.

Answer 11

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

Question 12

An uncoupler is:

Select one:
a. A lipophilic substance or a protein with the ability to transport protons across the inner mitochondrial membrane bypassing the Fo-F1 ATP synthase
b. An inhibitor of the Fo-F1 ATP synthase
c. An inhibitor of cytochrome c oxidase
d. An inhibitor of the adenine nucleotide translocase
e. A lipophilic substance or a protein with the ability to transport NADH across the inner mitochondrial membrane

Answer 12

a. A lipophilic substance or a protein with the ability to transport protons across the inner mitochondrial membrane bypassing the Fo-F1 ATP synthase

Question 13

Which statement is true regarding serine proteases?

Select one:
a. Serine proteases are proteases that have serine and tyrosine bonded at the active site.
b. The serine proteases are the enzymes that catalyze the hydrolysis of phosphoanhydryl bond.
c. The serine proteases are the enzymes that catalyze the hydrolysis of ester or amide bond.
d. Serine proteases are proteases that have serine and proline bonded at the active site.
e. Hydrolysis of amide bond involves the reaction of acylation of the carbroxyl group of Asp102.

Answer 13

c. The serine proteases are the enzymes that catalyze the hydrolysis of ester or amide bond.

Question 14

Which statement is false regarding serine proteases?

Select one:
a. Serine proteases are proteases that have serine bonded at the active site.
b. Serine proteases are the enzymes that catalyze the hydrolysis of ester or amide bond.
c. Catalytic triad of serine proteases located in the active site of the enzyme consist of three amino acids: His57, Ser195 and Asp102.
d. Many proteases are synthesized and secreted as inactive forms called zymogens and subsequently activated by proteolysis.
e. Catalytic triad of serine proteases located in the active site of the enzyme consist of three amino acids: Lys57, Ser195 and Tyr102.

Answer 14

e. Catalytic triad of serine proteases located in the active site of the enzyme consist of three amino acids: Lys57, Ser195 and Tyr102.

Question 15

Which statement is true regarding serine proteases?

Select one:
a. Chymotrypsin is synthesized as active enzyme.
b. Substrate binding pocket of chymotrypsin is more hydrophobic than in trypsin, therefore chymotrypsin prefers medium to large sized hydrophobic residues, such as tyrosine, phenylalanine and tryptophan in binding pocket.
c. Substrate binding pocket of chymotrypsin is less hydrophobic than in trypsin, therefore chymotrypsin prefers Arg or Lys in binding pocket.
d. Chymotrypsin cleave peptide bonds following a negatively charged amino acid serine or histidine.
e. Serine proteases are not sequence specific.

Answer 15

b. Substrate binding pocket of chymotrypsin is more hydrophobic than in trypsin, therefore chymotrypsin prefers medium to large sized hydrophobic residues, such as tyrosine, phenylalanine and tryptophan in binding pocket.

Question 16

Which statement is false regarding serine proteases?

Select one:
a. Bound substrate is attacked by acidophilic Asp195 of chymotripsinogen active site forming transition state complex (tetrahedral intermediate).
b. Serine proteases responsible for digestion can be categorised based on their substrate specificity as either chymotrypsin-like, trypsin-like or elastase- like.
c. Catalysis by serine proteases involves formation of a covalent acyl-enzyme intermediate.
d. Trypsin cleaves peptide bonds following a positively charged amino acid lysine or arginine.
e. Chymotrypsin is synthesized as inactive proenzymes (chymotrypsinogen) and activated subsequently by proteolysis.

Answer 16

a. Bound substrate is attacked by acidophilic Asp195 of chymotripsinogen active site forming transition state complex (tetrahedral intermediate).

Question 17

Which statement is false regarding serine proteases?

Select one:
a. Chymotrypsin is a digestive enzyme synthesized in its inactive form in the pancreas, along with the related enzymes trypsin and elastase belonging to the superfamily of serine proteases.
b. Chymotrypsin is transported to the small intestine in an inactive form. Once the enzyme enters the small intestine, it becomes activated by proteolysis.
c. Serine proteases are inhibited by natural inhibitors called “serpins”. One of the best-studied serpins are antithrombin and alpha 1-antitrypsin.
d. Activation of trypsin is autocatalytic.
e. Zymogens are active forms of serine proteases in which active sites are fully saturated by their substrates.

Answer 17

e. Zymogens are active forms of serine proteases in which active sites are fully saturated by their substrates.

Question 18

The effect of an uncoupler is:

Select one:
a. Dissipation of the proton motive force
b. Inhibition of respiration
c. Increase of mitochondrial ATP synthesis
d. Increase in protein transport to mitochondria
e. None of them

Answer 18

a. Dissipation of the proton motive force

Question 19

2,4-dinitrophenol is:

Select one:
a. An inhibitor of the Fo-F1 ATP synthase
b. An uncoupler
c. An inhibitor of cytochrome c oxidase
d. An inhibitor of the adenine nucleotide translocase
e. None of them

Answer 19

b. An uncoupler

Question 20

Atractyloside is:

Select one:
a. An inhibitor of the adenine nucleotide translocase
b. An inhibitor of the Fo-F1 ATP synthase
c. An inhibitor of cytochrome c oxidase
d. An uncoupler
e. None of them

Answer 20

a. An inhibitor of the adenine nucleotide translocase

Question 21

Respiratory control ratio is:

Select one:
a. The ratio of oxygen consumption of mitochondria in the presence of ADP and substrates divided by the oxygen consumption in the absence of ADP or substrates
b. The ratio of the amount of NADH transported across the inner mitochondrial membrane divided by the amount of oxygen consumed by mitochondria
c. The ratio of the amount of phosphate incorporated to ATP divided by the amount of oxygen consumed by mitochondria
d. The ratio of the amount of oxygen consumed by mitochondria divided by moles of H+ translocated across the inner mitochondrial membrane
e. None of them

Answer 21

a. The ratio of oxygen consumption of mitochondria in the presence of ADP and substrates divided by the oxygen consumption in the absence of ADP or substrates

Question 22

The P/O ratio is:

Select one:
a. The ratio of oxygen consumption of mitochondria in the presence of ADP and substrates divided by the rate of oxygen consumption in the absence of ADP or substrates
b. The ratio of the amount of NADH transported across the inner mitochondrial membrane divided by the amount of oxygen consumed by mitochondria
c. The ratio of the amount of phosphate incorporated to ATP divided by the amount of oxygen consumed by mitochondria
d. The ratio of the amount of oxygen consumed by mitochondria divided by moles of H+ translocated across the inner mitochondrial membrane
e. None of them

Answer 22

c. The ratio of the amount of phosphate incorporated to ATP divided by the amount of oxygen consumed by mitochondria

Question 23

Oligomycin is:

Select one:
a. An inhibitor of the adenine nucleotide translocase
b. An uncoupler
c. An inhibitor of complex I
d. An inhibitor of the Fo-F1 ATP synthase
e. An inhibitor of complex IV

Answer 23

d. An inhibitor of the Fo-F1 ATP synthase

Question 24

Inhibitors of complex IV are:

Select one:
a. Rotenone, antimycin
b. Oligomycin, atractyloside
c. Malonate, 2,4-dinitrophenol
d. CN-, CO, N3-
e. None of them

Answer 24

d. CN-, CO, N3-

Question 25

Mitochondrial succinate dehydrogenase is: Select one: a. an FMN-linked dehydrogenase b. an NADP+-linked dehydrogenase c. an FAD-linked dehydrogenase d. an NAD+-linked dehydrogenase e. a both NAD+ and NADP+-linked dehydrogenase

Answer 25

c. an FAD-linked dehydrogenase

Question 26

Which one of the following is a competitive inhibitor of succinate dehydrogenase? Select one: a. rotenone b. malonate c. alanine d. malate e. ATP

Answer 26

b. malonate

Question 27

Which one of the following statements describes the mechanism of action of malonate? Select one: a. Acts as an uncoupler b. Acts as inhibitor of ATP/ADP transporter c. Inactivates the ATP synthase complex d. Inactivates pyruvate kinase e. Acts as a competitive inhibitor of succcinate dehydrogenase

Answer 27

e. Acts as a competitive inhibitor of succcinate dehydrogenase

Question 28

Which one of the following statements describes the inhibition of succinate dehydrogenase by malonate? Select one: a. malonate decreases Km by interfering with the binding of the substrate b. malonate does not change Km, but decreases Vmax c. malonate can bind to the free E or to the ES complex as well d. malonate does not affect Vmax e. the inhibition by malonate can be enhanced by increasing the concentration of succinate

Answer 28

d. malonate does not affect Vmax

Question 29

Choose the correct answer: The reaction rate of succinate dehydrogenase was measured in the laboratory practice by detecting the following compound: Select one: a. NADH b. oxidized form of iodonitrotetrazolium chloride c. FADH2 d. reduced iodonitrotetrazolium formazan e. amino-4-antipyrine

Answer 29

d. reduced iodonitrotetrazolium formazan

Question 30

Which statement is true regarding the inhibition of succinate dehydrogenase by malonate? Select one: a. malonate binds irreversibly to the active site of the enzyme b. malonate binds reversibly to the active site of the enzyme and therefore not only ES complexes but EI complexes will also be formed c. Km is decreased in the presence of malonate d. vmax is decreased in the presence of malonate e. both the Km and vmax are decreased in the presence of malonate

Answer 30

b. malonate binds reversibly to the active site of the enzyme and therefore not only ES complexes but EI complexes will also be formed

Question 31

We characterized the competitive inhibition of succinate dehydrogenase by malonate in the laboratory practice by plotting the results on a graph. Which one of the following statements is true? Select one: a. we plotted malonate concentration versus succinate concentration b. we plotted 1/v versus 1/[S] c. the intercept on the Y axis of the graph gave the -1/KM d. the intercept on the X axis of the graph gave the 1/vmax e. we plotted the reaction rate versus 1/[S]

Answer 31

b. we plotted 1/v versus 1/[S]

Question 32

Which one of the following parameters did we use to calculate the rate of the succinate dehydrogenase reaction in the laboratory practice? Select one: a. the concentration of a reduced redox dye b. the concentration of an oxidized redox dye c. the used amount of succinate d. the produced amount of fumarate e. the produced amount of FAD

Answer 32

a. the concentration of a reduced redox dye

Question 33

Which one of the following components was not used in the laboratory practice in which succinate dehydrogenase activity was measured? Select one: a. phenolphtalein indicator b. malonate c. FTF (formate-Triton-formaldehyde solution) d. INT (iodonitrotetrazolium chloride) e. mitochondrial membrane

Answer 33

a. phenolphtalein indicator

Question 34

The inhibition of succinate dehydrogenase by malonate can be relieved by adding more of the following chemical to the enzyme system: Select one: a. FAD b. succinate c. fumarate d. malate e. ubiquinone

Answer 34

b. succinate

Question 35

Which one of the following statements is false regarding succinate dehydrogenase? Select one: a. the enzyme oxidizes succinate to fumarate b. the enzyme is bound to the inner mitochondrial membrane c. the enzyme contains Fe-S centers and an FAD prosthetic group d. the enzyme is part of the mitochondrial electron transport chain e. the enzyme pumps protons out of the matrix into the intermembrane space

Answer 35

e. the enzyme pumps protons out of the matrix into the intermembrane space

Question 36

Which one of the following statements is false? We can use the enzyme kinetic parameters (Km, vmax, kp) determined by Monte Carlo simulation... Select one: a. to identify the rate-limiting step of a metabolic pathway. b. to find the physiologically relevant substrate of a pathway. c. to decide which enzyme is saturated in vivo by its substrate (if in vivo [S] is known). d. to compare the turnover number of two enzymes. e. to calculate the standard Gibb’s free energy value of a reaction.

Answer 36

e. to calculate the standard Gibb’s free energy value of a reaction.

Question 37

Regarding the effect of pH and temperature on enzyme activity, which one of the following statements is true? Select one: a. Increasing the temperature will always lead to a decreased rate of the reaction as a result of protein denaturation. b. The changes of pH affect only the enzyme molecules, but not the substrates. c. The effect of temperature on the enzyme molecules is time-independent. d. The frequency of fruitful collisions of the reactant molecules is determined by their kinetic energy and thus by temperature. e. The plot v (reaction rate) versus T (temperature) is a linear ascending curve in the range of 0-90°C in the case of human enzymes.

Answer 37

d. The frequency of fruitful collisions of the reactant molecules is determined by their kinetic energy and thus by temperature.

Question 38

Which one of the following Michaelis-Menten assumptions is not correct? Select one: a. the [S] is much larger than the [E] b. the decrease in the [S] is more than 10% of the initial [S] c. the rate of the P → E+S reaction is negligible d. the [ES] is constant e. the increase of the [P] is linear

Answer 38

b. the decrease in the [S] is more than 10% of the initial [S]

Question 39

We identified the rate-limiting step of a metabolic pathway in the biochemistry class using computer simulation. How did we predict the flux-generating (rate-limiting) reaction of the S1 metabolic pathway? Select one: a. The in vivo Vmax of this reaction was high, and the in vivo substrate concentration was much greater than the Km. b. The in vivo Vmax of this reaction was low, and the in vivo substrate concentration was much greater than the Km. c. The in vivo Vmax of this reaction was high, and the in vivo substrate concentration was much less than the Km. d. The in vivo Vmax of this reaction was low, and the in vivo substrate concentration was much less than the Km.

Answer 39

b. The in vivo Vmax of this reaction was low, and the in vivo substrate concentration was much greater than the Km.

Question 40

Which statement is true regarding the regulation of pyruvate kinase L and M isoenzymes? Select one: a. cAMP dependent phosphorylation increases the affinity of PK-L for the activiting ligands b. Starvation increases the mRNA level of the PK-M isoenzyme. c. The PK-L isoenzyme is allosterically inhibited by ADP. d. Carbohydrate rich diet increases the mRNA level of the PK-M isoenzyme. e. The PK-M isoenzyme shows no allosteric behavior.

Answer 40

e. The PK-M isoenzyme shows no allosteric behavior.

Question 41

Which statement is false regarding the regulation of pyruvate kinase L and M isoenzymes? Select one: a. Carbohydrate rich diet increases the PK-L (liver) isoenzyme mRNA level. b. The PK-M (muscle) isoenzyme is allosterically inhibited by ATP or alanine. c. cAMP dependent phosphorylation decreases the affinity of PK-L for the activiting ligands. d. Starvation decreases the mRNA level of the PK-L isoenzyme. e. The PK-L isoenzyme is allosterically activated by fructose-1,6- bisphosphate.

Answer 41

b. The PK-M (muscle) isoenzyme is allosterically inhibited by ATP or alanine.

Question 42

Which parameter was measured in the laboratory practice in which we examined the pyruvate kinase (PK) catalyzed reaction? Select one: a. The absorbance changes of NADH, which was synthesized by pyruvate- dehydrogenase in a coupled enzyme reaction. b. The absorbance changes of NADPH, which was produced by hexokinase and glucose-6-phoshate dehydrogenase in a coupled enzyme reaction. c. The absorbance changes of phosphoenol-pyruvate, which was utilized by the PK catalyzed reaction. d. The absorbance changes of NADH, which was consumed by lactate- dehydrogenase in a coupled enzyme reaction. e. The absorbance changes of ATP, which was synthesized by the PK catalyzed reaction.

Answer 42

d. The absorbance changes of NADH, which was consumed by lactate- dehydrogenase in a coupled enzyme reaction.

Question 43

The rate of the reaction catalyzed by pyruvate kinase (PK) increases after.... Select one: a. pipetting alanine to the PK-L isoenzyme reaction mix. b. adding fructose-1,6-bisphosphate to the PK-M isoenzyme reaction mix. c. adding fructose-1,6-bisphosphate to the PK-L isoenzyme reaction mix. d. pipetting ATP to the PK-M isoenzyme reaction mix. e. adding alanine to the PK-M reaction mix.

Answer 43

c. adding fructose-1,6-bisphosphate to the PK-L isoenzyme reaction mix.

Question 44

The rate of the reaction catalyzed by pyruvate kinase (PK) decreases after... Select one: a. pipetting alanine to the PK-L isoenzyme reaction mix. b. adding fructose-1,6-bisphosphate to the PK-M isoenzyme reaction mix. c. adding fructose-1,6-bisphosphate to the PK-L isoenzyme reaction mix. d. pipetting ATP to the PK-M isoenzyme reaction mix. e. adding alanine to the PK-M isoenzyme reaction mix.

Answer 44

a. pipetting alanine to the PK-L isoenzyme reaction mix.

Question 45

Which statement is true regarding the measurement of pyruvate kinase activity in the laboratory practice? Select one: a. the mitochondrial fractions of liver and muscle were used for the experiments b. we demonstrated the activating effect of phosphoenolpyruvate on the PK- M isoenzyme c. the increase in lactate concentration was followed spectrophotometrically d. we demonstrated the activating effect of fructose-2,6-bisphosphate on the PK-L isoenzyme e. the reaction was initiated by the addition of ADP

Answer 45

e. the reaction was initiated by the addition of ADP

Question 46

Which statement is false regarding the measurement of pyruvate kinase activity in the laboratory practice? Select one: a. the reaction rate was measured using a coupled enzyme assay b. lactate was oxidized to pyruvate during the experiments c. the reaction mixture contained Mg2+ ions d. ATP was formed during the experiments e. NADH was oxidized during the experiments

Answer 46

b. lactate was oxidized to pyruvate during the experiments

Question 47

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

Answer 47

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

Question 48

How did we measure the enzyme activity of pancreatic lipase in the laboratory practice? Select one: a. free glycerol generation was measured by complexometry b. free fatty acid generation was followed by spectrophotometry c. free fatty acid generation was followed by titration with sodium hydroxide d. free fatty acid generation was followed by titration with HCl e. free glycerol generation was followed by spectrophotometry

Answer 48

c. free fatty acid generation was followed by titration with sodium hydroxide

Question 49

Which statement is true for the measurement of pancreatic lipase activity in the laboratory practice? Select one: a. we used olive oil as a substrate b. we used homogenized milk as substrate c. we excluded co-lipase from the reaction mixture d. we compared the activity of pancreatic lipase with that of lipoprotein lipase e. we added apoCII to the reaction mixture

Answer 49

b. we used homogenized milk as substrate

Question 50

Which statement is true for the measurement of pancreatic lipase activity in the laboratory practice? Select one: a. we compared pancreatic lipase activities in the absence and presence of milk b. we compared pancreatic lipase activities in the absence and presence of co-lipase c. we compared pancreatic lipase activities in the absence and presence of bile d. we studied the effect of NaOH on the pancreatic lipase activity e. we used formaldehyde in order to activate pancreatic lipase

Answer 50

c. we compared pancreatic lipase activities in the absence and presence of bile

Question 51

Which statement is true for the results of our laboratory experiments in which pancreatic lipase activity was measured? Select one: a. we proved that pancreatic lipase is regulated at the level of gene expression b. we found that pancreatic lipase was already active in the pancreas tissue c. we found a higher pancreatic lipase activity in the presence of bile d. our major conclusion was that formaldehyde stops the reaction e. the point of the experiments was to prove that phenolphthalein is pink at acidic pH

Answer 51

c. we found a higher pancreatic lipase activity in the presence of bile

Question 52

Which one of the following materials was not used for the laboratory experiment in which pancreatic lipase activity was measured? Select one: a. pancreatic extract b. NaOH c. phenol red indicator d. bile e. 10% formaldehyde solution

Answer 52

c. phenol red indicator

Question 53

Which statement is true regarding the laboratory experiment in which pancreatic lipase activity was measured? Select one: a.the triglycerides in the milk were already emulsified b. the bile used for the experiment contained co-lipase as well c. a weak base was used to titrate the liberated fatty acids d. the reaction was started by the addition of bile e. to evaluate the results we plotted the volume of the used bile versus the incubation time

Answer 53

a.the triglycerides in the milk were already emulsified

Question 54

Which effect of the bile acids was demonstrated in the laboratory experiment in which pancreatic lipase activity was measured? Select one: a. bile acids emulsify triglycerides in homogenized milk b. bile acids activate pro-co-lipase by proteolysis c. bile acids activate pancreatic lipase by inducing a conformational change d. bile acids activate co-lipase by inducing a conformational change e. bile acids activate pancreatic lipase by proteolysis

Answer 54

c. bile acids activate pancreatic lipase by inducing a conformational change

Question 55

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

Answer 55

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

Question 56

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

Answer 56

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

Question 57

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

Answer 57

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

Question 58

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

Answer 58

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 e. Acetyl CoA binds to a SH-group of the condensing enzyme

Question 59

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

Answer 59

All of them

Question 60

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

Answer 60

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

Question 61

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

Answer 61

All of them

Question 62

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

Answer 62

a. CoA c. FAD d. NAD

Question 63

Select the coenzyme needed for both b-oxidation and synthesis of fatty acids Select one: a. Biotin b. CoA c. FAD d. NAD e. NADP

Answer 63

b. CoA

Question 64

Select the coenzymes needed for the synthesis of fatty acids Select one or more: a. CoA b. NADP c. FAD d. NAD e. biotin

Answer 64

a. CoA b. NADP e. biotin

Question 65

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

Answer 65

a. Dihydroxyacetone d. a-hydroxybutyrate e. oxaloacetate

Question 66

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.

Answer 66

e. 1 FADH2 and 1 NADH.

Question 67

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

Answer 67

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

Question 68

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

Answer 68

a. insulin e. citrate

Question 69

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

Answer 69

e. Pancreatic lipase and bile acids

Question 70

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

Answer 70

a. a reaction requiring free CoA and ATP

Question 71

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

Answer 71

d. Creatine

Question 72

Which are the enzymes catalyzing the synthesis of fatty acids? Select one or more: a. Acetyl-CoA-carboxylase b. Ketoacyl-reductase c. Malonyl-transacylase d. Acetyl-(acyl) transacylase e. Ketoacyl-synthetase

Answer 72

All of them

Question 73

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

Answer 73

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

Question 74

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.

Answer 74

a. ATP, carnitine, and coenzyme A.

Question 75

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.

Answer 75

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

Question 76

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.

Answer 76

c. essential for intracellular transport of fatty acids.

Question 77

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.

Answer 77

d. malonyl-CoA

Question 78

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

Answer 78

c. 4

Question 79

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+.

Answer 79

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.

Question 80

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.

Answer 80

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.

Question 81

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

Answer 81

e. CH3--CO--CH2--CO--S—CoA

Question 82

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.

Answer 82

d. 8 mol of FADH2 are formed.

Question 83

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.

Answer 83

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

Question 84

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.

Answer 84

b. FADH2 serves as an electron carrier. d. Oxidation of an 18-carbon fatty acid produces six molecules of propionyl- CoA.

Question 85

The following fatty acid, in which the indicated carbon is labeled with 14C, is fed to an animal: 14CH3(CH2)9COOHAfter 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.

Answer 85

d. propionyl-CoA.

Question 86

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.

Answer 86

d. succinyl-CoA.

Question 87

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

Answer 87

c. CH3(CH2)11COOH

Question 88

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.

Answer 88

d. Liver.

Question 89

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

Answer 89

e. NADH

Question 90

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.

Answer 90

d. All of the above are true.

Question 91

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.

Answer 91

b. It requires acyl carrier protein (ACP).

Question 92

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.

Answer 92

d. No part of the molecule.

Question 93

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.

Answer 93

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

Question 94

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.

Answer 94

d. The processes occur in the mitochondrial matrix.

Question 95

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.

Answer 95

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

Question 96

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.

Answer 96

d. the reaction catalyzed by acetyl-CoA carboxylase.

Question 97

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.

Answer 97

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

Question 98

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.

Answer 98

b. ATP.