Mistakes

Question 1

Answer 1

Up -> serine

Down -> Threonine

Question 2

Which of the following amino acids have a negatively charged side chain at neutral pH?
Select one or more:

a. Arginine
b. Alanine
c. Asparagine
d. Aspartate
e. Glutamate

Answer 2

d. Aspartate

e. Glutamate

Question 3

Which of the following amino acids have sulfur-containing side chains?
Select one or more:

a. Histidine
b. Cysteine
c. Methionine
d. Proline
e. Valine

Answer 3

b. Cysteine

c. Methionine

Question 4

Which amino acid has a guanidine group in its side chain?

Select one:

a. Histidine
b. Lysine
c. Tyrosine
d. Arginine
e. Tryptophan

Answer 4

d. Arginine

Question 5

Which of the following amino acids have four carbon atoms?
Select one or more:

a. Aspartate
b. Threonine
c. Asparagine
d. Proline

Answer 5

a. Aspartate
b. Threonine
c. Asparagine

Question 6

Which of the following amino acids have five carbon atoms?

Select one or more:

a. Glutamate
b. Glutamine
c. Histidine
d. Proline
e. Glycine

Answer 6

a. Glutamate
b. Glutamine
d. Proline

Question 7

Which of the following amino acids have six carbon atoms?

Select one or more:

a. Leucine
b. Isoleucine
c. Histidine
d. Proline
e. Glycine

Answer 7

a. Leucine
b. Isoleucine
c. Histidine

Question 8

Pair the amino acids with their character! 1. Proline 2. Arginine 3. Glutamate
a. neutral b. acidic c. basic

Select one:

a. 1-a, 2-c, 3-b
b. 1-a, 2-b, 3-c
c. 1-b, 2-c, 3-a
d. 1-b, 2-a, 3-c
e. 1-c, 2-a, 3-b

Answer 8

a. 1-a, 2-c, 3-b

Question 9

Select the correct statements! I

Select one or more:

a. Acidic amino acids have a net negative charge at neutral pH.
b. The isoelectric point of acidic amino acids is at acidic pH.
c. The isoelectric point of the acidic amino acids can be calculated as the average of their three pKa values.
d. Asparagine is an acidic amino acid.

Answer 9

a. Acidic amino acids have a net negative charge at neutral pH.
b. The isoelectric point of acidic amino acids is at acidic pH.

Question 10

What is the dominant form of Arginine at pH 6.0? (pKa values of Arginine are 2.2, 9.0 and 12.5).
Select one:

a. Two positive and one negative charges
b. One positive and two negative charges
c. One negative and one positive charges
d. One negative charge e. One positive charge

Answer 10

a. Two positive and one negative charges

(Why?
1st deprotonation of alpha carboxyl group.
=> Arginine is a basic amino acid
=> (-) deprotonated alpha-carboxyl group; (+) R chain; (+) alpha-amino group
=> 2 (+) & 1 (-)

Question 11

What is the dominant form of Glutamate at pH 7.0?
(pKa values of Glutamate are 2.2, 5.6 and 9.2).

Select one:

a. One negative charge
b. One negative and one positive charges
c. One positive and two negative charges
d. One positive charge

Answer 11

c. One positive and two negative charges

Question 12

What is the dominant form of Histidine at pH 8.0? (pKa values of Histidine are 1.8, 6.0 and 9.2).

Select one:

a. One positive and one negative charges
b. Two negative and one positive charges
c. One negative charge
d. One positive charge

Answer 12

a. One positive and one negative charges

Question 13

Select the correct statements!

Select one or more:

a. Glutamate has a negative charge on its side chain at the isoelectric pH.
b. Glutamate has a negative charge on its side chain at neutral pH.
c. Arginine has a positive charge on its side chain at the isoelectric pH.
d. Arginine has a positive charge on its side chain at neutral pH.

Answer 13

b. Glutamate has a negative charge on its side chain at neutral pH.
c. Arginine has a positive charge on its side chain at the isoelectric pH.
d. Arginine has a positive charge on its side chain at neutral pH.

( A is incorrect -> at isoelectric point, the deprotonation of side chain does not occur before the next pKa value)

Question 14

Which of the following statements are true for the isoelectric form of amino acids?

Select one or more:

a. All the naturally occurring amino acids have one positive and one negative charges.
b. The a-amino group of all the naturally occurring amino acids has a positive charge.
c. The a-carboxyl group of all the naturally occurring amino acids has a negative charge.

Answer 14

All are correct

(at isoelectric point, the a-amino group is not deprotonated and have (+), whereas deprotonated carboxyl group ihas (-)
=> net charge = 0 (aka isoelectric point)

Question 15

At neutral pH a tetrapeptide of glycylalanylarginylglutamate has…

Select one:

a. two positive and three negative charges
b. two positive and one negative charges
c. one positive and one negative charges
d. one positive and two negative charges
e. two positive and two negative charges

Answer 15

e. two positive and two negative charges

(glycine has a free amino group => (+)
Glutamate has a free carboxyl group = 1 (-)
Glutamate is acidic => 1 (-)
Arginine is basic => 1 (+)
The bonds between amino acids => 0 charge
=> Total = 2 (+) & 2 (-) )

Question 16

The arginyllysylaspartate tripeptide has
Select one or more:

a. its isoelectric point at basic pH.
b. three positive and two negative charges at neutral pH.
c. two positive and two negative charges at its isoelectric point

Answer 16

All are correct

this tripeptide has 2 basic aa => pKI is basic

Question 17

The chirality of an amino acid results from the fact that its a—carbon…

Select one:

a. is bonded to four different chemical groups.
b. is a carboxylic acid.
c. is symmetric.
d. is in the L absolute configuration in naturally occurring proteins.
e. has no net charge.

Answer 17

a. is bonded to four different chemical groups.

Question 18

For amino acids with neutral side chain, at any pH below the pI of the amino acid, the population of amino acids in solution will:
Select one:

a. have a net positive charge.
b. have no charged groups.
c. have no net charge.
d. have positive and negative charges in equal concentration.
e. have a net negative charge.

Answer 18

a. have a net positive charge.

because of protonated alpha amino group

Question 19

An octapeptide composed of four repeating glycylalanyl units has:

Select one:

a. a single free amino group on an alanyl residue.
b. two free amino and two free carboxyl groups.
c. a single free amino group on a glycyl residue and a single free carboxyl group on an alanyl residue
d. two free carboxyl groups, both on glycyl residues.
e. a single free amino group on an alanyl residue and a single free carboxyl group on a glycyl residue.

Answer 19

c. a single free amino group on a glycyl residue and a single free carboxyl group on an alanyl residue

Question 20

The backbone of two amino acid residues in a protein can be described as (where Ca is C-alpha):

Select one:

a. Ca–C–N–Ca–C–N
b. Ca–N–Ca–C–Ca–N–Ca–C
c. Ca–N–C–C–N–Ca–
d. C–N–Ca–Ca–C–N
e. Ca–Ca–C–N–Ca–Ca–C

Answer 20

a. Ca–C–N–Ca–C–N

Question 21

By adding SDS (sodium dodecyl sulfate) during the electrophoresis of proteins, it is possible to:

Select one:

a. preserve a protein’s native structure and biological activity
b. separate proteins exclusively on the basis of molecular weight.
c. determine a protein’s isoelectric point.
d. determine the amino acid composition of the protein.
e. determine an enzyme’s specific activity.

Answer 21

b. separate proteins exclusively on the basis of molecular weight.

Question 22

Specific enzyme activity:
Select one:

a. is the enzyme activity (expressed as units'') of a specific protein. b. is the enzyme activity (enzyme asunits’’) in a milligram of protein.
c. is the enzyme activity (expressed as ``units’’) in a mol of protein.
d. refers to proteins other than enzymes.
e. refers only to purified proteins.

Answer 22

b. is the enzyme activity (enzyme as ``units’’) in a milligram of protein.

Question 23

In the a helix the hydrogen bonds:
Select one:

a. occur only between some of the amino acids of the helix.
b. occur mainly between electronegative atoms of the R groups.
c. are perpendicular to the axis of the helix.
d. occur mainly between electronegative atoms of the backbone.
e. occur only near the amino and carboxyl termini of the helix.

Answer 23

d. occur mainly between electronegative atoms of the backbone.

Question 24

Thr and/or Leu residues tend to disrupt an a-helix when they occur next to each other in a protein because:

Select one:
a. of the possible covalent interactions between the Thr and/or Leu side chains.

b. both amino acids are highly hydrophobic.
c. the R group of neither amino acid can form a hydrogen bond.
d. of electrostatic repulsion between the Thr and/or Leu side chains.
e. of steric hindrance between the bulky Thr and/or Leu side chains

Answer 24

e. of steric hindrance between the bulky Thr and/or Leu side chains

( This is when a large group in a molecule makes reactions not work)

Question 25

Amino acid residues commonly found at the end of b turn are: Select one: a. Pro and Gly. b. Ala and Gly. c. two Cys. d. hydrophobic. e. those with ionized R groups.

Answer 25

a. Pro and Gly. (Proline alpha-imino group cannot form H-bond => cause a break/kink Glycine does not have beta carbon)

Question 26

A sequence of amino acids in a certain protein is found to be -Ser-Gly-Pro- Gly-. The sequence is most probably part of: Select one: a. b turn. b. parallel b sheet. c. a helix. d. a--sheet.

Answer 26

a. b turn.

Question 27

The three-dimensional conformation of a protein may be strongly influenced by amino acid residues that are very far apart in sequence. This relationship is in contrast to secondary structure, where the amino acid residues are: Select one: a. restricted to only about seven of the twenty standard amino acids found in proteins b. always side by side. c. generally on different polypeptide strands. d. generally near the polypeptide chain's amino terminus or carboxyl terminus. e. generally near each other in sequence.

Answer 27

e. generally near each other in sequence.

Question 28

Which of the following statements is false? Select one: a. a-keratin is a protein in which the polypeptides are mainly in the a-helix conformation b. Silk fibroin is a protein in which the polypeptide is almost entirely in the b conformation. c. Collagen is a protein in which the polypeptides are mainly in the a-helix conformation d. Gly residues are particularly abundant in collagen. e. Mutations in collagen have been shown to be responsible for some human diseases

Answer 28

c. Collagen is a protein in which the polypeptides are mainly in the a-helix conformation (single collagen polypeptides -> left handed helices 3 collagen polypeptide bundles -> right-handed helix)

Question 29

To alter the shape of the a-keratin chains--as in hair waving-- the a-keratin chains have undergone one chemical step resulting the conversion of disulfide bridges to Cysteine. What subsequent steps are required? Select one: a. chemical reduction and then chemical oxidation b. chemical oxidation and then shape remodeling c. shape remodeling and then chemical reduction d. shape remodeling and then chemical oxidation e. chemical reduction and then shape remodeling

Answer 29

d. shape remodeling and then chemical oxidation

Question 30

When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe2+ are occupied by: Select one: a. two O2 molecules. b. two O atoms. c. one O2 molecule and one heme atom. d. one O2 molecule and one amino acid atom. e. one O atom and one amino acid atom.

Answer 30

d. one O2 molecule and one amino acid atom.

Question 31

In haemoglobin, the transition from T state to R state (low to high affinity) is triggered by: Select one: a. subunit dissociation. b. oxygen binding. c. Fe2+ binding. d. heme binding. e. subunit association.

Answer 31

b. oxygen binding.

Question 32

Which of the following is not correct concerning 2,3-bisphosphoglycerate (BPG)? Select one: a. It is normally found associated with the haemoglobin molecules that are extracted from red blood cells. b. It decreases the affinity of haemoglobin for oxygen. c. It binds to the heme groups of haemoglobin. d. It is an allosteric modulator. e. It binds with lower affinity to foetal haemoglobin than to adult haemoglobin.

Answer 32

c. It binds to the heme groups of haemoglobin. | binds to the central compartment of the hemoglobin tetrame

Question 33

To calculate the turnover number of an enzyme you need to know the: Select one or more: a. initial velocity of the catalyzed reaction at low [S]. b. initial velocity of the catalyzed reaction at [S] >> KM. c. KM for the substrate. d. enzyme concentration.

Answer 33

b. initial velocity of the catalyzed reaction at [S] >> KM. | d. enzyme concentration.

Question 34

Enzyme X exhibits maximum activity at pH = 6.9. X shows a fairly sharp decrease in its activity when the pH goes much lower than 6.4. One likely interpretation of this pH activity is that: Select one: a. the enzyme is found in gastric secretions b. a Lysine residue on the enzyme is involved in the reaction. c. a Glutamate residue on the enzyme is involved in the reaction. d. a Histidine residue on the enzyme is involved in the reaction. e. the enzyme has a metallic cofactor.

Answer 34

d. a Histidine residue on the enzyme is involved in the reaction.

Question 35

A good transition-state analog: Select one: a. binds to the enzyme more tightly than the substrate. b. binds covalently to the enzyme. c. is too unstable to isolate. d. binds very weakly to the enzyme. e. does not react with the native enzyme

Answer 35

a. binds to the enzyme more tightly than the substrate.

Question 36

A transition-state analog: Select one: a. resembles the active site of general acid-base enzymes. b. typically reacts more rapidly with an enzyme than the normal substrate. c. is less stable when binding to an enzyme than the normal substrate. d. stabilizes the transition state for the normal enzyme-substrate complex. e. resembles the transition-state structure of the normal enzyme-substrate complex

Answer 36

e. resembles the transition-state structure of the normal enzyme-substrate complex

Question 37

Both water and glucose share an --OH that can serve as a substrate for a reaction with the terminal phosphate of ATP catalyzed by hexokinase. Glucose, however, is about a million times more reactive as a substrate than water. The best explanation is that: Select one: a. the larger glucose binds better to the enzyme; it induces a conformational change in hexokinase that brings active-site amino acids into position for catalysis. b. glucose has more --OH groups per molecule than does water. c. water normally will not reach the active site because it is hydrophobic. y d. water and ATP compete for the active site resulting in a competitive inhibition of the enzyme. e. the --OH group of water is attached to an inhibitory H atom while the glucose --OH group is attached to C.

Answer 37

a. the larger glucose binds better to the enzyme; it induces a conformational change in hexokinase that brings active-site amino acids into position for catalysis

Question 38

Which of the following statements about allosteric control of enzymatic activity is false? Select one: Ia. Allosteric proteins are generally composed of several subunits. b. Heterotropic allosteric effectors compete with substrate for binding sites. c. Binding of the effector changes the conformation of the enzyme molecule. d. An effector may either inhibit or activate an enzyme. e. Homotropic allosteric effectors do not have a separate binding site.

Answer 38

e. Homotropic allosteric effectors do not have a separate binding site.

Question 39

Which of the following statements are true for the enzyme at the rate-limiting step of a metabolic pathway? a. Concentration of its substrate is higher than its Km value b. The measured reaction rate is close to its Vmax c. Its Vmax is higher than that of other enzymes in the pathway d. Its Km value is higher than that of other enzymes in the pathway e. Its Km value is lower than that of other enzymes in the pathway

Answer 39

a. Concentration of its substrate is higher than its Km value b. The measured reaction rate is close to its Vmax

Question 40

Which of the following statements is true for a reaction pathway under conditions of steady-state? a. Concentrations of intermediers are unaltered b. Vmax values of enzymes involved are equal c. Reaction rate at the rate-limiting step is the lowest d. Concentrations of intermediers are equal e. The system is in thermodynamic equilibrium

Answer 40

a. Concentrations of intermediers are unaltered

Question 41

Which conditions are necessary for two reactions to be enzymatically coupled? (Eact: activation energy) a. Both reactions include phosphoryl transfer. b. Eact of both reactions is high. c. At least one of the reactions is oxidoreduction. d. ΔG of the two reactions has different signs (one negative and one positive). e. Eact of both reactions is low.

Answer 41

d. ΔG of the two reactions has different signs (one negative and one positive).

Question 42

Which conditions rule out the enzymatic coupling of two reactions? (Eact: activation energy) a. One of the reactions has low Eact. b. Eact of both reactions is high. c. ΔG of both reactions is negative. d. ΔG of the two reactions has different signs (one negative and one positive). e. One of the reactions is oxidoreduction.

Answer 42

a. One of the reactions has low Eact. | c. ΔG of both reactions is negative.

Question 43

Which statement is true regarding the group transfer potential (gtp)? Select one or more: a. Gtp is the absolute value of the ΔG of hydrolysis (when the group is released). b. Functional groups have a natural tendency to move from the lower toward the higher gtp. c. Functional groups have a natural tendency to move from the higher toward the lower gtp. d. ΔG of a group transfer equals the gtp of the group acceptor plus the gtp of the group donor. e. ΔG of a group transfer equals the gtp of the group acceptor minus the gtp of the group donor.

Answer 43

a. Gtp is the absolute value of the ΔG of hydrolysis (when the group is released). c. Functional groups have a natural tendency to move from the higher toward the lower gtp. e. ΔG of a group transfer equals the gtp of the group acceptor minus the gtp of the group donor.

Question 44

Which statement is false regarding the group transfer potential (gtp)? Select one or more: a. The molecule of the lowest gtp is suitable as a group carrier. b. Functional groups have a natural tendency to move from the lower toward the higher gtp. c. ΔG of a group transfer equals the gtp of the group donor minus the gtp of the group acceptor. d. Low gtp means that the group is attached to the molecule with a weak bond. e. High gtp indicates a great tendency of the molecule to accept the group.

Answer 44

All are correct

Question 45

Which statement is false regarding oxidative decarboxylation of pyruvate in human cells? Select one or more: a. It is an irreversible reaction but it can be undone (i.e. pyruvate can be regenerated from the products) by other enzymes. b. It is catalyzed by a large enzyme complex (E1, E2 and E3) in the cytosol. c. The process can occur in anaerobic conditions because the complex does not use O2. d. It belongs to substrate level phosphorylation because an ATP is produced. e. The prosthetic group of E1 is biotin, which is reoxidized by E3 in each catalytic cycle.

Answer 45

All correct | for b, the enzyme complex is in mitochondria

Question 46

Which statement is false regarding oxidative decarboxylation of pyruvate in human cells? Select one or more: a. It is catalyzed by homodimers of pyruvate decarboxylase in the mitochondrial matrix. b. The acetaldehyde intermediate is covalently bound to the enzyme as a hydroxyethyl group. c. The product, acetate is bound to CoA in a macroergic thioester bond. d. It is coupled to the mitochondrial electron transfer chain by NAD+ and NADH. e. It is the last step of anaerobic glycolysis and it produces lactate

Answer 46

a. It is catalyzed by homodimers of pyruvate decarboxylase in the mitochondrial matrix. (=> catalyzed by pyruvate dehydrogenase to covert into acetyl-coA) e. It is the last step of anaerobic glycolysis and it produces lactate

Question 47

Which statement is true? Select one or more: a. Oxidative phosphorylation is activated by ATP in starvation. b. Oxidative catabolic processes in the mitochondrial matrix are coupled to respiration. c. Citrate cycle is inhibited by high NADH/NAD+ ratio. d. Pyruvate dehydrogenase is activated by low ATP/ADP ratio. e. Malate/aspartate shuttle transports electrons from fatty acid oxidation to respiration.

Answer 47

b. Oxidative catabolic processes in the mitochondrial matrix are coupled to respiration. c. Citrate cycle is inhibited by high NADH/NAD+ ratio. d. Pyruvate dehydrogenase is activated by low ATP/ADP ratio.

Question 48

Which statement is false? Select one or more: a. Substrate level phosphorylation occurs both in glycolysis and in citrate cycle. b. Uncouplers of oxidative phosphorylation cause inhibition of oxidative catabolism. c. Pyruvate dehydrogenase and citrate cycle cannot function in anaerobic conditions. d. ADP activates oxidative phosphorylation as a substrate of FoF1 ATPase. e. FoF1 ATPase is an active transporter, which can pump protons into the matrix.

Answer 48

b. Uncouplers of oxidative phosphorylation cause inhibition of oxidative catabolism. e. FoF1 ATPase is an active transporter, which can pump protons into the matrix.

Question 49

Which statement is false? Select one or more: a. Citrate cycle does not use O2, therefore it can function in anaerobic conditions. b. Uncouplers of oxidative phosphorylation cause activation of oxidative catabolism. c. Oxidative phosphorylation is uncoupled when the inner mitochondrial membrane is permeable for ions. d. Respiration can be inhibited by KCN when oxidative phosphorylation is uncoupled. e. Respiration can be inhibited by oligomycin when oxidative phosphorylation is uncoupled

Answer 49

a. Citrate cycle does not use O2, therefore it can function in anaerobic conditions. e. Respiration can be inhibited by oligomycin when oxidative phosphorylation is uncoupled (Oligomycin A is an inhibitor of ATP synthase)

Question 50

Which is prosthetic group in pyruvate-dehydrogenase complex? Select one or more: a. flavine mononucleotide (FMN), b. CoA, c. thiamine pyrophosphate (TPP), d. heme, e. flavine adenine dinucleotide (FAD).

Answer 50

c. thiamine pyrophosphate (TPP), | e. flavine adenine dinucleotide (FAD).

Question 51

Which cofactor is involved in the oxidative decarboxylation of pyruvate? Select one or more: a. CoA, b. flavine mononucleotide (FMN), c. CoQ, d. NAD+, e. biotine.

Answer 51

a. CoA, | d. NAD+,

Question 52

Which enzyme contains FAD prosthetic group? Select one or more: a. α-ketoglutarate dehydrogenase complex, b. E3 of PDH complex, c. mitochondrial glycerol 3-phosphate dehydrogenase, d. succinate dehydrogenase, e. malate dehydrogenase.

Answer 52

a. α-ketoglutarate dehydrogenase complex, c. mitochondrial glycerol 3-phosphate dehydrogenase, b. E3 of PDH complex, d. succinate dehydrogenase,

Question 53

Which enzyme contains FAD prosthetic group? Select one or more: a. Complex I of the respiratory chain, b. α -ketoglutarate dehydrogenase, c. malate dehydrogenase, d. pyruvate dehydrogenase complex, e. isocitrate dehydrogenase.

Answer 53

b. α -ketoglutarate dehydrogenase, | d. pyruvate dehydrogenase complex,

Question 54

Which enzyme uses NAD+/NADH? Select one or more: a. Complex I of the respiratory chain, b. succinate dehydrogenase, c. malate dehydrogenase, d. acyl-CoA dehydrogenase, e. glyceraldehyde 3-phosphate dehydrogenase.

Answer 54

a. Complex I of the respiratory chain, c. malate dehydrogenase, e. glyceraldehyde 3-phosphate dehydrogenase.

Question 55

Which enzyme consumes ATP in glycolysis? Select one or more: a. 3-Phosphoglycerate kinase, b. phosphofructokinase, c. hexokinase, d. pyruvate kinase, e. pyruvate dehydrogenase kinase.

Answer 55

b. phosphofructokinase, | c. hexokinase,

Question 56

Which compound is allosteric activator for phosphofructokinase 1 (PFK1)? Select one or more: a. AMP, b. citrate, c. fructose 2,6-bisphosphate, d. glucagon, e. acyl-CoA.

Answer 56

c. fructose 2,6-bisphosphate, (Fructose 2,6-bisphosphate is synthesized from fruc- tose 6-phosphate and ATP by an enzyme called PFK 2 and it is hydrolyzed into fruc- tose 6-phosphate and P. by a specific fruc- tose 2,6-bisphosphatase also called FBPase 2.)

Question 57

Which compound is allosteric inhibitor for phosphofructokinase 1 (PFK1)? Select one or more: a. AMP, b. citrate, c. fructose 2,6-bisphosphate, d. glucagon, e. acyl-CoA.

Answer 57

b. citrate, | e. acyl-CoA.

Question 58

Which is the major role of lactate dehydrogenase (LDH) reaction in anaerobic glycolysis? Select one: a. production of ATP, b. elimination of hydrogen, c. elimination of lactate, d. regeneration of NAD+, e. regeneration of pyruvate.

Answer 58

d. regeneration of NAD+,

Question 59

Which is not involved in oxidative decarboxylation of pyruvate by PDH complex? Select one: a. lipoamide, b. biotin, c. FAD, d. CoA, e. NAD+

Answer 59

b. biotin,

Question 60

Which is not involved in oxidative decarboxylation of pyruvate by PDH complex? Select one: a. thiamine pyrophosphate, b. FAD, c. NAD+, d. ubiquinone, e. CoA.

Answer 60

ubiquinone

Question 61

Chose the correct/right sentence regarding hepatic phosphofructokinase1 (PFK1). Select one: a. Insulin increases fructose 2,6-bisphosphate level and hence activates PFK1. b. Insulin decreases fructose 2,6-bisphosphate level and hence activates PFK1. c. Insulin causes phosphorylation and activation of PFK1. d. Glucagon causes phosphorylation and activation of PFK1. e. Glucagon decreases fructose 2,6-bisphosphate level and hence activates PFK1.

Answer 61

a. Insulin increases fructose 2,6-bisphosphate level and hence activates PFK1.

Question 62

Chose the wrong/false sentence regarding hepatic phosphofructokinase (PFK) enzymes. Select one: a. Insulin causes dephosphorylation of PFK2 and activation of PFK1. b. PFK2 uses ATP for irreversible phosphorylation of fructose 6-phosphate. c. PFK1 is allosterically activated by AMP. d. PFK1 is allosterically inhibited by citrate. e. PFK1 is allosterically inhibited by fructose 2,6-bisphosphate.

Answer 62

e. PFK1 is allosterically inhibited by fructose 2,6-bisphosphate. (PFK2 produce F 2.6 BP, which in turn activates PFK1)

Question 63

Chose the correct/right sentence regarding hepatic glycolysis. Select one: a. Hepatic glycolysis is activated in starvation for ATP production. b. Hepatic glycolysis is inhibited by glucagon at two irreversible steps. c. Hepatic glycolysis results in lactate production. d. Hepatic glycolysis is activated when fructose 2,6-bisphosphate level decreases. e. Hepatic glycolysis is inhibited when AMP level increases.

Answer 63

b. Hepatic glycolysis is inhibited by glucagon at two irreversible steps. (In addition to increasing gluconeogenesis, glucagon inhibits glycolysis. Phosphofructokinase-1 (PFK-1) phosphorylates the C-1 position of F-6-P, converting F-6-P into F(1,6)P2, an early and rate-limiting step in glycolysis.)

Question 64

Chose the wrong/false sentence regarding hepatic phosphofructokinase (PFK) enzymes. Select one: a. Hepatic glycolysis is aerobic and it is followed by conversion of pyruvate to acetyl-CoA. b. PFK-1 becomes activated if PFK-2 is dephosphorylated. c. Hepatic glycolysis is inhibited when citrate level increases. d. Hepatic glycolysis is activated in starvation by fructose 2,6-bisphosphate. e. Hepatic glycolysis is activated when AMP level increases.

Answer 64

d. Hepatic glycolysis is activated in starvation by fructose 2,6-bisphosphate.

Question 65

Chose the correct/right sentence (PDH: pyruvate dehydrogenase complex). Select one: a. Pyruvate activates PDH kinase and hence inhibits PDH. b. Insulin activates PDH kinase and hence activates PDH. c. ADP inhibits PDH kinase and hence activates PDH. d. Ca2+ activates PDH phosphatase and hence inhibits PDH. e. NADH activates PDH phosphatase and hence activates PDH.

Answer 65

c. ADP inhibits PDH kinase and hence activates PDH.

Question 66

Which compound can deliver electrons to the respiratory chain directly? Select one: a. Fatty acyl-CoA b. Fumarate c. Succinyl-CoA d. Pyruvate e. Oxaloacetate

Answer 66

a. Fatty acyl-CoA | carnitine carrier system

Question 67

``` Which compound cannot deliver electrons to the respiratory chain directly? Select one: a. Glycerol 3-phosphate b. NADH c. Acetyl-CoA d. Fatty acyl-CoA e. Succinate ```

Answer 67

c. Acetyl-CoA

Question 68

Which component of the oxidative phosphorylation is localized in the inter-membrane space? Select one: a. Cytochrome a3 b. Ubiquinone (CoQ) c. Fo subunit of ATP synthase d. Cytochrome c e. F1 subunit of ATP synthase

Answer 68

d. Cytochrome c

Question 69

The branches in glycogen consist of glucose molecules linked by Select one: a. alpha-1,5 linkages b. alpha-1,4 linkages c. alpha-1,6 linkages d. alpha-1,2 linkages

Answer 69

c. alpha-1,6 linkages

Question 70

The straight glucose chains of glycogen molecules are broken down initially to Select one: a. glucose b. glucose- 6- phosphate c. glucose-1- phosphate d. fructose diphosphate e. UDP-glucose

Answer 70

c. glucose-1- phosphate

Question 71

The branch points of glycogen are broken down to Select one: a. fructose diphosphate b. glucose c. glucose- 1- phosphate d. glucose -6- phosphate e. UDP-glucose

Answer 71

b. glucose

Question 72

The straight chains of glycogen molecules are broken down by Select one: a. adenylate cyclase b. glycogen glicosidase c. glycogen phosphorylase d. glycogen-glycosidase e. protein kinase

Answer 72

c. glycogen phosphorylase

Question 73

The binding of epinephrine to a receptor Select one: a. deactivates protein kinase A b. deactivates adenylate cyclase c. causes the breakdown of cyclic AMP to ATP d. activates phosphodiesterase e. activates adenylate cyclase

Answer 73

e. activates adenylate cyclase

Question 74

The binding of glucagon to its receptor Select one: a. deactivates protein kinase b. deactivates adenylate cyclase c. causes the breakdown of cyclic AMP to ATP d. activates adenylate cyclase e. activates phosphodiesterase

Answer 74

d. activates adenylate cyclase

Question 75

Which of the following statements are true? Select one: a. Fructose-1-phosphate activates glucokinase b. Fructose-6-phosphate activates glucokinase c. Glucokinase is inhibited by glucose-6-phosphate d. Glucokinase is inhibited by high glucose level e. Glucokinase is sequestered in the nucleus when glucose level is high.

Answer 75

a. Fructose-1-phosphate activates glucokinase

Question 76

``` Protein kinase A directly Select one: a. deactivates glucokinase b. deactivates glycogen phosphorylase c. activates glycogen phosphorylase d. deactivates phosphorylase kinase e. activates phosphorylase kinase ```

Answer 76

e. activates phosphorylase kinase

Question 77

In glycogenesis, the enzyme (i)________ uses a molecule of (ii)_________ to lengthen the glycogen chain Select one: a. (i) glycogen synthase (ii) glucose b. (i)glycogen phosphorylase (ii) glucose c. (i) glycogen phosphorylase (ii) UDP-glucose d. (i) glycogen synthase (ii) UDP-glucose e. (i) glycogenin (ii) glucose-1-phosphate

Answer 77

c. (i) glycogen phosphorylase (ii) UDP-glucose

Question 78

Patients suffering from Von Gierke's disease Select one: a. cannot convert glucose-6-phosphate to glucose b. have enlarged livers c. cannot convert glycogen to glucose d. have high plasma levels of lactate e. all of them are correct

Answer 78

e. all of them are correct

Question 79

A person is suffering from a disease which is caused by a defective glucose-6-phosphatase. Such a person Select one: a. cannot breakdown glycogen completely to glucose b. can convert pyruvate to glucose c. can dephosphorylate glucose-6-phosphate d. can convert glycogen to pyruvate e. can convert acetyl-CoA to glucose

Answer 79

a. cannot breakdown glycogen completely to glucose

Question 80

In glycogenolysis, the enzyme (i)________ breaks an (ii) _______ bond to release a molecule of (iii)_________. Select one: a. (i) glycogen synthase (ii) alpha 1-4 (iii) glucose b. (i) glycogen synthase (ii) alpha 1-4 (iii) UDP-glucose c. (i) glycogen phosphorylase (ii) alpha 1-4 (iii) glucose-1-phosphate d. (i) glycogen phosphorylase (ii) alpha 1-6 (iii) glucose-6-phosphate e. (i) debranching enzyme (ii) alpha 1-6 (iii) glucose-1-phosphate

Answer 80

(i) glycogen phosphorylase (ii) alpha 1-4 (iii) glucose-1-phosphate

Question 81

In glycogenolysis, the enzyme (i)________ breaks an (ii) _______ bond to release a molecule of (iii)_________. Select one: a. (i) glycogen synthase (ii) alpha 1-4 (iii) glucose b. (i) glycogen synthase (ii) alpha 1-4 (iii) UDP-glucose c. (i) glycogen phosphorylase (ii) alpha 1-4 (iii) glucose-1-phosphate d. (i) glycogen phosphorylase (ii) alpha 1-6 (iii) glucose-6-phosphate e. (i) debranching enzyme (ii) alpha 1-6 (iii) glucose-1-phosphate

Answer 81

(i) glycogen phosphorylase (ii) alpha 1-4 (iii) glucose-1-phosphate

Question 82

What is true concerning glucose-6-phosphatase enzyme system? Select one or more: a. responsible for dephosphorylation of glucose-6-phosphate b. expressed in the endoplasmic reticulum of hepatocytes c. an enzyme system in gluconeogenic pathway d. is involved in pentose-phosphate pathway

Answer 82

a. responsible for dephosphorylation of glucose-6-phosphate b. expressed in the endoplasmic reticulum of hepatocytes c. an enzyme system in gluconeogenic pathway

Question 83

Activity of phosphofructokinase1 is inhibited by Select one or more: a. ATP b. citrate c. fructose 2,6 bisphosphate d. AMP

Answer 83

a. ATP | b. citrate

Question 84

Which are the ATP producing steps of glycolysis? Select one or more: a. phosphofructokinase 1 b. lactate-dehydrogenase c. pyruvate kinase d. glyceraldehyde 3-phosphate dehydrogenase e. phosphoglycerate kinase

Answer 84

pyruvate kinase, phosphoglycerate kinase

Question 85

``` Which are the ATP consuming steps of glycolysis? Select one or more: a. phosphofructokinase 1 b. lactate dehydrogenase c. pyruvate kinase d. hexokinase e. phosphoglycerate kinase ```

Answer 85

phosphofructokinase 1, hexokinase

Question 86

Upon phosphorylation of phosphofructokinase 2 by protein kinase A in liver: Select one: a. it becomes active. b. it becomes inactive. c. phosphatase function is activated, kinase function is inactivated. d. kinase function is activated, phosphatase function is inactivated. e. phosphofructokinase 2 is not covalently regulated.

Answer 86

c. phosphatase function is activated, kinase function is inactivated.

Question 87

Which enzyme deficiency may result in lactic acidosis? Select one or more: a. Pyruvate kinase b. Pyruvate dehydrogenase c. Pyruvate carboxylase d. Lactate dehydrogenase

Answer 87

b. Pyruvate dehydrogenase c. Pyruvate carboxylase (=> accumulation of pyruvate)

Question 88

Which condition is not found in pyrvate carboxylase deficiency? Select one: a. Demyelination b. Hyperammonemia c. Hyperglycemia d. Hypoglycemia e. Lactic acidosis

Answer 88

c. Hyperglycemia | high. blood sugar