Carbohydrates Metabolism Biochemistry 2023

Question 1 of 69

Which of the following statements regarding the enzyme phosphoenolpyruvate carboxykinase (PEPCK) is NOT true?

It undergoes regulation at the gene level.
It requires a triphosphate in the reaction it catalyzes.
It has one four-carbon substrate.
It is made in the heart.
It produces a glycolysis intermediate.

Question 2 of 69

Which of the following regarding glycolysis is true?

All the energy needed to perform all cell functions are produced.
It produces 2 ATP, 2 pyruvates, and 2 NADH.
Glucose is converted to one molecule of pyruvate.
ADP is required to start the process.
All the reactions take place in the mitochodria.

Question 3 of 69

Which of the following statements about pyruvate kinase is NOT true?

It is both the last enzyme of glycolysis and a regulated enzyme of glycolysis.
The reaction it catalyzes is readily reversible.
The reaction it catalyzes releases a large amount of energy.
It catalyzes a substrate-level phosphorylation.

Question 4 of 69

Which of the following molecules acts as a branch point between the synthesis of ketone bodies and cholesterol in animal bodies?

Mevalonate
D-β-hydroxybutyrate
Acetoacetate
β-hydroxy-β-methylglutaryl-CoA
Acetoacetyl-CoA

Question 5 of 69

Which of the following is true of fructose 1,6-bisphosphatase?

It involves dephosphorylation of fructose-6-phosphate.
It catalyzes a reaction that involves phosphate release.
It involves phosphorylation of glucose-6-phosphate.
It simply reverses the PFK reaction.
It requires ATP for catalysis.

Question 6 of 69

Which of the statements below about glucose is NOT true?

It makes 2 pyruvates in glycolysis.
It travels easily in the blood.
It is catabolized in gluconeogenesis.
It is stored in polymers in the body.
It is made from simple precursors.

Question 7 of 69

How does a cell overcome the energy barrier required for the aldolase reaction?

IT overcomes the energy barrier by deactivating the aldolase enzyme.
It overcomes the energy barrier by using the pushing and pulling process.
It overcomes the energy barrier by using cofactors.
It overcomes the energy barrier by removing the excess amounts of fructose-1,6-bisphosphate around the enzyme.
It overcomes the energy barrier by investing more and more ATPs.

Question 8 of 69

Which of the following enzymes is not a part of ketone body metabolism?

HMG-CoA synthetase
FBPase
Thiolase
β-hydroxybutyrate dehydrogenase
HMG-CoA lyase

Question 9 of 69

Which statement regarding the pentose phosphate pathway is TRUE?

It has multiple points of entry and endpoints connected to other pathways.
It is regulated by the products of the citric acid cycle.
It is involved in the oxidation of fatty acids.
It participates in the synthesis of NADP.
It has multiple inputs but only 1 output.

Question 10 of 69

Which is true of glucose-6-phosphatase?

It is found in the mitochondrion.
It produces glucose from fructose-6-phosphate directly.
It uses a phosphate in the reaction it catalyzes.
It is the reversal of the hexokinase reaction.
It is found in the endoplasmic reticulum.

Question 11 of 69

Which of the following is true of hexokinase in glycolysis?

ATP and glucose-6-phosphate are two products of the reaction it catalyzes.
It requires ATP to catalyze its reaction.
It catalyzes an isomerization.
It is the enzyme responsible for the third step in glycolysis.
It is a non-regulated enzyme of glycolysis.

Question 12 of 69

Which of the following is true about Triosephosphate isomerase (TPI)?

It is the rate limiting enzyme of gluconeogenesis.
It breaks down Glyceraldehyde-3-phosphate into three phosphates.
It catalyzes an irreversible reaction.
It requires lactate as a cofactor.
It converts the ketose dihydroxyacetone phosphate to the aldose glyceraldehyde-3-phosphate.

Question 13 of 69

Which of the following enzymes of the citric acid cycle is embedded in the inner mitochondrial membrane?

Aconitase
Malate dehydrogenase
Succinate dehydrogenase
α-ketoglutarate dehydrogenase
Isocitrate dehydrogenase

Question 14 of 69

Which statement regarding the 10 molecules in the pentose phosphate pathway is true?

They all are sugars or sugar derivatives.
They all are aldoses.
They all are intermediates in glycolysis.
They are all fatty acids.
They are all compound proteins.

Question 15 of 69

Which of the following is true of futile cycles?

Futile cycles produce excess NAD+.
Futile cycles consume energy without the net production of products.
Futile cycles are essential for catabolic processes.
Futile cycles are favored when cells are running low on energy.
Futile cycles are necessary to produce energy in the cell.

Question 16 of 69

Which of the following is true regarding phosphoglucoisomerase catalysis?

It performs a hydrolysis reaction.
The enzyme is a kinase.
Regulators of this reaction include G6P and F2,6BP.
G6P is converted to F6P using energy from ATP.
The reaction is readily reversible.

Question 17 of 69

Which of the following molecules participates in the release of oxygen from hemoglobin at the tissue or metabolically active cell sites?

1,3-bisphosphoglycerate
2-phosphoglycerate
2,3-bisphosphoglycerate
Phosphoenolpyruvate
3-phosphoglycerate

Question 18 of 69

How many oxidation reactions take place in the citric acid cycle?

Four
One
Five
Three
Two

Question 19 of 69

Deficiency of glucose-6-phosphate dehydrogenase can result in which of the following?

Anaphylaxis
Cachexia
Increased susceptibility to malarial parasites
Malnutrition
Anemia

Question 20 of 69

Which of the following enzymes is NOT matched correctly to the reaction it catalyzes?

Galactose-1-phosphate uridyl transferase: galactose-1-phosphate + UDP-glucose → UDP-galactose + glucose-1-phosphate
Galactose-1-phosphate uridyl transferase: glucose-6-phosphate + GDP-glucose
Lactase: lactose → glucose and galactose
UDP-galactose-4-epimerase: UDP-galactose → UDP-glucose

Question 21 of 69

Which statement below about phosphofructokinase (PFK) is NOT true?

It converts F6P to F1,6BP.
PFK is activated by high concentrations of ATP
PFK activity is inhibited by high concentrations of ATP.
PFK activity is activated by AMP.
It is an important regulatory enzyme for the glycolysis pathway.

Question 22 of 69

Which of the following is true of pyruvate kinase?

It must be regulated in order for gluconeogenesis to function.
It is continuously active in gluconeogenesis.
It is inactivated by fructose 1,6 bisphosphate.
It is activated by ATP and alanine.

Question 23 of 69

Which of the following enzymes participates in both the TCA cycle and the ETC?

Succinate dehydrogenase
Fumarase
α-Ketoglutarate dehydrogenase
Isocitrate dehydrogenase
Malate dehydrogenase

Question 24 of 69

Which statement regarding the reaction catalyzed by glucose-6-phosphate dehydrogenase is true?

It makes an individual more susceptible to malaria when deficient.
It is the rate-limiting step of the citric acid cycle.
It produces NADP.
It produces Acetyl-CoA.
It is the rate-limiting step of the pentose phosphate pathway (PPP).

Question 25 of 69

Which of the following statements about insulin is NOT true?

It stimulates the activity of phosphatase.
It stimulates the release of glucose from cells.
It stimulates the movement of glucose transporter-4 to the liver cell surface.
It stimulates the activity of glycogen synthase.
It inhibits the activity of phosphorylase kinase.

Question 26 of 69

Which of the following is true of pyruvate?

It uses NADH to produce acetaldehyde.
It is converted into acetyl-CoA when oxygen is limited.
It is made into lactate during fermentation.
It is an intermediate in the citric acid cycle.

Question 27 of 69

Which of the following statements is TRUE about thiolase?

It is important in fatty acid synthesis.
It catalyzes the formation of acetoacetyl-CoA from two acetyl-CoA molecules.
It catalyzes the removal of CoA-SH2.
It requires cAMP.

Question 28 of 69

Which statement regarding the reaction catalyzed by 6-phosphogluconate dehydrogenase is true?

It produces ATP.
Its deficiency is inherited in an x-linked pattern.
It produces NADP.
It is readily reversible.
It is the only decarboxylation of the pentose phosphate pathway (PPP).

Question 29 of 69

Which of the following is true of glycogen?

It has only alpha 1,4 bonds.
It has branches about every fifty glucose molecules.
It is a storage form for glucose in animals.
It is similar to cellulose in structure.
It helps plants to reduce glucose concentration.

Question 30 of 69

Which of the following hormones participates in the catabolism of glycogen?

Somatostatin
FS-hormone
Glucagon
Renalase
Insulin

Question 31 of 69

Which of the following statements about fermentation is incorrect?

It occurs when cells are short of oxygen.
It has different products in bacteria and humans.
It occurs when cells are short of NAD.
It requires acetaldehyde dehydrogenase.

Question 32 of 69

Which statement regarding the pentose phosphate pathway is TRUE?

It is regulated by the products of the citric acid cycle.
It participates in the synthesis of NADP.
It has multiple points of entry and endpoints connected to other pathways.
It has multiple inputs but only 1 output.
It is involved in the oxidation of fatty acids.

Question 33 of 69

Which statement regarding ribose-5-phosphate isomerase is true?

It produces NADPH.
It is involved in the synthesis of NAD.
The enzyme plays an essential role in lipid metabolism.
It catalyzes a reverse reaction important for protein metabolism.
It catalyzes the formation of ribose-5-phosphate.

Question 34 of 69

Which of the following is true regarding glycogen phosphorylase?

It uses phosphate from ATP to cleave glycogen.
It removes phosphate from glucose when it cleaves it from glycogen.
It puts a phosphate onto ADP or GDP when building glycogen.
It uses phosphate to create glucose-1-phosphate from glycogen.
It catalyzes the cleavage of a glucose molecule through a process called hydrolysis.

Question 35 of 69

Which one of the following signaling molecules promotes the breakdown of glycogen?

Na+
cGMP
Inositol triphosphate
ATP
cAMP

Question 36 of 69

Under aerobic conditions, what does the pyruvate get converted into?

2,3-bisphosphoglycerate
Ethanol
Acetyl CoA
Lactate
Acetaldehyde

Question 37 of 69

Which statement regarding the 10 molecules in the pentose phosphate pathway is true?

They all are aldoses.
They all are intermediates in glycolysis.
They are all compound proteins.
They all are sugars or sugar derivatives.
They are all fatty acids.

Question 38 of 69

Which statement regarding transketolase is true?

It catalyzes the transfer of 1-carbon units.
Its activity is decreased in vitamin B12 deficiency.
Its action is necessary for gluconeogenesis.
It requires thiamine pyrophosphate to function.
It doesn't require a coenzyme to function.

Question 39 of 69

Which of the following is true regarding phosphoglucomutase?

It needs ATP to catalyze the reaction.
It assists the debranching enzyme to remove glucose branches during glycogen breakdown.
It adds phosphate to cleave glucose from glycogen.
It catalyzes a non-reversible reaction.
It interconverts glucose-1-phosphate and glucose-6-phosphate.

Question 40 of 69

Which one of the following enzymes reverses the action of protein kinase A?

Phosphorylase a
Glycogen synthase
Adenylate cyclase
Phosphatase
Protein kinase B

Question 41 of 69

Which of the following molecules is central to most of the biological reactions in the cell during metabolism?

Glucose
Lipoamide
Acetyl CoA
Ethanol
Acetaldehyde

Question 42 of 69

Which statement regarding transaldolase is true?

It requires thiamine pyrophosphate (TPP).
It links the pentose phosphate pathway to the citric acid cycle.
It catalyzes the transfer of 2-carbon units.
It is an enzyme of the oxidative phase of the pentose phosphate pathway.
It catalyzes the transfer of 3-carbon units.

Question 43 of 69

Which of the following is true regarding debranching enzyme?

It converts 1,6 bonds to 1,4 bonds.
It makes 1,6 bonds.
It transfers part of a glucose branch of glycogen and releases free glucose from the 1-6 branch.
It catalyzes the reaction the make glucose-1,6-bisphosphate.
It converts 1,4 bonds to 1,6 bonds.

Question 44 of 69

Which one of the following enzymes is deactivated by epinephrine binding to the beta-adrenergic receptor?

glycogen synthase
phosphorylase a
phosphorylase kinase
protein kinase A
adenylate cyclase

Question 45 of 69

Which of the following amino acids is not synthesized from α-ketoglutarate of the citric acid cycle?

Glutamate
Tyrosine
Proline
Glutamine
Arginine

Question 46 of 69

Which condition results when transaldolase enzyme is deficient?

Liver cirrhosis
Reactive oxygen species sensitivity
Acute hemolytic disease
Malarial attacks
Anemia

Question 47 of 69

Which of the following is true of UDP glucose?

It is a substrate for glycogen phosphorylase.
It is made starting with UDP and glucose.
It is a substrate for branching enzyme.
It is the storage form of glucose in liver cells.
It is an activated intermediate with a high-energy bond.

Question 48 of 69

Which is true of phosphofructokinase (PFK)?

It has one binding site for ATP.
It utilizes Mg++ as a cofactor.
It catalyzes a reversible reaction.
The products of its catalysis are glucose-1,6-bisphosphate and ADP.
Its feedback is inhibited by AMP.

Question 49 of 69

Which of the following statements is not true regarding the citric acid cycle?

During anabolism of amino acids, the intermediates of the TCA cycle are used to synthesize the amino acids like glutamine, glutamate, proline, and arginine.
The oxaloacetate, a TCA cycle intermediate, acts as a precursor for the synthesis of aspartate, asparagine, methionine, and threonine.
In the absence of oxygen, the acetyl Co-A can’t enter the TCA cycle, so the yeast produces energy by converting pyruvate to ethanol.
The catabolic breakdown of amino acids produces the intermediates of the TCA cycle.
The citric acid cycle enables the yeast or a bacterial cell to get metabolic energy from acetyl Co-A in the absence of oxygen.

Question 50 of 69

Which compounds are the connectivity points for glycolysis or gluconeogenesis?

Ribose-5-phosphate and Glucose-6-phosphate
Xylulose-5-phosphate and Ribose-5-phosphate
Sedoheptulose-7-phosphate and erythrulose-4-phosphate.
Ribulose-5-phosphate and glucose-6-phosphate
Glyceraldehyde-3-phosphate and fructose-6-phosphate

Question 51 of 69

Which of the following statements regarding the regulation of glycogen metabolism is NOT true?

The G-protein is inactivated by the conversion of GTP to GDP.
Glycogen phosphorylase b is the active form of the enzyme.
GDP is released from the alpha subunit of the G-protein and replaced by GTP.
Glycogen synthase is inactivated by protein kinase a.
Phosphorylase kinase is activated by phosphorylation.

Question 52 of 69

Which of the following occurs during the aldolase reaction?

An accumulation of F1,6BP inhibits the enzyme.
The reaction is pushed forward by the accumulation of glyceraldehyde-3-phosphate.
The reaction is energetically very favorable.
The reaction can be reversed thanks to pulling and pushing.
One six-carbon molecule is split into two molecules of three carbons each.

Question 53 of 69

Which of the following statement is not true regarding the pyruvate dehydrogenase enzyme?

The enzyme pyruvate dehydrogenase converts the pyruvate to acetyl Co-A via decarboxylation in the presence of oxygen.
The E2 subunit of pyruvate dehydrogenase enzyme converts the TPP-acetaldehyde to acetyl-lipoamide, whereas the E3 subunit coverts the acetyl-lipoamide to acetyl-CoA.
The pyruvate dehydrogenase enzyme is a mitochondrial enzyme.
The pyruvate dehydrogenase enzyme converts the acetaldehyde to ethanol in the yeast cell in the absence of oxygen.
The pyruvate dehydrogenase enzyme is a very large multimeric complex composed of three subunits named E1, E2, and E3

Question 54 of 69

Which of the following is true regarding the breakdown of galactose?

It is combined with UDP-lactose.
It first must be recombined with glucose to form lactose.
It produces fructose.
It requires lactase.
It is converted into an intermediate in glycolysis.

Question 55 of 69

Which of the following is true of phosphodiesterase?

It catalyzes the formation of cAMP.
It inhibits the production of caffeine.
It is stimulated by caffeine.
It requires ATP.
It converts cAMP into AMP.

Question 56 of 69

Which of the following is true of glyceraldehyde-3-phosphate?

It is made in glycolysis from 1,3-bisphosphoglycerate (1,3 BPG).
It requires NADH to be oxidized.
It is the only molecule in glycolysis that gets oxidized.
It requires ATP to be oxidized.
It is converted to 1,3-bisphosphoglycerate using energy from ATP.

Question 57 of 69

Which of the following is not correctly matched?

Succinyl-CoA — used to make heme
Citrate — allosteric effector for some enzymes
α-Ketoglutarate — used in amino acid and nitrogen metabolism
Malate — generates FADH2 when it is converted to oxaloacetate
Fumarate — important in nucleotide metabolism

Question 58 of 69

Which of the following statements about the metabolism of fructose is NOT true?

Fructokinase needs Magnesium as a cofactor.
It bypasses regulatory enzymes in glycolysis.
It is inhibited by excess glucose.
It can bypass phosphofructokinase (PFK).
It ultimately produces glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.

Question 59 of 69

Which enzyme is activated when higher concentrations of AMP are present?

Pyruvate kinase
Nuclease
FBPase
PFK
Hexokinase

Question 60 of 69

Which of the following is true of the conversion of 1,3-bisphosphoglycerate (1,3 BPG) to 3-phosphoglycerate?

This reaction is not very energetically favorable.
This reaction is catalyzed by phosphoglycerate mutase.
This reaction is the only oxidation reaction in glycolysis.
This reaction is called a substrate-level phosphorylation.
This reaction is how most ATP is formed in the cell.

Question 61 of 69

Which of the following is correct regarding the energy output per cycle of the citric acid cycle?

1 NADH2, 3 FADH2, and 3 ATP
1 NADH2, 3 FADH2, and 1 ATP
1 NADH2, 1 FADH2, and 1 ATP
1 NADH2, 1 FADH2, and 3 GTP
3 NADH, 1 FADH2, and 1 GTP

Question 62 of 69

Which of the following is true of gluconeogenesis?

It needs one pyruvate molecule to make one glucose molecule.
It occurs in most cells of the body.
It occurs solely in the mitochondrion.
It bypasses three enzyme reactions of glycolysis.
It starts with acetyl-CoA.

Question 63 of 69

Which enzyme is activated when higher concentrations of citrate are present?

Pyruvate kinase
FBPase
Nuclease
PEPCK
Hexokinase

Question 64 of 69

Which of the following is true of 2,3-bisphosphoglycerate (2,3 BPG)?

It can be produced from 1,3-BPG and 3-phosphoglycerate.
It binds to myoglobin.
It is a glycolysis endproduct.
It favors uptake of oxygen by oxygen-binding proteins.

Question 65 of 69

Which of the following enzymes are unique to the glyoxylate cycle?

Malate dehydrogenase
Isocitrate lyase
Citrate synthase
Succinate dehydrogenase
Malate synthase

Question 66 of 69

Which of the following is true of the reaction catalyzed by pyruvate carboxylase?

It is the backward reaction of pyruvate kinase.
It is a reaction that produces phosphoenolpyruvate (PEP).
The reaction takes place in the cytoplasm.
It is a reaction that requires biotin.
It is a reaction that uses GTP.

Question 67 of 69

What linkage is formed by branching enzyme in glycogen synthesis?

β(1→6) linkage
γ(1→6) linkage
α(1→6) linkage
α(1→4) linkage
β(1→4) linkage

Question 68 of 69

Which of the following is true of phospoenolpyruvate (PEP)?

It requires ATP to be produced.
It is made from 2-phosphoglycerate by addition of water.
It is a stimulator of aldolase.
It is a very high-energy compound.

Question 69 of 69

Which of the following statements is not correct regarding the glyoxylate cycle?

In the glyoxylate cycle, there is no net production of CO2 molecules
The glyoxylate pathway helps the bacterial cell to carry out the gluconeogenesis by using Acetyl-CoA as a carbon source
The glyoxylate pathway is found in plants and bacteria only
The glyoxylate cycle is exclusive to the muscle cells as it helps in the synthesis of glucose from the acetyl-CoA during contraction process
The glyoxylate cycle helps to bypass the decarboxylation steps of the citric acid cycle

Carbohydrates Metabolism Biochemistry 2023

Carbohydrates Metabolism Biochemistry 2023

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