Ilsa West
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Quiz on Biochem Exam 2 Oldies Questions, created by Ilsa West on 10/06/2014.

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Biochem Exam 2 Oldies Questions

Biochem Exam 2 Oldies Questions

Question 1 of 120

1

A recent study found that polyQ aggregation can interfere with the celarance of misfolded proteins in the cytosol. PolyQ is a serial repeat of _________ residues.

Select one of the following:

  • arginine

  • glycine

  • glutamate

  • ubiquitin

  • glutamine

Explanation

Question 2 of 120

1

An enzyme binds its substrate under optimal conditions. Upon this binding, which of the following will subsequently occur?

Select one of the following:

  • an enzyme-substrate complex is produced

  • binding of the substrate causes a conformational change in the enzyme

  • enzyme-substrate complex is converted to an enzyme-product complex

  • all of the above will occur

  • none of the above will occur

Explanation

Question 3 of 120

1

An enzyme functions by _________.

Select one of the following:

  • increasing the free energy of activation

  • decreasing the free energy of the reactants

  • increasing the free energy of the product

  • all of the above

  • none of the above

Explanation

Question 4 of 120

1

One graphs a Lineweaver-Burk plot of an enzymatic reaction, then of the same reaction in the presence of an inhibitor. The plot of the second reaction shows that the X-intercept has moved closer to zero. This means that _________.

Select one of the following:

  • the inhibitor is noncompetitive

  • the inhibitor must lower the Vmax

  • the inhibitor binds reversibly to the same site that the substrate would normally occupy

  • all of the above

  • none of the above

Explanation

Question 5 of 120

1

One graphs a Lineweaver-Burk plot of an enzymatic reaction, then of the same reaction in the presence of an inhibitor. The second plot shows that the Y-intercept has shifted upwards. This means that _________.

Select one of the following:

  • The inhibitor is competitive

  • The inhibitor lowers the Vmax

  • The inhibitor binds to the active site of the enzyme

  • All of the above

  • None of the above

Explanation

Question 6 of 120

1

An enzyme follows Michaelis-Menten kinetics. The amount of substrate is twice the value of Km. This means that the initial velocity (Vo) is equal to ________ Vmax.

Select one of the following:

  • 2 times

  • 1/2

  • 2/3

  • 1/3

  • 4 times

Explanation

Question 7 of 120

1

Human dihydrofolate reductase can be competitively inhibited by _______.

Select one of the following:

  • sulfanilamide

  • penicillin

  • methotrexate

  • acyclovir

  • neuraminidase

Explanation

Question 8 of 120

1

One is graphing the initial reaction velocity (Vo) against substrate concentration of an allosteric enzyme This graph would yield _________.

Select one of the following:

  • a straight line, with its intercept on the X-axis representing the Vmax

  • a hyperbole, with the asymptote representing the Km

  • - a straight line, with its intercept on the X-axis representing the Vmax
    - a hyperbole, with the asymptote representing the Km

  • None of the above

Explanation

Question 9 of 120

1

________ and __________ are enzymatic activities of a single protein which is cleaved into two functional subunits that remain associated in the cell membrane.

Select one of the following:

  • lactase, trehalase

  • sucrase, isomaltase

  • lactase, sucrase

  • trypsinogen, trypsin

  • maltase, isomaltase

Explanation

Question 10 of 120

1

_______ is a salivary endoglycosidase that hydrolyzes glycosidic bonds in cell walls.

Select one of the following:

  • Alpha-amylase

  • dextrin

  • lysosome

  • lysozyme

  • peptidoglycan

Explanation

Question 11 of 120

1

Which of the following is the mechanism by which enteropeptidase converts trypsinogen to trypsin?

Select one of the following:

  • it adds a phosphate to the trypsinogen

  • it cleaves a phosphate from the trypsinogen

  • it adds six amino acids to the trypsinogen

  • it removes six amino acids from the trypsinogen

  • it functions by competitive inhibition of trypsinogen

Explanation

Question 12 of 120

1

Which of the following best describes maltose?

Select one of the following:

  • a single monosaccharide

  • a disaccharide composed of fructose and glucose

  • a disaccharide composed of galactose and glucose

  • a disaccharide composed of two molecules of galactose

  • a disaccharide composed of two molecules of glucose

Explanation

Question 13 of 120

1

Which of the following is (are) resistant to salivary amylase?

Select one of the following:

  • lactose

  • sucrose

  • - lactose
    - sucrose

  • none of the above

Explanation

Question 14 of 120

1

Undigested lactose can be metabolized into hydrogen gas by ______.

Select one of the following:

  • intestinal mucosal cells

  • oral mucosal cells

  • intestinal flora

  • liver cells

  • glands of the pancreas

Explanation

Question 15 of 120

1

A molecule is designed to bear resemblance, in both structure and polarity, to the transition state of a specific substrate associated with a specific reaction. This molecule is added to an enzymatic reaction involving this substrate. The most likely effect of the addition of the molecule to the reaction would be ___________.

Select one of the following:

  • an increase in the Vmax

  • an increase in the Km

  • a decrease in the Vmax

  • a decrease in the Km

  • a generalized allosteric effect

Explanation

Question 16 of 120

1

Heparin can act as a _____ of anti-thrombin III.

Select one of the following:

  • competitive inhibitor

  • irreversible, non-specific competitive inhibitor

  • specific non-competitive inhibitor

  • none of the above

Explanation

Question 17 of 120

1

Lactase is _______.

Select one of the following:

  • an isozyme of maltase

  • a mucosal cell membrane-bound disaccharidase

  • synthesized as a pancreatic zymogen

  • maximally active in the large intestine

  • capable of cleaving the alpha (1-->6) bond in lactose

Explanation

Question 18 of 120

1

Mucopolysaccharidoses are directly associated with _____.

Select one of the following:

  • an increased rate of synthesis of glycoproteins

  • a decreased rate of synthesis of glycosaminoglycans

  • an increased rate of degradation of glycoproteins

  • a decreased rate of degradation of glycoproteins

  • none of the above

Explanation

Question 19 of 120

1

Which of the following statement(s) about glycosaminoglycans is (are) TRUE?

Select one of the following:

  • the bear a net positive charge

  • they are usually bound to the core protein through a glycosidic N-linkage

  • the amount of protein in a proteoglycan generally exceeds 90%

  • the D-glucuronic acid and the L-iduronic acid in the glycosaminoglycan contain carboxyl groups that are negatively charged at physiological conditions

  • the amino sugar in the glycosaminoglycan can often consist of a glucose covalently bound to an asparagine or a glutamine

Explanation

Question 20 of 120

1

Which of the following statement(s) about heparin is (are) TRUE?

Select one of the following:

  • heparin is synthesized only by hepatocytes

  • heparin is a ubiquitous component of cell surfaces

  • heparin is located inside mast cell that line the arteries, especially of the liver, lungs and skin

  • - heparin is synthesized only by hepatocytes
    - heparin is a ubiquitous component of cell surfaces
    - heparin is located inside mast cell that line the arteries, especially of the liver, lungs and skin

  • none of the above

Explanation

Question 21 of 120

1

Heparin ________ anti-thrombin III, ultimately ______ the process of coagulation.

Select one of the following:

  • competitively inhibiting, inhibiting

  • irreversibly inhibiting, inhibiting

  • activates, activating

  • activates, inhibiting

  • proteolytically cleaves, activating

Explanation

Question 22 of 120

1

___________ is the most abundant glycosaminoglycan found in body, found in the aorta, ligaments, tendons

Select one of the following:

  • heparan sulfate

  • chondroitin 4- and 6- sulfates

  • hyaluronic acid

  • keratan sulfates

  • all of the above

Explanation

Question 23 of 120

1

______ is found in bacteria.

Select one of the following:

  • heparan sulfate

  • chondroitin 4- and 6- sulfates

  • hyaluronic acid

  • keratan sulfates

  • all of the above

Explanation

Question 24 of 120

1

_______ is ubiquitous component of cell surfaces.

Select one of the following:

  • heparan sulfate

  • chondroitin 4- and 6- sulfates

  • hyaluronic acid

  • keratan sulfates

  • all of the above

Explanation

Question 25 of 120

1

I-cell disease is generally caused by a defect in the gene that codes for

Select one of the following:

  • a specific lysosomal enzyme

  • the glycoprotein that codes for mannose 6-phosphate

  • the mannose 6-phosphate receptor in the Golgi

  • the enzyme that phosphorylates mannose residues

  • the mannose 6-phosphate receptor in the lysosome

Explanation

Question 26 of 120

1

Which of the following is (are) NOT (a) glycoprotein(s)?

Select one of the following:

  • serum albumin

  • erythropoietin

  • mucin

  • - serum albumin
    - erythropoietin
    - mucin

  • none of the above are glycoproteins

Explanation

Question 27 of 120

1

Medication X is a specific inhibitor of a certain PDE (phosphodiesterase). One would anticipate that the major direct effect of X would be _________.

Select one of the following:

  • a decrease of the amount of cAMP

  • an increase in the amount of cAMP

  • a decrease in the amount and the enzymatic activity of the protein being phosphorylated by the cAMP independent kinase

  • an increase in the amount of adenylyl cyclase synthesized by the transmembrane receptors

  • a decrease in the amount of protein phosphatase being synthesized

Explanation

Question 28 of 120

1

Which of the following statements about the cAMP second messenger system is (are) TRUE?

Select one of the following:

  • the seven transmembrane helices will directly hydrolyze GTP after the binding of the ligand

  • the activated adenylyl cyclase will hydrolyze GTP to yield the requisite energy for activation of the bound ligand

  • The alpha subunit of the Gs protein can hydrolyze GTP to GDP

  • cAMP-dependent protein kinase A will hydrolyze GTP to GDP

  • all of the above are true

Explanation

Question 29 of 120

1

Liver glucokinase exhibits a _____ Km and a _________ Vmax relative to brain hexokinase

Select one of the following:

  • higher, higher

  • lower, lower

  • higher, lower

  • lower, higher

Explanation

Question 30 of 120

1

2 Acetyl-CoA + 2 oxaloacetate --> 4 CO2 + 6 NADH + 2 FADH2 + 2 ATP + 2 oxaloacetate

Select one of the following:

  • the TCA cycle for one molecule of glucose

  • reaction catalyzed by cytochrome oxidase

  • reaction is inhibited by oligomycin

  • reaction catalyzed by pyruvate dehydrogenase

  • ubiquinone

Explanation

Question 31 of 120

1

Pyruvate + NAD+ + CoA-SH --> Acetyl CoA + NADH + H+ + CO2

Select one of the following:

  • the TCA cycle for one molecule of glucose

  • reaction catalyzed by cytochrome oxidase

  • reaction is inhibited by oligomycin

  • reaction catalyzed by pyruvate dehydrogenase

  • ubiquinone

Explanation

Question 32 of 120

1

4 H+ + O2 + 4 Cyt C-Fe2+ --> 2 H2O + 4 Cyt.-C-Fe3+

Select one of the following:

  • the TCA cycle for one molecule of glucose

  • the reaction catalyzed by cytochrome oxidase

  • reaction is inhibited by oligomycin

  • reaction catalyzed by pyruvate dehydrogenase

  • ubiquinone

Explanation

Question 33 of 120

1

ATP Synthase

Select one of the following:

  • the TCA cycle for one molecule of glucose

  • reaction catalyzed by cytochrome oxidase

  • reaction is inhibited by oligomycin

  • reaction catalyzed by pyruvate dehydrogenase

  • ubiquinone

Explanation

Question 34 of 120

1

Coenzyme Q

Select one of the following:

  • the TCA cycle for one molecule of glucose

  • reaction catalyzed by cytochrome oxidase

  • reaction is inhibited by oligomycin

  • reaction catalyzed by pyruvate dehydrogenase

  • ubiquinone

Explanation

Question 35 of 120

1

Dinitrophenol is an uncoupler of oxidative phosphorylation. Its mechanism involves _____.

Select one of the following:

  • the inhibition of NADH dehydrogenase

  • the activation of Coenzyme Q

  • the inhibition of ATP synthase

  • allowing for the leakage of protons across the inner membrane of the the mitochondria

  • the reduction of NADH at complex I

Explanation

Question 36 of 120

1

The condensation of the acetyl group of acetyle CoA with oxaloacetate in the TCA cycle can be decreased by _______.

Select one of the following:

  • a high ratio of NADH to NAD+

  • a high ratio of GDP to GTP

  • a high concentration of AMP

  • Thymine

Explanation

Question 37 of 120

1

Which of the following characterize(s) glycoproteins?

Select one of the following:

  • they have diglucosyl serial repeats

  • the only amino acids to which the oligosaccharide can possibly link are serine or threonine

  • - they have diglucosyl serial repeats
    - the only amino acids to which the oligosaccharide can possibly link are serine or threonine

  • none of the above

Explanation

Question 38 of 120

1

The synthesis of branched oligosaccharides on dolichol pryophosphate and the transfer of the oligosaccharide to the growing polypeptide chain is associated with

Select one of the following:

  • N-linked glycoproteins

  • O-linked glycoproteins

  • - N-linked glycoproteins
    - O-linked glycoproteins

  • none of the above

Explanation

Question 39 of 120

1

Which of the following is not a glycoprotein?

Select one of the following:

  • heparin

  • collagen

  • Immunoglobulin IgG

  • Mucin

  • erythrocyte blood group antigens

Explanation

Question 40 of 120

1

Which of the following is a sialoglycoprotein that contribute significantly to the negative charge of the outer erythrocyte membrane?

Select one of the following:

  • neuraminidase

  • hemaglutinin

  • gp120

  • CD 4

  • Glycophorin

Explanation

Question 41 of 120

1

Hydrolysis of cAMP to 5' AMP

Select one of the following:

  • phosphodiesterase

  • adenylyl cyclase

  • protein phosphatase

  • protein kinase A

Explanation

Question 42 of 120

1

Glucokinase has a Km for glucose of ________ and ______ directly by glucose 6-phosphate.

Select one of the following:

  • about 0.1 mM, is inhibited

  • about 0.1 mM, is not inhibited

  • about 10 mM, is inhibited

  • about 10 mM, is not inhibited

Explanation

Question 43 of 120

1

Hexokinase has a Km for glucose of _______ and ____________ by glucose 6-phosphate

Select one of the following:

  • about 0.1 mM, is inhibited

  • about 0.1 mM, is not inhibited

  • about 10 mM, is inhibited

  • about 10 mM, is not inhibited

Explanation

Question 44 of 120

1

An elevated ratio of ____________, __________ the formation of fructose 2,6 bisphosphate. Fructose 2,6 bisphosphate subsequently promotes the formation of fructose 1,6 bisphosphate.

Select one of the following:

  • Insulin to glucagon, promotes

  • Insulin to glucagon, inhibits

  • Glucagon to insulin, promotes

  • G proteins to insulin receptors, promotes

  • all of the above

Explanation

Question 45 of 120

1

______ can lead directly to ______, which can result in an increase in lactate.

Select one of the following:

  • Impaired mitochondrial function, increased oxidation of NADH

  • Impaired mitochondrial function, decreased oxidation of NADH

  • Impaired glycolysis, increased reduction of NAD+

  • Impaired glycolysis, decreased oxidation of NADH

Explanation

Question 46 of 120

1

How many molecules of O2 are reduced in order to catabolize 1 molecule of glucose to lactate?

Select one of the following:

  • 0

  • 1

  • 2

  • 10

  • 36

Explanation

Question 47 of 120

1

Uncouplers of oxidative phosphorylation

Select one of the following:

  • uncouple the transfer of electrons from the reduction of oxygen

  • uncouple the transfer of electrons from the synthesis of ATP

  • inhibit the transfer of electrons along the length of the electron transport chain

  • inhibit the entry of coenzymes into the mitochondria

  • competitively inhibit cytochrome oxidase

Explanation

Question 48 of 120

1

The TCA cycle is

Select one of the following:

  • anabolic

  • catabolic

  • both anabolic and catabolic

  • none of the above

Explanation

Question 49 of 120

1

A single glucose molecule enters a cell. This cell has totally dysfunctional mitochondria. What would be the expected net yield of ATP molecules generated by this one molecule of glucose?

Select one of the following:

  • 1

  • 2

  • 4

  • 8

  • 36-38

Explanation

Question 50 of 120

1

Which of the following is a site-specific inhibitor of the electron transport chain?

Select one of the following:

  • cyanide (CN`)

  • arsenic

  • oligomycin

  • thermogenin

  • ubiquinone

Explanation

Question 51 of 120

1

_________ activate(s) the protein kinase that phosphorylates the pyruvate dehydrogenase complex, thusly inactivating this complex.

Select one of the following:

  • AMP

  • Calcium

  • ATP

  • all of the above activate the protein kinase that....

  • None of the above activate the protein kinase that.....

Explanation

Question 52 of 120

1

How many water molecules are produced for every FADH2 molecule that is oxidized

Select one of the following:

  • 0

  • 1

  • 1.5

  • 2

  • 3

Explanation

Question 53 of 120

1

Which of the following statement(s) about mitochondria is (are) correct?

Select one of the following:

  • The mitochondrial genome is approximately the size of the nuclear genome

  • The mitochondrial genome is not susceptible to mutations

  • the mitochondrial genome is circular

  • the mitochondrial genome codes for about 25,000 genes

  • there are no known human genetic diseases associated with the mitochondrial gene

Explanation

Question 54 of 120

1

Which of the following glucose transporters are involved in the diffusion of glucose from a high concentration to a low concentration?

Select one of the following:

  • GLUT-1

  • GLUT-2

  • GLUT-3

  • GLUT-4

  • all of the above are involved in the diffusion of glucose from a high concentration to a low concentration

Explanation

Question 55 of 120

1

GLUT-4 is under the influence of ______, and is abundant in _______ tissue.

Select one of the following:

  • Insulin, skeletal muscle and adipose

  • Glucagon, skeletal muscle and adipose

  • glucagon, brain

  • insulin, mucosal

  • pyruvate kinase, pancreatic

Explanation

Question 56 of 120

1

ATP --> cAMP + PPi corresponds to which enzyme?

Select one of the following:

  • phosphodiesterase

  • adenylyl cyclase

  • protein phosphatase

  • protein kinase A

Explanation

Question 57 of 120

1

Phosphorylation of protein substrate in presence of hydrolysis of ATP to ADP corresponds to which enzyme?

Select one of the following:

  • phosphodiesterase

  • adenylyl cyclase

  • protein phosphatase

  • protein kinase A

Explanation

Question 58 of 120

1

Dephosphorylation of protein corresponds to which enzyme?

Select one of the following:

  • phosphodiesterase

  • adenylyl cyclase

  • protein phosphatase

  • protein kinase A

Explanation

Question 59 of 120

1

Hydrolysis of cAMP to 5' AMP corresponds to which enzyme?

Select one of the following:

  • phosphodiesterase

  • adenylyl cyclase

  • protein phosphatase

  • protein kinase A

Explanation

Question 60 of 120

1

Which of the following processes is associated with the degradation of dermatan sulfate?

Select one of the following:

  • cellular ingestion of dermatan sulfate by phagocytosis

  • formation of a vesicle containing dermatan sulfate

  • fusion of vesicle containing dermatan sulfate with lysosome

  • all of the above are associated with the degradation of dermatan sulfate

  • none of the above are associated with the degradation of dermatan sulfate

Explanation

Question 61 of 120

1

Which of the statements about heparin is/are correct?

Select one of the following:

  • Heparain competitively inhibits anti-thrombin III, thusly enhancing the formation of clots

  • Heparin noncompetitively inhibits anti-thrombin III, thusly enhancing the formation of clots

  • Heparin competitively inhibits anti-thrombin III, thusly inhibiting the formation of clots

  • Heparin noncompetitively inhibits anti-thrombin III, thusly inhibiting the formation of clots

  • Heparin activates anti-thrombin III, thusly inhibiting the formation of clots

Explanation

Question 62 of 120

1

Mucopolysaccharidoses are characterized by defects associated with enzymes involved with which of the following?

Select one of the following:

  • degradation of core protein

  • sulfation (addition of sulfate groups) of carbohydrate chain

  • formation of carbohydrate chain

  • - degradation of core protein
    - sulfation (addition of sulfate groups) of carbohydrate chain
    - formation of carbohydrate chain

  • none of the above

Explanation

Question 63 of 120

1

Glycophorin is

Select one of the following:

  • a virally encoded glycoprotein associated with the release of the influenza virus from the host cell

  • a virally encoded glycoprotein associated with the binding of the influenza virus to the host cell

  • a sialoglycoprotein on the erythrocyte membrane

  • an intracellular chaperonin found inside all human cells

  • the fetal isoform of an adult plasma glycoprotein

Explanation

Question 64 of 120

1

which of the following statements about glycoprotein storage diseases is/are correct?

Select one of the following:

  • the diseases can result in the accumulation of oligosaccharide fragments inside the lysosomes

  • these diseases are caused by defects in different exoenzymes

  • I-cell disease is classified as a glycoprotein storage disease

  • - the diseases can result in the accumulation of oligosaccharide fragments inside the lysosomes
    - these diseases are caused by defects in different exoenzymes
    - I-cell disease is classified as a glycoprotein storage disease

  • none of the above are correct

Explanation

Question 65 of 120

1

Which of the following statement(s) about ATP is/are correct?

Select one of the following:

  • the energy released from the hydrolysis of ATP can be utilized for the polymerization of microtubules

  • the standard free energy of hydrolysis of ATP is +7.3 kcal/mol

  • Many intra-cellular exergonic (energy yielding) reactions are coupled to the hydrolysis of ADP to AMP, thusly accelerating the reaction to a physiologically viable speed

  • - Which of the following statement(s) about ATP is/are correct?
    - the standard free energy of hydrolysis of ATP is +7.3 kcal/mol
    - Many intra-cellular exergonic (energy yielding) reactions are coupled to the hydrolysis of ADP to AMP, thusly accelerating the reaction to a physiologically viable speed

  • none of the above are correct

Explanation

Question 66 of 120

1

A Gi protein, activated by the binding of a hormone to the membrane receptor, would DIRECTLY inhibit

Select one of the following:

  • the formation of cAMP from ATP

  • the formation of ADP from ATP

  • the binding of the ligand to the membrane receptor

  • the hydrolysis of cAMP by phosphodiesterase

  • the hydrolysis of GTP to GDP

Explanation

Question 67 of 120

1

cAMP is formed by the enzymatic action of _____ and hydrolyzed by the enzymatic action of _____.

Select one of the following:

  • protein kinase A, ATPase

  • adenylate kinase, protein phosphatase

  • adenylate kinase, cAMP phosphodiesterase

  • adenylyl cyclase, cAMP phosphodiesterase

  • protein kinase A, protein phosphatase

Explanation

Question 68 of 120

1

Which of the following statement(s) characterize(s) all GLUT's (glucose transporters)

Select one of the following:

  • the number of all active GLUT molecules is increased by insulin

  • the only monosaccharide transported by all GLUT's is glucose

  • while all GLUT's display very high affinity to glucose, they can never approach saturation point

  • - the number of all active GLUT molecules is increased by insulin
    - the number of all active GLUT molecules is increased by insulin
    - while all GLUT's display very high affinity to glucose, they can never approach saturation point

  • none of the above characterize all GLUT's

Explanation

Question 69 of 120

1

Glycolysis occurs in the ______.

Select one of the following:

  • rough endoplasmic reticulum

  • golgi apparatus

  • lysosome

  • all of the above

  • none of the above

Explanation

Question 70 of 120

1

_______ levels of glucagon and _____ levels of insulin cause an increase in the overall rate of glycolysis.

Select one of the following:

  • decreased, elevated

  • decreased, decreased

  • elevated, decreased

  • elevated, elevated

Explanation

Question 71 of 120

1

______ levels of glucagon and ______ levels of insulin cause an increase in the overall rate of gluconeogenesis.

Select one of the following:

  • decreased, elevated

  • decreased, decreased

  • elevated, decreased

  • elevated, elevated

Explanation

Question 72 of 120

1

Glucokinase displays a _______ relative to hexokinase

Select one of the following:

  • higher Vmax

  • lower Km

  • greater degree of inhibition by glucose 6 phosphate

  • - higher Vmax
    - lower Km
    - greater degree of inhibition by glucose 6 phosphate

  • none of the above

Explanation

Question 73 of 120

1

Which of the following statement(s) about the SGLT (sodium-dependent-glucose transporter) is/are correct?

Select one of the following:

  • the SGLT transports glucose from a high concentration inside the intestinal lumen to a low concentration inside the intestinal epithelial cell

  • the SGLT transports sodium from a high concentration inside the intestinal epithelial cell to a low concentration inside the blood

  • the SGLT transports glucose from a low concentration inside the portal circulation to a high concentration inside the intestinal lumen

  • the SGLT transports glucose from a low concentration inside the intestinal lumen to a higher concentration inside the intestinal epithelial cell

  • the SGLT transports sodium from a low concentration inside the intestinal lumen to a higher concentration inside the intestinal epithelial cell

Explanation

Question 74 of 120

1

Which of the following statements about glycosaminoglycans (GAG's) is/are true?

Select one of the following:

  • they tend to be extremely hydrophobic

  • they are linked to molecules of dolichol through a noncovalent bond

  • they generally are heteropolymers consisting of alternating glucose and fructose molecules

  • - they tend to be extremely hydrophobic
    - they are linked to molecules of dolichol through a noncovalent bond
    - they generally are heteropolymers consisting of alternating glucose and fructose molecules

  • none of the above are true

Explanation

Question 75 of 120

1

Which of the following class of GAG's functions only in an intracellular manner?

Select one of the following:

  • hyaluronic acid

  • dermatan sulfate

  • keratan sulfate

  • heparan sulfate

  • heparin

Explanation

Question 76 of 120

1

The core protein of chondroitin sulfate is synthesized on and enters the _____ prior to its being glycosylated.

Select one of the following:

  • rough endoplasmic reticulum

  • lysosome

  • golgi apparatus

  • cytosol

  • smooth endoplasmic reticulum

Explanation

Question 77 of 120

1

Which of the following statements about heparin is true?

Select one of the following:

  • heparin is a competitive inhibitor of anti-thrombin III

  • heparin is a noncompetitive inhibitor of anti-thrombin III

  • heparin is an activator of anti-thrombin III

  • heparin is a serpin (serine protease inhibitor)

  • heparin is often administered in order to promote coagulation

Explanation

Question 78 of 120

1

Mucopolysaccharidoses are characterized by a genetic defect of enzymes involved in?

Select one of the following:

  • the elongation of disaccharides constituting the GAG's

  • the synthesis of the proteoglycan monomers

  • lysosomal hydrolysis

  • sulfation (addition of sulfates)

  • synthesis of glucuronic acid

Explanation

Question 79 of 120

1

Alpha 1-antitrypsin ____________.

Select one of the following:

  • is synthesized as alpha 1-antitrypsinogen in the alveoli of the lung

  • is primarily synthesized and secreted by the liver

  • Functions physiologically by specifically inhibiting neutrophil trypsin, the production of which can be induced by the intake of toxic gases associated with cigarette smoke

  • functions physiologically by specifically inhibiting the collagenase secreted by bacteria in the vicinity of the lung

  • functions primarily in the inhibition of pancreatic trypsin

Explanation

Question 80 of 120

1

Alpha 1-antitrypsin deficiency can be treated by _________.

Select one of the following:

  • intravenous administration of alpha 1-antitrypsin

  • dialysis of plasma to remove elastase

  • enzyme therapy utilizing liver-specific hydrolases

  • oral administration of a variety of different serpins (serine protease inhibitors)

Explanation

Question 81 of 120

1

Which of the following statement(s) about ATP is (are) true?

Select one of the following:

  • ATP is constantly being consumed and regenerated by the human body

  • ATP can be consumed by biosynthetic reactions

  • ATP can be regenerated by the oxidation of calorie-yielding foodstuffs

  • - ATP is constantly being consumed and regenerated by the human body
    - ATP can be consumed by biosynthetic reactions
    - ATP can be regenerated by the oxidation of calorie-yielding foodstuffs

  • none of the above are true

Explanation

Question 82 of 120

1

Which of the following statement(s) about G proteins is (are) true?

Select one of the following:

  • The G protein receptor contains both an intracellular and an extracellular domain

  • When the binding hormone is no longer present, the GTP on the alpha subunit is hydrolyzed to GDP

  • adenylyl cyclase can be activated by the alpha subunit bound to GTP

  • - The G protein receptor contains both an intracellular and an extracellular domain
    - When the binding hormone is no longer present, the GTP on the alpha subunit is hydrolyzed to GDP
    - adenylyl cyclase can be activated by the alpha subunit bound to GTP

  • none of the above are true

Explanation

Question 83 of 120

1

Drug D inhibits a specific cyclic nucleotide phosphodiesterase. The most immediate effect of this drug would be _____.

Select one of the following:

  • an accumulation of the G protein receptor proteins

  • a decrease in the number of G protein receptor proteins

  • an accumulation of Cyclic AMP molecules

  • a decrease in the number of Cyclic AMP molecules

  • a decrease in the number of Cyclic AMP-independent protein kinase C molecules

Explanation

Question 84 of 120

1

Each catalytic subunit of protein kinase A, under physiological conditions _____________.

Select one of the following:

  • binds one molecule of cAMP

  • binds two molecules of cAMP

  • binds four molecules of cAMP

  • all of the above

  • none of the above

Explanation

Question 85 of 120

1

GLUT-2 serves as a glucose sensor in the beta cells of the pancreas. GLUT-2 is a ________ transporter.

Select one of the following:

  • high capacity, high affinity

  • high capacity, low affinity

  • low capacity, high affinity

  • low capacity, low affinity

Explanation

Question 86 of 120

1

(1) No GLUT can, under physiological conditions, transport glucose out of a cell. (2) Every GLUT is under the influence of insulin.

Select one of the following:

  • The first statement is true. The second statement is true.

  • The first statement is true. The second statement is false.

  • The first statement is false. The second statement is true.

  • The first statement is false. The second statement is false.

Explanation

Question 87 of 120

1

Which of the following statement(s) about the SGLT (sodium-dependent glucose transporter) associated with the epithelial cells of the intestine is (are) true?

Select one of the following:

  • The entry of glucose is coupled to the concentration gradient of sodium, which is co-transported into the cell

  • sodium and glucose both exit the cell through the agency of the same GLUT

  • - The entry of glucose is coupled to the concentration gradient of sodium, which is co-transported into the cell
    - sodium and glucose both exit the cell through the agency of the same GLUT

  • none of the above

Explanation

Question 88 of 120

1

Glucokinase has a _________ relative to hexokinase.

Select one of the following:

  • Higher Km, lower Vmax

  • Higher Km, higher Vmax

  • Lower Km, lower Vmax

  • Lower Km, higher Vmax

Explanation

Question 89 of 120

1

Type I (more aerobic) muscle fibers _____________ relative to the Type II (less aerobic) fibers

Select one of the following:

  • have more myoglobin

  • produce less lactic acid

  • - have more myoglobin
    - produce less lactic acid

  • none of the above

Explanation

Question 90 of 120

1

Which of the following statement(s) about pyruvate kinase is (are) true?

Select one of the following:

  • the product of the glycolytic reaction catalyzed by pyruvate kinase is lactate

  • mutations of the pyruvate kinases gene can result in anemia

  • the glycolytic reaction catalyzed by pyruvate kinase is extremely endergonic

  • - the product of the glycolytic reaction catalyzed by pyruvate kinase is lactate
    - mutations of the pyruvate kinases gene can result in anemia
    - the glycolytic reaction catalyzed by pyruvate kinase is extremely endergonic

  • none of the above are true

Explanation

Question 91 of 120

1

The enzymatic deficiency associated with I-cell disease results in __________.

Select one of the following:

  • a single defective N-linked glycoprotein that normally functions as a lysosomal enzyme

  • a single defective O-linked glycoprotein that normally functions as a lysosomal enzyme

  • multiple defective N-linked glycoproteins that normally function as lysosomal enzymes

  • multiple defective N-linked glycoproteins that normally function as transmembrane proteins

  • multiple defective O-linked glycoproteins that normally function as transmembrane proteins

Explanation

Question 92 of 120

1

Given that:

(1) Phosphofructokinase-2 (PFK-2), upon phosphorylation, is inactive.
(2) The active PFK-2 converts fructose 6-phosphate to fructose 2,6-bisphosphate.
(3) Fructose 2,6-bisphosphate activates the glycolytic enzyme, phosphofructokinase-1

Which of the statement(s) below is (are) true?

Select one of the following:

  • high glucagon/insulin ratios promote phosphorylation of PFK-2

  • low glucagon/insulin ratios promote phosphorylation of PFK-2

  • - high glucagon/insulin ratios promote phosphorylation of PFK-2
    - low glucagon/insulin ratios promote phosphorylation of PFK-2

  • none of the above are true

Explanation

Question 93 of 120

1

Glucagon phosphorylates pyruvate kinase. This has the effect of _______.

Select one of the following:

  • activating the enzyme and promoting glycolysis

  • deactivating the enzyme and promoting glycolysis

  • -activating the enzyme and promoting glycolysis
    -deactivating the enzyme and promoting glycolysis

  • none of the above

Explanation

Question 94 of 120

1

The _______ of pyruvate can produce lactate.

Select one of the following:

  • oxidation

  • reduction

  • hydrolysis

  • cAMP-dependent phosphorylation

  • cAMP-independent phosphorylation

Explanation

Question 95 of 120

1

Glyceraldehyde 3-phosphate is converted to 1,3-bisphosphoglycerate (1,3-BPG) by the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase. The product of the above reaction can be converted to 3-phosphoglycerate in a reaction catalyzed by phosphoglycerate kinase. In certain cells, however, a significant amount of the product of the first reaction can undergo instead an isomerization reaction, which is catalyzed by bisphosphoglycerate mutase. This isomerization can be induced by _________.

Select one of the following:

  • insulin

  • glucagon

  • glycogen

  • anoxia

Explanation

Question 96 of 120

1

Which of the following statement(s) about the TCA cycle is (are) true?

Select one of the following:

  • the TCA cycle is both anabolic and catabolic (amphibolic)

  • the enzymes of the TCA cycle are located in the mitochondrial matrix

  • the TCA cycle produces carbon dioxide

  • - the TCA cycle is both anabolic and catabolic (amphibolic)
    - the enzymes of the TCA cycle are located in the mitochondrial matrix
    - the TCA cycle produces carbon dioxide

  • none of the above

Explanation

Question 97 of 120

1

A genetic defect in which of the following is most likely to cause lactic acidosis? (NOTE: Please disregard the frequency of the defect and the potential health issues associated with the mutation.)

Select one of the following:

  • pyruvate dehydrogenase complex

  • glucokinase

  • hexokinase

  • pyruvate kinase

  • phosphofructokinase

Explanation

Question 98 of 120

1

Which of the following coenzymes is (are) NOT essential for the activity of the pyruvate dehydrogenase complex?

Select one of the following:

  • ascorbate

  • thiamine

  • riboflavin

  • niacin

  • none of the above are essential for the activity of the pyruvate dehydrogenase complex

Explanation

Question 99 of 120

1

A sickling crisis _________ the ratio of NADH to NAD+, and also ___________ the formation of lactate.

Select one of the following:

  • raises, promotes

  • raises, inhibits

  • lowers, promotes

  • lowers, inhibits

Explanation

Question 100 of 120

1

The oxidation of alcohol _________ the levels of NAD+ relative to NADH in the liver.

Select one of the following:

  • raises

  • lowers

Explanation

Question 101 of 120

1

GLycolysis is active in the _________ of __________ in a healthy human being.

Select one of the following:

  • mitochondria, only anaerobically functioning cells

  • cytosol, only anaerobically functioning cells

  • mitochondria, all cells

  • cytosol, all cells

  • mitochondria and cytosol, only anaerobically functioning

Explanation

Question 102 of 120

1

Pyruvate dehydrogenase complex (PDC) is active in the unphosphorylated form. The protein kinase that specifically phosphorylates PDC is inactivated by ________.

Select one of the following:

  • Pyruvate

  • Acetyl CoA

  • - Pyruvate
    - Acetyl CoA

  • None of the above

Explanation

Question 103 of 120

1

I-cell disease is caused by a genetic defect in an enzyme that normally ___________.

Select one of the following:

  • transfers a mannose onto a growing glycoprotein

  • is involved in the production of a specific receptor in the cis-Golgi

  • hydrolyzes a specific sugar residue located on the terminus of the glycoprotein

  • adds a phosphate to specific mannose residues in the glycoprotein

  • is involved in the production of a specific receptor inside the lysosome

Explanation

Question 104 of 120

1

Glycoproteins that are destined for ____________ are generally synthesized on free cytosolic ribosomes.

Select one of the following:

  • cellular membranes

  • export from the cell

  • lysosomes

  • - cellular membranes
    - export from the cell
    - lysosomes

  • none of the above

Explanation

Question 105 of 120

1

Which of the following statement(s) about the synthesis of dolichol-linked oligosaccharides is (are) true?

Select one of the following:

  • a branched oligosaccharide is synthesized on dolichol pyrophosphate

  • the oligosaccharide synthesized on dolichol pyrophosphate is transferred to asparagine inside the lumen of the lysosome

  • the oligosaccharide synthesized on dolichol pyrophosphate is transferred to a serine or threonine inside the lumen of the endoplasmic reticulum

  • - a branched oligosaccharide is synthesized on dolichol pyrophosphate
    - the oligosaccharide synthesized on dolichol pyrophosphate is transferred to asparagine inside the lumen of the lysosome
    - the oligosaccharide synthesized on dolichol pyrophosphate is transferred to a serine or threonine inside the lumen of the endoplasmic reticulum

  • none of the above are true

Explanation

Question 106 of 120

1

I-cell disease is characterized by ________.

Select one of the following:

  • very high concentrations in the plasma and the urine of intact substrate molecules that normally should have been hydrolyzed in the lysosomes

  • the accumulation in the lysosomes of intact substrate molecules that normally should have been hydrolyzed in the lysosomes

  • the accumulation in the plasma and urine of intact lysosomes

  • non-genetic defects of specific lysosomal enzymes

  • none of the above

Explanation

Question 107 of 120

1

Which sugar is NOT a reducing sugar

Select one of the following:

  • glucose

  • maltose

  • ribose

  • lactose

  • none of the above

Explanation

Question 108 of 120

1

The active site of an enzyme ________.

Select one of the following:

  • is formed only after the addition of a specific substrate

  • is directly involved in binding of allosteric inhibitors

  • resides in a few adjacent amino acid residues in the primary sequence of the polypeptide chain

  • binds competitive inhibitors

Explanation

Question 109 of 120

1

Which of the following describes a characteristic feature of an enzyme obeying Michaelis-Menten kinetics?

Select one of the following:

  • the enzyme velocity is at 1/2 the maximal rate when 100% of the enzyme molecules contain bound substrate

  • the enzyme velocity is at 1/2 the maximal rate when 50% of the enzyme molecules contain bound substrate

  • the enzyme velocity is at its maximal rate when 50% of the enzyme molecules contain bound substrate

  • the enzyme velocity is at its maximal rate when all of the substrate molecules in solution are bound by the enzyme

  • the velocity of the reaction is independent of the concentration of the enzyme

Explanation

Question 110 of 120

1

A homotropic effector of an allosteric enzyme is:

Select one of the following:

  • an activator which is not the substrate

  • the substrate of the enzyme

  • a competitive inhibitor of the enzyme

  • a noncompetitive inhibitor of the enzyme

Explanation

Question 111 of 120

1

Glycogen phosphorylase can be activated by phosphorylation of the enzyme. This is called:

Select one of the following:

  • allosteric activation

  • homotropic activation

  • covalent modification

  • irreversible inhibition

Explanation

Question 112 of 120

1

Which of the following has/have been used for the diagnosis of myocardial infarction?

Select one of the following:

  • lactic dehydrogenase

  • creatine phosphokinase

  • troponin T

  • - lactic dehydrogenase
    - creatine phosphokinase
    - troponin T

  • none of the above

Explanation

Question 113 of 120

1

A urine sample gave a positive reducing sugar test but was negative when measured with glucose oxidase test which is specific for glucose. Treatment of the sample with acid which cleaves glycosidic bonds did not increase the amount of reducing sugar measured. Which of the following compounds is most likely to be present in the urine sample?

Select one of the following:

  • glucose

  • galactose

  • sorbitol (glucitol)

  • maltose

  • lactose

Explanation

Question 114 of 120

1

In glycoproteins, the oligosaccharide moieties (chains) can be covalently linked to one of the following amino acyl residues of a protein EXCEPT:

Select one of the following:

  • asparagine

  • threonine

  • serine

  • alanine

Explanation

Question 115 of 120

1

D-Glucose is an epimer of:

Select one of the following:

  • D-glucuronic acid

  • D-gluconic acid

  • D-mannose

  • D-fructose

  • L-arabinose

Explanation

Question 116 of 120

1

In glycogen, the glucosyl moieties are joined by ______ linkages except at the branch points, where they are joined by ________ linkage.

Select one of the following:

  • alpha(1,4); alpha(1,2)

  • alpha(1,4); alpha(1,6)

  • beta(1,4); beta(1,6)

  • beta(1,4); alpha(2,6)

  • alpha(1,6); alpha(1,4)

Explanation

Question 117 of 120

1

Which one of the following is NOT a coenzyme?

Select one of the following:

  • pyridoxal phosphate

  • thiamin pyrophosphate

  • ergocalciferol

  • tetrahydrofolic acid

Explanation

Question 118 of 120

1

Vitamin K is required for which of the following?

Select one of the following:

  • intestinal absorption of bacteria

  • hydroxylation of glutamic acid in collagen

  • post-translational modification of Blood Clotting Factor X

  • carboxylation of aspartic acid residues

  • none of the above

Explanation

Question 119 of 120

1

The cofactor required by hexokinase is:

Select one of the following:

  • Zn+2

  • Mg+2

  • Cu+2

  • K+

Explanation

Question 120 of 120

1

Which of the following statements is true?

Select one of the following:

  • coenzyme + holoenzyme = vitamin

  • coenzyme + holoenzyme = cofactor

  • vitamin + coenzyme = holoenzyme

  • coenzyme + apoenzyme = holoenzyme

Explanation

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