Deck 16: Carbohydrate Metabolism II: Special Pathways and Glycoconjugates

Question 1

The carbohydrate used in the synthesis of nucleic acids in animals is produced in

A) the urea cycle.
B) glycolysis.
C) the citric acid cycle.
D) electron transport.
E) the hexose monophosphate pathway.

Answer 1

the hexose monophosphate pathway.

Question 2

The bond linking chondroitin sulfate to protein in bovine cartilage involves a residue of

A) galactose.
B) N-acetylglucosamine.
C) glucuronic acid.
D) xylose.
E) mannose.

Answer 2

xylose.

Question 3

Phosphoadenosine phosphosulfate (PAPS) participates in the

A) biosynthesis of heparan.
B) synthesis of glutathione.
C) synthesis of cysteine from methionine.
D) conversion of cysteine to taurine.
E) conversion to sulfite to sulfate.

Answer 3

biosynthesis of heparan.

Question 4

All of the following are glycosaminoglycans EXCEPT

A) hyaluronate.
B) heparin.
C) chondroitin sulfate.
D) keratan sulfate.
E) glucuronate.

Question 5

What makes hyaluronic acid different from the other 5 classes of proteoglycans?

A) It is limited to animal tissue
B) It is not a lubricant
C) It is not acetylated
D) It is not charged
E) It is not sulfated

Question 6

Which of the following generates NADPH?

A) Glycolysis
B) hexose monophosphate shunt
C) Krebs cycle
D) Gluconeogenesis
E) Glycogenolysis

Question 7

Erythrose 4-phosphate + fructose 6-phosphate <--> sedoheptulose 7-phosphate + glyceraldehyde 3-phosphate This reaction is catalyzed by

A) transaminase.
B) transhydrogenase.
C) transketolase.
D) transamidinase.
E) transaldolase.

Question 8

All of the following are accomplished by the hexose monophosphate shunt EXCEPT

A) hexose may be converted to pentose.
B) glucose-6-phosphate may be synthesized from pentose phosphates.
C) a major source of energy is supplied to the body via oxidation of NADPH by the electron transport chain.
D) pentoses may be converted into glycolytic intermediates and then to pyruvate.

Question 9

The principal regulatory factor governing the rate of the pentose phosphate pathway is the level of

A) ATP
B) ADP
C) AMP
D) NAD⁺
E) NADP⁺

Question 10

The asparagine-linked oligosaccharides of mammalian glycoproteins, when processed to the mature form, may contain residues of each of the following EXCEPT

A) glucose.
B) fucose.
C) N-acetyl glucosamine.
D) mannose.
E) sialic acid.

Question 11

All of the following occur in the hexose monophosphate pathway for glucose metabolism EXCEPT

A) reduction of NAD.
B) formation of C-7 sugar phosphates.
C) formation of C-5 sugar phosphate precursor of nucleotides.
D) release of C-1 of glucose as carbon dioxide.
E) reduction of NADP.

Question 12

What is the minimum number of carbohydrate residues that defines a protein as a glycoprotein?

A) 1
B) 5
C) 50
D) 100
E) 500

Question 13

HMP shunt occurs in

A) nucleus.
B) nucleus and microsomes.
C) cytosol.
D) mitochondria.

Question 14

Proteoglycan monomers contain

A) glycosaminoglycans.
B) derivatives of mannosamine.
C) either mannuronic acid or iduronic acid.
D) repeating trisaccharide units.

Question 15

What percentage of carbohydrate determines that a molecule is a proteoglycan and not a glycoprotein?

A) 5
B) 25
C) 55
D) 75
E) 95

Question 16

The hexose monophosphate shunt pathway is utilized for all of the following EXCEPT

A) formation of ATP.
B) generation of NADPH.
C) ribose 5-phosphate synthesis.
D) ribose 5-phosphate degradation.
E) synthesis of pentoses.

Question 17

Which statement about proteoglycans is FALSE?

A) They contain long chains of repeating disaccharides.
B) They are polyanions.
C) They contain roughly equal amounts by weight of protein and carbohydrate.
D) Carbohydrate residues frequently are esterified with sulfate.
E) They generally form viscous solutions in water.

Question 18

Which mucopolysaccharide contains alpha 1->4 glycosidic bonds?

A) chondroitin sulfate A
B) chondroitin sulfate B
C) heparin
D) hyaluronic acid
E) dermatan sulfate

Question 19

Hyaluronic acid consists of repeating units of

A) glucose and fructose.
B) glucuronic acid and N-acetylglucosamine.
C) galactose and N-acetylgalactosamine.
D) glucuronic acid and N-acetylgalactosamine.
E) glucuronic acid and N-acetylgalactosamine-4-sulfate.

Question 20

A nine carbon acid found in a terminal position in the oligosaccharide portion of many glycoproteins is

A) hyaluronic acid.
B) sialic acid.
C) iduronic acid.
D) glucuronic acid.
E) gluconic acid.

Question 21

In glucose 6-phosphate dehydrogenase deficiency, the associated hemolytic anemia is ultimately due to what changes from normal in red cells?

A) decreased formation of ATP by mitochondria.
B) decreased ability to carry out glycolysis.
C) increased leakage of potassium into the cells.
D) an intrinsic defect in membrane structure.
E) decreased concentrations of NADPH.

Question 22

All of the following molecules are formed in the pentose phosphate pathway EXCEPT

A) carbon dioxide
B) pentose 5-phosphate
C) NADPH
D) NADH
E) glyceraldehyde 3-phosphate

Question 23

All of the following are reactants or products of the pentose phosphate pathway for glucose oxidation EXCEPT

A) certain triose phosphates.
B) FADH₂.
C) glucose 6-phosphate.
D) CO₂.
E) a certain 7 carbon sugar.

Question 24

All of the following are intermediates in the conversion of glucose to ribose EXCEPT

A) 6-phosphogluconate.
B) D-ribulose 5-phosphate.
C) ribose 5-phosphate.
D) glucose 1-phosphate.
E) glucose 6-phosphate.

Question 25

Hyaluronic acid is characterized by

A) several polysaccharide chains attached to protein.
B) repeating trisaccharide units.
C) sulfated N-acetylglucosamine residues.
D) beta-glycosidic bonds.

Question 26

The immediate products of oxidation of one mole of glucose 6-phosphate through the oxidative portion of the pentose phosphate pathway are

A) one mole of ribulose 5-phosphate, one mole of carbon dioxide and reduction of two moles of NAD.
B) one mole of ribulose 5-phosphate, one mole of carbon dioxide and oxidation of two moles of NADPH.
C) one mole of xylulose 5-phosphate, one mole of carbon dioxide and reduction of two moles of NADPH.
D) one mole of ribose 5-phosphate, one mole of carbon dioxide and reduction of two moles of NADPH.
E) one mole of fructose 6-phosphate and reduction of two moles of NADP.

Question 27

The non-oxidative portion of the hexose monophosphate shunt

A) forms CO2 as glucose 6-phosphate is converted to pentose phosphates.
B) requires ATP.
C) converts lactate to pyruvate.
D) does not function in mature erythrocytes.
E) can lead to synthesis of hexose phosphates from pentose phosphates.

Question 28

Comparing keratan sulfate dermatan sulfate, chondroitin sulfate and hyaluronate, all of the following statements are true EXCEPT which ones?

A) they all contain a uronic acid.
B) all have 1 --> 4 linkages in them
C) all contain N-acetylgalactosamine
D) all contain acetyl groups
E) all contain beta-glycosidic bonds

Question 29

The first intermediate formed from glucose in the pentose phosphate pathway is

A) 6-phosphogluconolactone.
B) 6-phosphogluconate.
C) fructose 6-phosphate.
D) ribulose 5-phosphate.
E) glucose 1-phosphate.

Question 30

The hexose monophosphate shunt is least active in

A) liver
B) adipose tissue
C) red blood cells
D) skeletal muscle
E) gonads and adrenal tissue

Question 31

The enzyme transketolase is a component of

A) the TCA cycle.
B) the HMP shunt.
C) fatty acid synthase.
D) the pyruvate dehydrogenase complex.
E) none of the above

Question 32

Which of the following is NOT found as an intermediate or product of the pentose phosphate pathway?

A) NADPH
B) ribulose 5-phosphate
C) xylulose 5-phosphate
D) ribose 5-phosphate
E) NADH

Question 33

The products of the pentose phosphate pathway include

A) NAD+ and pyruvate.
B) NADH and pentose phosphate.
C) NADPH and carbon dioxide.
D) ATP, pentose phosphate and carbon dioxide.

Question 34

Proteoglycan monomers contain

A) glycosaminoglycans.
B) derivatives of mannosamine.
C) either mannuronic acid or iduronic acid.
D) repeating trisaccharide units.

Question 35

Which enzyme catalyzes a decarboxylation?

A) 6-phosphogluconate dehydrogenase
B) glucose 6-phosphate dehydrogenase
C) pyruvate kinase
D) beta-hydroxybutyrate dehydrogenase
E) citrate lyase

Question 36

Thiamine pyrophosphate participates in the reaction catalyzed by

A) transketolase.
B) transaldolase.
C) pyruvate carboxylase.
D) isocitrate dehydrogenase.
E) aspartate aminotransferase (GOT).

Question 37

What is the major difference in the synthesis of N- and O-linked carbohydrate residues on glycoproteins?

A) N-linked has branches
B) N-linked has mannose
C) O-linked is assembled on a dolichol intermediate
D) O-linked is assembled on the protein
E) Synthesis of O-linked requires energy

Question 38

The nitrogen donor for amino sugars is

A) glutamate.
B) glucosamine.
C) ammonia.
D) glutamine.
E) none of the above

Question 39

Which group of compounds are all intermediates in the hexose monophosphate shunt?

A) sedoheptulose 7-phosphate, glucose 6-phosphate, xylulose 5-phosphate
B) erythrose 4-phosphate, glucose 1-phosphate, glycerol 3-phosphate
C) fructose 6-phosphate, fructose 1-phosphate, fructose 1,6-phosphate
D) glucose 1-phosphate, erythrose 4-phosphate, carbon dioxide
E) ribulose 5-phosphate, ribose 1-phosphate, glucose 6-phosphate

Question 40

The enzyme transaldolase is a component of

A) the TCA cycle
B) the hexose monophosphate shunt
C) fatty acid synthase
D) the pyruvate dehydrogenase complex
E) none of the above

Question 41

All of the following statements about the phosphogluconate (pentose phosphate) pathway are correct EXCEPT which one?

A) A carbohydrate containing 7 carbon atoms can be produced by this pathway.
B) containing 5 carbon atoms are absent from this pathway.
C) A major product of the pathway is NADPH.
D) The pathway is important in red blood cells because a product of the pathway is required for maintaining the proper oxidation-reduction state.
E) A key enzyme in the pathway is glucose 6-phosphate dehydrogenase.

Question 42

The oligosaccharide moiety of glycoproteins is synthesized and processed in or on

A) cytosol.
B) lysosomes.
C) endoplasmic reticulum.
D) nucleus.
E) mitochondria.

Question 43

Proteoglycans

A) contain repeating trisaccharide units.
B) contain N-acetyl mannosamine.
C) usually contain either glucuronic acid or iduronic acid.
D) are composed of glycosaminoglycans covalently attached to a protein core through a N-glycosidic linkage to asparagine

Question 44

The inner core of N-linked glycoproteins contains which of the following sugar residues?

A) galactose and N-acetyl galactosamine
B) mannose and N-acetyl glucosamine
C) mannose and galactose
D) fucose and N-acetyl glucosamine
E) mannose and N-acetyl neuraminic acid

Question 45

All of the following are products or intermediates of the hexose monophosphate pathway EXCEPT

A) carbon dioxide.
B) 6-phosphogluconate.
C) ribulose 5-phosphate.
D) a 4-carbon sugar phosphate.
E) NADH.

Question 46

The active glucosyl donor in biosynthesis

A) glucose?l?phosphate
B) 3'-glucosyl?ATP
C) UDP?glucose
D) UDP?maltose
E) UDP?glucose?6?diphosphate

Question 47

The oxidative branch of the pentose phosphate pathway predominates over the nonoxidative branch when

A) more ribose 5-phosphate than NADPH is required.
B) the needs for NADPH and ribose 5-phosphate are balanced.
C) more NADPH than ribose 5-phosphate is required.
D) more sedoheptulose 7-phosphate than NADPH is required.

Question 48

The core sugars of N-linked oligosaccharides are preassembled as a derivative of ______ prior to their transfer to a newly synthesized polypeptide.

A) adenosine diphosphate
B) coenzyme A
C) dolichol phosphate
D) thiamine pyrophosphate
E) phosphoenolpyruvate

Question 49

All of the following substances are intermediates in the formation of glucuronic acid from glucose EXCEPT

A) UDP-glucose.
B) UDP-galactose.
C) UDP-glucuronic acid.
D) glucose 6-phosphate.
E) glucose 1-phosphate.

Question 50

All of the following are products or intermediates of the hexose monophosphate shunt (pentose phosphate pathway) EXCEPT

A) glucuronic acid 1-phosphate.
B) carbon dioxide.
C) glyceraldehyde 3-phosphate.
D) NADPH.
E) ribose 5-phosphate.

Question 51

The precursors for the biosynthesis of N-acetylneuraminic acid include which two of the following? 1. phosphoenolpyruvate 2. N-acetylmannosamine 3. CMP 4. N-acetylgalactosamine 5. glucuronic acid

A) 1 and 2
B) 2 and 3
C) 3 and 4
D) 4 and 5
E) 1 and 5

Question 52

In nature most mucopolysaccharides or glycosaminoglycans are found covalently linked to protein cores. Which is not?

A) hyaluronic acid
B) chondroitin sulfate
C) heparin (mast cell)
D) dermatan sulfate
E) heparan sulfate

Question 53

All of the following are directly associated with the pentose phosphate pathway EXCEPT

A) fructose 6-phosphate.
B) production of pentose phosphates.
C) synthesis of NADPH.
D) glyceraldehyde 3-phosphate.
E) glycerol 3-phosphate.

Question 54

Which of the following heteropolysaccharides is frequently used clinically as an anticoagulant?

A) hyaluronic acid
B) keratin sulfate
C) heparin
D) dermatin sulfate
E) chondroitin sulfate

Question 55

Sulfation of heparin occurs by means of sulfate transfer from by the action of a sulfotransferase.

A) heparin sulfate
B) 3'-phosphoadenosine-5'-phosphosulfate
C) 3'-phosphoadenosine-5'-phosphate
D) cysteine
E) both A and D

Question 56

In the reaction below, catalyzed by transketolase, what is compound Z? Z + ribose-5-P <--> glyceraldehyde-3-P + sedoheptulose-7-P

A) erythrose 4-phosphate
B) fructose 6-phsophate
C) 6-phosphogluconate
D) ribulose
E) xylulose 5-phosphate

Question 57

Proteoglycan aggregates contain all of the following EXCEPT which one?

A) Protein chain
B) Keratin sulfate
C) Dermatan sulfate
D) chondroitin sulfate
E) Hyaluronic acid

Question 58

All of the following glycosaminoglycans contains sulfate attached to a carbohydrate molecule except one. What is the exception?

A) Hyaluronic acid
B) chondroitin-4-sulfate
C) Dermatan sulfate
D) Keratan
E) Heparin

Question 59

Which of the following best indicates the products of the hexose monophosphate hunt?

A) NAD and pyruvate
B) the oxidized form of NADPH
C) carbon dioxide and NADPH
D) NADH and pentoses
E) ATP, pentoses and carbon dioxide

Question 60

The nonoxidative branch of the pentose phosphate pathway predominates over the oxidative branch when

A) more ribose 5-phosphate than NADPH is required.
B) the needs for NADPH and ribose 5-phosphate are balanced.
C) more NADPH than ribose 5-phosphate is required.
D) more NADPH than sedoheptulose 7-phosphate is required.

Question 61

Which of the glycosaminoglycans found in proteoglycan aggregates is devoid of uronic acid units?

A) dermatan sulfate
B) keratan sulfate
C) heparan sulfate
D) chondroitin-4-sulfate
E) chondroitin-6-sulfate

Question 62

Which of the following participates in N-acetyl neuraminic acid transfer reactions in man?

A) UDP-beta-D-N-acetyl neuraminic acid
B) GDP-alpha-D-N-acetyl neuraminic acid
C) CMP-N-acetyl neuraminic acid
D) UDP-alpha-D-N-acetyl neuraminic acid
E) GDP-beta-D-N-acetyl neuraminic acid

Question 63

Which class of proteoglycans is most abundant in the body?

A) chondroitin sulfate
B) Dermatan sulfate
C) Heparin
D) Heparan sulfate
E) Keratan sulfate

Question 64

In liver, the hexose monophosphate shunt is the principal source of

A) carbon dioxide.
B) glucose 6-phosphate.
C) the reduction of NAD.
D) fructose 6-phosphate.
E) ribose 5-phosphate.

Question 65

The activated form of glucose involved in the biosynthesis of glycoproteins, galactose and glucuronic acid is a derivative of

A) CoA.
B) ADP.
C) pantothenic acid.
D) UDP.
E) ascorbic acid.

Question 66

Glucose 6-phosphate dehydrogenase catalyzes the first step in which of the following pathways?

A) glycolysis
B) pentose phosphate pathway
C) gluconeogenesis
D) tricarboxylic acid cycle
E) glycogen synthesis

Question 67

All of the following occur in the pentose phosphate pathway EXCEPT

A) Reduction of NADP.
B) Formation of C-7 monosaccharide phosphates.
C) Formation of C-5 monosaccharide phosphate precursors of nucleotides.
D) Release of C-6 of glucose as carbon dioxide.
E) Formation of 6-phosphogluconolactone.

Question 68

Carbon number 1 of glucose in the hexose monophosphate shunt is converted to

A) ribose.
B) deoxyribose.
C) carbon dioxide.
D) fatty acid.

Question 69

Which statement is FALSE?

A) Hyaluronic acid is a glycosaminoglycan (GAG) but not a proteoglycan.
B) In proteoglycans, the GAGs are linked to serine residues in the core protein.
C) The major sugar components of proteoglycans are pentoses, such as xylose, and N-acetylamino sugars.
D) proteoglycans typically carry many negative charges.
E) Hurler's disease results from deficient activity of an enzyme normally involved in the degradation of GAGs.

Question 70

What is a major function of the hexose monophosphate shunt?

A) produces pentoses
B) produces ADP
C) produces NADH
D) pathway for glucuronic acid synthesis
E) None of the above is correct.

Question 71

Which of the following is the first enzyme unique to the pentose phosphate pathway?

A) lactonase
B) 6-phosphogluconate dehydrogenase
C) transaldolase
D) glucose 6-phosphate dehydrogenase
E) phosphoglucoisomerase

Question 72

Which of the following statements about N-glycosylation of proteins is FALSE

A) The oligosaccharide contains both mannose (Man) and N-acetyl- glucosamine (GlcNAc) residues.
B) The oligosaccharide is built up on the protein beginning with attachments of GlcNAc to asparagine and subsequent additions of either GlcNAc or Man residues from the corresponding UDP sugars.
C) The transfer is made from a lipid intermediate called dolichol.
D) transfer occurs within the endoplasmic reticulum.
E) The biosynthesis of dolichol-PP-oligosaccharide is inhibited by tunicamycin.

Question 73

Which of the following is not a function of the pentose phosphate pathway?

A) provide NAD⁺ for the oxidation of fatty acids
B) provide NADPH for the synthesis of fatty acids and cholesterol
C) provide ribose?5?phosphate for the synthesis of nucleotides
D) provide NADPH for ribonucleotide reductase for the synthesis of deoxy ribonucleotides
E) All of the above are functions of the pentose phosphate pathway.

Question 74

The products of the pentose phosphate pathway include

A) NAD⁺ and pyruvate.
B) NADH and pentose phosphate.
C) NADPH and carbon dioxide.
D) ATP, pentose phosphate and carbon dioxide.

Question 75

The repeating disaccharide units of glycosaminoglycans (mucopolysaccharides) are composed of a hexosamine residue and a uronic acid residue. Which is the correct disaccharide unit for chondroitin-6-sulfate, the major component of cartilage proteoglycans?

A) N-acetyl-glucosamine-6-sulfate - glucuronic acid
B) N-acetyl-galactosamine-6-sulfate - glucuronic acid
C) N-acetyl-galactosamine-6-sulfate - iduronic acid
D) N-acetyl-glucosamine-6-sulfate - galacturonic acid
E) N-acetyl-mannosamine-6-sulfate - glucuronic acid