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Biochemistry > Discussion chapter 8 > Flashcards

Discussion chapter 8 Flashcards

1
Q

Glycogen synthase is activated by _________ and inactivated by _________, whereas glycogen phosphorylase is activated by _________ and inactivated by _________.

dephosphorylation, phosphorylation; phosphorylation; dephosphorylation

phosphorylation, dephosphorylation; phosphorylation; dephosphorylation

phosphorylation, dephosphorylation; dephosphorylation; phosphorylation

dephosphorylation, dephosphorylation; phosphorylation; phosphorylation

A

dephosphorylation, phosphorylation; phosphorylation; dephosphorylation

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2
Q

Glycogen synthase and glycogen phosphorylase _________.

A) can be activated simultaneously under all circumstances

B) can be activated simultaneously under special circumstances

C) can be activated simultaneously under no circumstances

D) are modified by the same enzymes

E) both C and D

A

E) both C and D

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3
Q

Which molecule is used for direct incorporation of glucose into glycogen during glycogenesis?

sucrose

UDP-glucose

fructose-1,6-bisphosphate

glucose-1-phosphate

glucose-3-phosphate

A

UDP-glucose

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4
Q

If an individual goes most of day without eating, the glycogen synthase in their cells is likely to be _________________ , and thus in the ___________________ state, while glycogen phosphorylase is likely to be ____________________, and therefore in the __________________ state. In this state, signal cascades activated by __________________ are regulating the synthesis or breakdown of glycogen.

A

Phosphorylated, inactive, B, Phosphorylated, A, Glucagon.

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5
Q

Where are the two major sites for glycogen storage in humans?

Liver and kidney

Liver and brain

Liver and muscle

Muscle and kidney

Adipose tissue and kidney

A

Liver and muscle

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6
Q

Which of the following statements is TRUE regarding glycogen synthase?

It is activated by protein kinases.

It is activated by Ca2+ ions.

It catalyzes formation of glycosidic bonds.

It uses glucose-1-phosphate as a substrate.

A

It catalyzes formation of glycosidic bonds.

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7
Q

Which of the following statements about glycogen is FALSE?

It consists of glucose residues linked by α(1-6)- and α(1-4)-glycosidic bonds.

It allows for the storage of many glucose molecules.

UDP-glucose is an “activated” compound that can donate a glucose molecule to a growing glycogen chain.

Glycogen signals the fasting state and is released into the bloodstream when blood sugar levels are low.

A

Glycogen signals the fasting state and is released into the bloodstream when blood sugar levels are low.

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8
Q

Which of the following is FALSE regarding glycogen?

Branching enables more rapid breakdown of glycogen.

Glucose is stored as a polymer to reduce its chemical reactivity.

The main chain of the glycogen polymer predominately contains glucose residues linked via 1-6 glycosidic bonds.

The first step in glycogen synthesis is catalyzed by hexokinase.

A

The main chain of the glycogen polymer predominately contains glucose residues linked via 1-6 glycosidic bonds.

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9
Q

The pentose phosphate pathway is divided into two phases, oxidative and nonoxidative. What are the respective functions of these two phases?

to generate reducing equivalents for the other pathways in the cell; to generate ribose from other monosaccharides

to generate ribose from other monosaccharides; to generate reducing equivalents for other pathways in the cell

to generate energy for nucleotide biosynthesis; to provide monosaccharides for nucleotide biosynthesis

to provide monosaccharides for nucleotide biosynthesis; to generate energy for nucleotide biosynthesis

to provide monosaccharides for amino acid biosynthesis; to generate reducing equivalents for other pathways in the cell

A

to generate reducing equivalents for the other pathways in the cell; to generate ribose from other monosaccharides

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10
Q

Which substrate regulates flux through the pentose phosphate pathway?

NAD+

Glucose-6-phosphate

Ribose 5-phosphate

A

NAD+

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11
Q

NADPH used in lipid biosynthesis is produced by the ________________ pathway.

A

Pentose Phosphate

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12
Q

The oxidative portion of the pentose phosphate pathway generates two molecules of _______________ for each molecule of G6P.

A

NADPH

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13
Q

Ru5P is converted to Xu5P by ribulose-5-phosphate ___________________

A

Epimerase

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14
Q

Where in a given cell would you be most likely to find these different types of glycoconjugates?

glycoprotein
glycolipid
proteoglycan
peptidoglycan

A

Extracellular matrix
Cell membrane
Extracellular matrix
Cell wall

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15
Q

Match the protein with its component:

liver and muscle
elastin
glucuronic acid and N-acetylglucosamine
peptidoglycans
left-handed helix

A

Glycogen storage
Proline and Glycine
Hyaluronic acid
Bacterial cell wall
Collagen

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16
Q

The main component of a bacterial cell wall is a __________________

A

Peptidoglycan

17
Q

N-linked oligosaccharides can be covalently linked to proteins at which amino acid?

Gly
Ser
Glu
Tyr
Asn

A

Asn

18
Q

Vitamin C (ascorbic acid) is required for the hydroxylation of _________ during collagen synthesis.

A) serine

B) proline

C) lysine

D) all of the above

E) both A and B

A

Proline

19
Q

Which of the following correctly relates the order of intermediates during the synthesis of glycogen?

glucose→glucose-1-phosphate→glucose-6-phosphate→UDP-glucose→glycogen

glucose→glucose-6-phosphate→glucose-1-phosphate→UDP-glucose→glycogen

glucose→glucose-6-phosphate→UDP-glucose→glucose-1-phosphate→glycogen

glucose→UDP-glucose→glucose-1-phosphate→glucose-6-phosphate→glycogen

glucose→UDP-glucose→glucose-6-phosphate→glucose-1-phosphate→glycogen

A

glucose→glucose-6-phosphate→glucose-1-phosphate→UDP-glucose→glycogen

20
Q

Which enzyme below is not required for the synthesis of branched glycogen?

glycogen phosphorylase

glycogen synthase

branching enzyme

phosphoglucomutase

All are required for synthesis of glycogen.

A

glycogen phosphorylase

21
Q

The main enzyme of glycogen catabolism is _____, which catalyzes a _____ reaction.

glycogen hydrolase; hydrolysis

glycogen phosphorylase; phosphorolysis

glycogen mutase; mutarotation

debranching enzyme; hydrolysis

glycogen transferase; glucose residue transfer

A

glycogen phosphorylase; phosphorolysis

22
Q

Which of the following statements about glycogen is true?

I. Glycogen is a polymer of glucose in α(1→6) linkages with α(1→4) linked branches every 8–14 residues.
II. UDP–glucose is produced from glycogen by the action of the enzyme phosphorylase.
III. In glycogen breakdown, glucose residues are sequentially removed from the nonreducing ends.
IV. The breakdown of glycogen in skeletal muscle ultimately supplies glucose-6-phosphate, which can enter glycolysis to generate ATP.

I, II, III, IV

I, II

II, III, IV

III, IV

III only

A

III, IV

23
Q

The glycogen debranching enzyme is required for _____.

A) the transfer of 3-glucose units from one branch to another

B) the transfer of phosphate from one position to another

C) cleaving α(1→6) sugar linkages

D) A and C

E) A, B, and C

A

D) A and C

24
Q

A deficiency in muscle glycogen phosphorylase would result in _____.

A) normal muscle glycogen structure

B) abnormal muscle glycogen structure

C) elevated muscle glycogen levels

D) A and C

E) B and C

A

D) A and C

25
Q

Which of the following requires large amounts of ribose-5-phosphate?

DNA synthesis

amino acid synthesis

lipid synthesis

glycogen synthesis

cholesterol synthesis

A

DNA synthesis

26
Q

For each molecule of glucose-6-phosphate that enters the oxidative phase of the pentose phosphate pathway, _____ NADPH and _____ CO2 are produced.

1; 0

1; 1

2; 1

2; 2

3; 2

A

2; 1

27
Q

Which of the following enzymes catalyzes an oxidative decarboxylation reaction?

glucose-6-phosphate dehydrogenase

glyceraldehyde-3-phosphate dehydrogenase

glycogen dehydrogenase

6-phosphogluconate dehydrogenase

none of the above

A

6-phosphogluconate dehydrogenase

28
Q

In the conversion of ribulose-5-phosphate to glycolytic intermediates, which of the following enzymes is used?

phosphoglucomutase

transketolase

phosphoglycerate mutase

phosphofructoisomerase

none of the above

A

transketolase

29
Q

In the ABO blood type system, how many monosaccharides are found in each of the oligosaccharides for the various blood types?

A: 3, B: 4, O: 3

A: 4, B: 5, O: 4

A: 6, B: 5, O: 5

A: 6, B: 6, O: 5

A: 5, B: 5, O: 4

A

A: 6, B: 6, O: 5

30
Q

In a _____, the carbohydrate is responsible for most of the mass; in a _____, the protein is responsible for most of the mass.

glycoprotein; proteoglycan

proteoglycan; glycoprotein

N-linked glycoprotein; O-linked glycoprotein

O-linked glycoprotein; N-linked glycoprotein

N-linked proteoglycan; O-linked glycoprotein proteoglycan

A

proteoglycan; glycoprotein

31
Q

Bacterial cell walls are made of _____.

pectin

chondroitin sulfate

peptidoglycans

keratin sulfate

heparin

A

peptidoglycans

32
Q

Is glycogen a reducing sugar? Explain.

Yes, glycogen is made from glucose.

No, glycogen lacks the free aldehyde necessary to reduce copper.

Yes, glycogen has multiple free aldehydes which can reduce copper.

No, glycogen is already reduced.

A

No, glycogen lacks the free aldehyde necessary to reduce copper.

33
Q

Why does the pentose phosphate pathway take place in the cytosol?

The reagent NAD+ is only found in the cytosol.

The pentose phosphate pathway takes place in the Endoplasmic Reticulum.

If it took place in mitochondria it would compete with other metabolic pathways found there.

Substrates for other pathways in which carbohydrates are metabolized are found in the cytosol.

A

Substrates for other pathways in which carbohydrates are metabolized are found in the cytosol.

34
Q

Which of the following enzymes directly converts phosphorylase b into the more active form, phosphorylase a?

cAMP-dependent protein kinase
phosphorylase kinase
protein kinase A
adenylate cyclase
phosphoprotein phosphatase-1

A

phosphorylase kinase

35
Q

In the event that NADPH is needed but ribose is not, which of the following is an end product of the pentose phosphate pathway?

ribulose-5-phosphate

dihydroxyacetone phosphate

fructose-1,6-bisphosphate

1,3-bisphosphoglycerate

glyceraldehyde-3-phosphate

A

glyceraldehyde-3-phosphate

36
Q

The helical structure of collagen contains _____.

three right-handed helices wound around each other in a right-handed triple helix

three right-handed helices wound around each other in a left-handed triple helix

three left-handed helices wound around each other in a left-handed triple helix

three left-handed helices wound around each other in a right-handed triple helix

none of the above

A

three left-handed helices wound around each other in a right-handed triple helix

Biochemistry (32 decks)

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