Chapter 7 + Quiz Questions Flashcards

1
Q

What are 7 physiological roles of carbohydrates?

A

Sources of Energy, Energy Storage, Structural Roles, Cellular interaction, Cellular Identification, Information Transfer (DNA and RNA), Signaling

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2
Q

Carbohydrates have empirical formulas of _____ where n ≥ ?

A

(CH2O)n, 3 (usually 3-6)

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3
Q

What are the two major classes of carbohydrates, and which groups do they contain?

A
  1. Aldoses - aldehyde groups
  2. Ketoses - ketone groups
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4
Q

What is the structure of Dihydroxyacetone?

A

O double bonded to C, then 2 CH2OH single bonded at 45 degrees from the C

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5
Q

What is the structure of D-Glyceraldehyde?

A

Starting with a central C. Directly below single bonded is a CH2OH. To the left of central C, is a single bonded H. To the right of the central C is a single bonded OH. Above the central C is a single bonded C, going off the top C is a single bonded H 45 degrees to the right, and a double bonded O 45 degrees to the left

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6
Q

Most monosaccharides have ____ asymmetric carbons

A

multiple

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7
Q

The designation of a sugar as either D or L is based on ..?

A

The configuration of the chiral carbon most distant from the carbonyl oxygen

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8
Q

The designation of D or L is relative to..?

A

The reference molecule D-glyceraldehyde

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9
Q

Molecules with n chiral centers will have ___ stereoisomers

A

2^n. e.g. 4 chiral centers -> 16 stereoisomers

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10
Q

What are the 6 common sugars?

A
  1. D-Ribose, 2. D-Deoxyribose, 3. D-Glucose, 4. D-Mannose, 5. D-Galactose, 6. D-Fructose
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11
Q

In solution, longer carbohydrates (5 carbons and up) tend to be _____

A

cyclized

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12
Q

Cyclized carbohydrates can be found in two in two ring forms: ?

A
  1. Six-membered sugar ring - pyranose
  2. Five-membered sugar ring - furanose
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13
Q

Cyclization of glucose to glucopyranose involves the __ hydroxyl and the __ aldehyde. Cyclization renders C1 chiral, producing two stereoisomers, __ __ ___

A

C5, C1, α and β

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14
Q

What is the anomeric carbon?

A

The carbon that becomes chiral as a result of cyclization.

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15
Q

The __ and __ forms are anomers of each other

A

α - hydroxyl of anomeric carbon is below the plane of the sugar
β - hydroxyl of anomeric carbon is above the plane of the sugar

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16
Q

In solution, the α and β configurations interconvert by a process called ______

A

mutarotation

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17
Q

Mutarotation occurs through a ___ _____ and represents a change in ______

A

linear intermediate, configuration

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18
Q

In solution, glucose tends to be 2/3 __-_______, 1/3 __-______ and less than 1% _____

A

β-glucopyranose, α-glucopyranose, linear

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19
Q

Describe the cyclization of D-Fructose to Fructofuranose

A

Involves the C5 hydroxyl and the C2 ketone. Cyclization renders C2 chiral (anomeric carbon), producing α and β stereoisomers

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20
Q

True or False: fructose exists in both pyran and furan rings?

A

True

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21
Q

Linear forms of monosaccharides can be oxidized by..? The carbonyl group is oxidized to a ____ group

A

mild oxidizing agents like iron and copper. carboxyl

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22
Q

When the carbonyl group is oxidized to a carboxyl group, it allows for ______ of sugars present in blood or urine. Also defines the end of the sugar with the carbonyl carbon as being the ____ end

A

quantifications, reducing

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23
Q

What is a glycosidic bond, and what are the two types and how do they occur?

A

Primary structural linkage in all polymers of monosaccharides
* O-glycosidic bonds occur through oxygen
* N-glycosidic bonds occur through nitrogen

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24
Q

The end of the chain with a free anomeric carbon is called the ____ end of the polymer

A

reducing

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25
Q

What do the 4 components of the nomenclature of a disaccharide specify?

A
  1. The monosaccharides involved in the disaccharide.
  2. Their ring types (puran, furan).
  3. Their configurations (alpha or beta).
  4. Their linkages (C1-C4, etc).
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26
Q

Monosaccharides that have multiple hydroxyl groups means that there are many different ____ linkages are possible

A

glycosidic

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27
Q

Higher order carbohydrate structures are generated through the action of _______

A

glycosyltransferases

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28
Q

Glycosyltransferases use monosaccharides that are activated through..?

A

linkage with UDP

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29
Q

What are the 5 steps in determining disaccharide nomenclature?

A

1) Specify the configuration (alpha or beta) at the anomeric carbon of each monosaccharide.
2) Specify the ring form (furan or pyran) of each monosaccharide.
3) The non-reducing sugar has the suffix “osyl”.
4) The reducing sugar has the suffix “ose”.
5) Indicate in parentheses the two carbon atoms joined by the glycosidic bond with an arrow.

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30
Q

Lactose intolerant individuals have insufficient levels of the enzyme (lactase) that catalyzes the ______ of lactose into glucose and galactose

A

hydrolysis

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31
Q

True or False: polysaccharides have limited structures and functions?

A

False, polysaccharides have diverse structures and functions.

32
Q

What are some biological functions of polysaccharides?

A

Energy storage, structural roles, cushioning and lubrication

33
Q

What are homopolysaccharides?

A

Polymers containing a single type of monosaccharide

34
Q

What are heterosaccharides?

A

Polymers containing more than one type of monosaccharide

35
Q

True or False: both hetero and homopolysaccharides can be either unbranched or branched?

A

True

36
Q

Glucose is stored _____ in polymeric forms in both plants (starch) and animals (glycogen)

A

intracellularly

37
Q

True or False: starch and glycogen are both heavily hydrated structures?

A

True

38
Q

What is starch, and where is it found?

A

A mixture of two molecules, amylose (unbranched) and amylopectin (branched) and is found in plants and fungi.

39
Q

Where is glycogen stored?

A

Stored in liver and skeletal muscle of animals

40
Q

What is amylose?

A

A linear polymer of glucose residues through α(1-4) bonds

41
Q

What is amylopectin?

A

Consists of α(1-4) linked glucose residues with α(1-6) branch points every 24-30 residues

42
Q

Does amylose or amylopectin have a single reducing end?

A

They both have a single reducing end

43
Q

Does amylose or amylopectin have a single non-reducing end?

A

Amylose

44
Q

Does amylose or amylopectin have multiple non-reducing ends?

A

Amylopectin

45
Q

What is the structure of glycogen?

A

Structurally identical to amylopectin: consists of α(1-4) linked glucose residues with α(1-6) branch points but with a higher frequency of branch points (every 10 residues)

46
Q

Greater frequency of branching allows for _____ ______

A

rapid mobilization

47
Q

Glycogen is mobilized in times of need by ____ ______ which sequential cleaves glucose residues from non-reducing ends

A

glycogen phosphorylase

48
Q

Cellulose is the primary component of..?

A

plant cell walls (fiber)

49
Q

Which chemical compound accounts for over half of the carbon in the biosphere?

A

Cellulose

50
Q

What is the structure of cellulose?

A

Linear, homopolysaccharide of glucose residues. It has a linear arrangement of β(1-4) glycosidic residues.

51
Q

Cellulose has a linear arrangement of β(1-4) glycosidic residues. Can these bonds be cut by amylase?

A

No

52
Q

Chitin is the principal component of..?

A

hard exoskeletons (insects, lobsters, etc).

53
Q

What is the structure of chitin?

A

A linear, homopolysaccharide of N-acetylglucosamine residues

54
Q

What is the chemical difference between chitin and cellulose?

A

The replacement of hydroxyl group at C2 with acetylated amino group

55
Q

The β 1-4 linkages of cellulose and chitin allow formation of..?

A

long straight chains

56
Q

Fibrils are formed by _____ _____ that are linked through ____ _____. These fibers generate a rigid supportive structure of high ____ _____.

A

parallel chains, hydrogen bonds, tensile strength

57
Q

The α 1-4 linkages of starch and glycogen form a ___, ____ structure. This provides a compact, accessible storage structure of

A

hollow, helical, glucose

58
Q

Sugars are covalently linked to lipid molecules to form _____

A

glycolipids

59
Q

What is a central function of glycolipids?

A

Blood group antigens

60
Q

Different patterns of sugars presented on the surface of cells by the glycolipids help the body to discriminate..?

A

self from non-self

61
Q

Differences in the blood group antigens are critical for..?

A

blood transfusions

62
Q

What are glycoproteins? (x3)

A
  1. Proteins with covalently attached sugars.
  2. The protein constituent is the largest component by weight.
  3. Serve a variety of biological roles.
63
Q

What are proteoglycans? (x3)

A
  1. Protein component is linked to to a particular type of carbohydrate called a glycosaminoglycan
  2. The carbohydrate constituent is the largest component by weight.
  3. Often serve structural and lubricating functions
64
Q

Glycoproteins are proteins that undergo post-translational
______, which is the..?

A

glycosylation, addition of sugar groups

65
Q

About half of biological proteins are modified with sugar groups. These modifications regulate ___________ and often involve ___________ of sugar attachment.

A

the structure and function of the protein, complex and specific patterns

66
Q

In glycoproteins, the sugars are attached to either..?

A
  1. the amide nitrogen of the side chain of an asparagine (N-linked).
  2. the hydroxyl oxygen of the side chain of serine or threonine (O-linked).
67
Q

Erythropoietin (EPO) stimulates ___ _____ ____ production and has __ N-linked and __ O-linked glycosylation.

A

red blood cell, 3, 1

68
Q

EPO is highly effective in the treatment of _____

A

anemia (red blood cell deficiency)

69
Q

Extracellular space in tissues contains a gel-like material called the..?

A

Extracellular matrix (ground substance)

70
Q

What is the purpose of Ground Substance?

A

Holds cells together, provides a porous pathway for diffusion of nutrients/waste products and serves a cushioning function

71
Q

Extracellular matrix is a meshwork of fibrous proteins and
heteropolysaccharides called the ________

A

glycosaminoglycans

72
Q

True or False: Alpha-galactopyranose and beta-galactopyranose are anomers?

A

True

73
Q

True or False: does cellulose contain beta 1-4 linkages?

A

True

74
Q

For fructose in the furan ring form, which carbon is the anomeric carbon?

A

C2

75
Q

For glucose in the pyran ring form, which carbon is the anomeric carbon?

A

C1

76
Q

How many stereoisomers exist for glucose in the linear form?

A

16