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CHE 4341 Baylor (Dr. Jonklaas) > Unit 3.1 (carbs) > Flashcards

Unit 3.1 (carbs) Flashcards

1
Q

What are carbohydrates? What is their general formula?

A

Sugars that are polyhydroxyl (lots of OH’s) aldehydes and ketones. They are made up of Carbon and H2O subunits.

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2
Q

Describe the 3 classes of Carbohydrates (monosaccharides, oligosaccharides, and polysaccharides)

A

Monosaccharides - Single sugars freely soluble in water (sweet taste)
Oligosaccharides - Short chains of single sugars covalently linked
Polysaccharides - Long chains (hundreds or thousands) of single sugars covalently linked

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3
Q

Are all monosaccharides chiral?

A

Except for dihydroxyacetone, all monosaccharides are chiral

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4
Q

What standard reference compound is used for Fischer notation?

A

Glyceraldehyde

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5
Q

Are most naturally occurring carbohydrates L- or D- enantiomers?

A

Most are D-, although some L- do occur

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6
Q

How do you differentiate D vs L enantiomers in monosaccharides?

A
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7
Q

Which monosaccharides are diastereomers of each other?

A

Any two monosaccharides with the same number of carbon atoms would be considered diastereomers

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8
Q

What is an Epimer?

A

A special subset of diastereomers when 2 sugars differ only in the configuration around one carbon

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9
Q

Describe the general structure of D-ketoses

A

Same as for D-aldoses, except switch C1 C=O and C2 OH (results in one less chiral C)

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10
Q

What process occurs that changes a D-Aldose into a D-Ketose?

A

Tautomerization

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11
Q

Describe (in detail) hemiacetal and hemiketal formation.

A
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12
Q

What is an Anomer?

A
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13
Q

What structure is this?

A

Pyran Ring

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14
Q

Describe (in detail) the cyclization of Glucose

A

hemiacetal formation!

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15
Q

Define mutarotation

A

The interconversion in solution between alpha and Beta anomer forms via the open-chain structure

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16
Q

What is the predominant anomer of glucose in solution?

A

pyranose beta form

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17
Q

Describe (in detail) the cyclization of fructose

A

hemiketal formation!

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18
Q

What structure is this?

A

Furan ring

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19
Q

What does drawing the amino sugar form involve?

A

Drawing the amino sugar form simply involves replacing the C 2’ OH group and substituting an amino NH2 group in its place

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20
Q

What does drawing the N-acetyl sugar from involve?

A

Drawing the N-acetyl sugar simply involves adding an acetyl group to the amino NH2 group

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21
Q

How would you draw a 2’ deoxy sugar?

A

Just convert OH to H at a specified (2’) position

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22
Q

Describe (in detail) acetal and ketal formation

A

Irreversible!

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23
Q

How are glycosidic linkages formed?

A

Through acetal formation

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24
Q

How are glycosidic linkages named?

A

Based on the anomeric carbon in the 1st sugar & the C-OH position # of the 2nd sugar

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25
Q

Describe the summary table of Disaccharides (in detail)

A
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26
Q

Why is it significant if the anomeric bond is alpha or beta?

A

Anomeric bond, whether alpha or beta, greatly influences the shape of the molecule, which in tun influences enzyme activity on disaccharide

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27
Q

What do monosaccharides and disaccharides taste like?

A

Taste sweet

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28
Q

Describe the physical properties of mono/disaccharides

A

They undergo hydrogen bonding with themselves, as well as with water; They are solids at room temperature and very soluble in water; Highly concentrated solutions of monosaccharides like honey, maple syrup, and molasses are very viscous liquids

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29
Q

Give an overview summary of Acid/Base catalyzed tautomerism

A

Occurs through Enediol intermediate!!

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30
Q

Give an overview summary of reduction of aldoses to alditols

A

Reduction of C=O to alcohol with NaBH4
Reduces aldoses and ketoses to alditols

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31
Q

What are alditols?

A

When the C1=O is reduced to an alcohol (“sugar alcohols”) - These have some sweetness, but are lower in calories (used in gum)

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32
Q

What is the difference between Glucaric Acids and Uronic Acids? (oxidation of sugars with strong [O] agents.

A
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33
Q

What is D-glucaronic acid important for?

A

It is a component of polysaccharide hyaluronic acid (vitreous humor of eye)

34
Q

Describe (in detail) Oxidation of sugars with mild [O] agent

A
35
Q

Define a Reducing Sugar

A

Any sugar that can reduce a mile oxidizing reagent like Tollen’s (requires sugar to be in open chain form so that aldehyde [HC=O] is present

36
Q

What mild oxidizing reagents are used to test for reducing sugars? (3)

A

1) Tollen’s Reagent
2) Benedict’s Test
3) Fehling’s Test

37
Q

Describe (in detail) non-reducing sugars

A
38
Q

Describe N Glycosidic bonds

A
39
Q

Describe Complex Carbohydrates

A

Chains of 3 or more single sugar molecules linked together (includes starches & cellulose)

40
Q

What are the functions of polysaccharides?

A

Storage, structure, recognition

41
Q

What is the difference between homopolysaccharides vs. heteropolysaccharides

A
42
Q

What is starch?

A

A plant glucose (energy) storage polysaccharide

43
Q

What are the two forms of starch?

A

Amylose and Amylopectin (most starch is 10-30% amylose and 70-90% amylopectin)

44
Q

What is the difference between amylose and amylopectin? (describe in detail)

A
45
Q

Why are branches important in polysaccharides like amylopectin?

A

Branches allow for quick release (or storing) of glucose units for (or from) metabolism

46
Q

Describe (in detail) the reaction that releases glucose from a starch polysaccharide

A
47
Q

Describe the basis of the “starch” iodine test

A
48
Q

Describe (in GREAT detail) the process of the digestion of starch. Include enzymes, bonds broken, and subunits that result from the process.

A
49
Q

Describe (in detail) how glucose is absorbed into a cell (GLUT4)

A
50
Q

What is Glycogen? Compare/Contrast it to amylopectin

A

The glucose (energy) storage device in animals!

51
Q

What reaction is responsible for the releasing of glucose from glycogen?

A

The same reaction that accounts for the release of glucose from starch!!!

52
Q

What is the most abundant STRUCTURAL POLYSACCHARIDE on earth?

A

Cellulose

53
Q

Describe the structure of Cellulose

A

Linear and unbranched, containing 10,000 to 15,000 D-glucose units that are linked with a B(1-4) linkage; Structure consists of several chain slying side by side, resulting in fibers with high tensile strength (water insoluble)

54
Q

Does Cellulose produce a positive Iodine Test?

A

No, it produces a negative iodine test because it is linear. Because it does not cyclize, there is nowhere for the Iodine to bind

55
Q

Why is it significant that cellulose is a component of insoluble (dietary) fiber?

A

Promotes regular bowel movement

56
Q

What enzyme is required to digest Cellulose? What organisms have this enzyme?

A
57
Q

What is the second most abundant polysaccharide on earth? Describe its structure and glycosidic bonds.

A
58
Q

What is a Glycoconjugate?

A

Carb + Lipid/Protein (carb. covalently linked to nonsugar moiety)

59
Q

Describe Peptidoglycan (Murein)

A

Glycoconjugate
Bacterial Cell Wall
Provides strength and rigidity for the organism (prevents osmotic lysis)
Determines the gram staining characteristic of the bacteria

60
Q

Describe the structural characteristics of bacterial cell wall

A

A structural glycoconjugate
Bacterial cell walls are heteropolysaccharide of alternating (B1-4) linked NAG & NAM
Has polypeptide cross-links

61
Q

Describe the last step in Peptidoglycan synthesis

A
62
Q

How do Penicillin drugs work?

A

Penicillins resemble D-Ala - D-Ala substrate of transpeptidase (enzyme necessary for the last step of the formation of bacterial cell walls) - Penicillins are irreversible inhibitors of transpeptidase
Penicillin Drugs have B-lactam rings (structurally similar to 2 D-Ala’s)
Stops bacterial cell wall synthesis

63
Q

What are some examples of B-Lactam antibiotics

A
64
Q

What is unique about a Staph infection?

A

Staph strains are resistant to ALL penicillins

65
Q

Describe Antibiotic Resistance (B-lactamases)

A

B-Lactamases are bacterial enzymes which hydrolyse B-lactam rings
Defense because they destroy B-lactam antibiotics

66
Q

What is an example of a B-lactamase inhibitor?

A

Clavulanic Acid - reacts with B-lactamases, irreversibly inhibitting them (thus, they cannot hydrolyze B-lactam antibiotics & efficacy of drugs is restored)

67
Q

Describe Glycoproteins

A

Glycoconjugate
Proteins with covalently linked oligo- and polysaccharides
Modified proteins include structural proteins, enzymes, receptors, transport proteins, and immunoglobins

68
Q

What are the 2 types of Glycoproteins?

A
  1. O-linked to Ser, Thr, hydroxyLys, hydroxyPro
  2. N-linked to Asn (only) - longer chains
69
Q

When does carb attachment take place for glycoproteins?

A

Carb attachment is co/post translational modification (occurs in ER & golgi)

70
Q

Define the significance of Sialic acid in glycoproteins

A

Sialic acid is often found as a terminal residue of oligosaccharide chains of glycoproteins
Imparts negative charge to glycoproteins, because carboxyl group is negatively (-) charged a physiological pH

71
Q

Describe Glycosaminoglycans (GAGs)

A

A component of Proteoglycans
Linear polysaccharides consisting of a repeating disaccharide (normally an acetylated amino sugar alternating with a uronic acid)
Often negatively (-) charged from added sulfate and uronic acid (COO-)

72
Q

What are the diverse function of GAGs?

A

Heparin: Stop blood clotting
Hyaluronate: Eye juice and knee oil
Chondroitins/Keratans: Connective tissue

73
Q

What are proteoglycans?

A

Glycoproteins whos carb. moieties are linear, O-linked GAGs

74
Q

What is the role of proteoglycans?

A

Either fill extracellular matrix (ECM) or “decorate” cell membrane
Contribute flexibility/resiliency and organization/physical properties

75
Q

What are 2 Proteoglycans that are prominent in the ECM? Describe their structure.

A

Aggrecan and Versican (structural components of ECM)
Both have a bottle-brush structure

76
Q

What is unique about Proteoglycans found in connective tissue?

A

“SHOCK ABSORBERS”
Highly branched = gel; GAGs give ability to absorb/release H2O
Account for shock absorption & lubricant properties (“knee oil”)

77
Q

What are syndecans? What is their role?

A

Cell surface proteoglycans
Involved in signaling regulation

78
Q

What are Lectins?

A

PROTEINS (not carbs)
= Proteins that bind specific cell surface carbohydrate patterns
Play a role in biological recognition involving cells and proteins

79
Q

What is one example of a Lectin? What is it important for?

A

Mannan-binding Lectin (MBL) - Binds cell surface carbohydrates of disease-causing microorgansims, promoting their phagocytosis
***Some bacteria & viruses (influenza) use lectins to attach themselves to the cells of the host organism during infection

80
Q

What are the two classes of surface protein?

A

Hemaglutinin (HA) (a lectin) and Neuraminidase (NA)

81
Q

Describe (in detail) how a flu infection works

A

For a flu virus to penetrate the cells of the respiratory tract, its thron-like hemaclutinin (HA) molecules must dock to N-acetylneuraminic acid (a siliac acid) molecules on the surface of the host cell
Causes the host cell to ingest the virus

82
Q

How does Tamiflu work?

A

Tamiflu is a Competitive Inhibitor of Neuraminidase (resembles siliac acid)
Stops infection!

CHE 4341 Baylor (Dr. Jonklaas) (14 decks)

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