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

Unit 3.1 (carbs) Flashcards

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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
Describe the summary table of Disaccharides (in detail)
26
Why is it significant if the anomeric bond is alpha or beta?
Anomeric bond, whether alpha or beta, greatly influences the shape of the molecule, which in tun influences enzyme activity on disaccharide
27
What do monosaccharides and disaccharides taste like?
Taste sweet
28
Describe the physical properties of mono/disaccharides
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
29
Give an overview summary of Acid/Base catalyzed tautomerism
Occurs through Enediol intermediate!!
30
Give an overview summary of reduction of aldoses to alditols
Reduction of C=O to alcohol with NaBH4 Reduces aldoses and ketoses to alditols
31
What are alditols?
When the C1=O is reduced to an alcohol ("sugar alcohols") - These have some sweetness, but are lower in calories (used in gum)
32
What is the difference between Glucaric Acids and Uronic Acids? (oxidation of sugars with strong [O] agents.
33
What is D-glucaronic acid important for?
It is a component of polysaccharide hyaluronic acid (vitreous humor of eye)
34
Describe (in detail) Oxidation of sugars with mild [O] agent
35
Define a Reducing Sugar
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
What mild oxidizing reagents are used to test for reducing sugars? (3)
1) Tollen's Reagent 2) Benedict's Test 3) Fehling's Test
37
Describe (in detail) non-reducing sugars
38
Describe N Glycosidic bonds
39
Describe Complex Carbohydrates
Chains of 3 or more single sugar molecules linked together (includes starches & cellulose)
40
What are the functions of polysaccharides?
Storage, structure, recognition
41
What is the difference between homopolysaccharides vs. heteropolysaccharides
42
What is starch?
A plant glucose (energy) storage polysaccharide
43
What are the two forms of starch?
Amylose and Amylopectin (most starch is 10-30% amylose and 70-90% amylopectin)
44
What is the difference between amylose and amylopectin? (describe in detail)
45
Why are branches important in polysaccharides like amylopectin?
Branches allow for quick release (or storing) of glucose units for (or from) metabolism
46
Describe (in detail) the reaction that releases glucose from a starch polysaccharide
47
Describe the basis of the "starch" iodine test
48
Describe (in GREAT detail) the process of the digestion of starch. Include enzymes, bonds broken, and subunits that result from the process.
49
Describe (in detail) how glucose is absorbed into a cell (GLUT4)
50
What is Glycogen? Compare/Contrast it to amylopectin
The glucose (energy) storage device in animals!
51
What reaction is responsible for the releasing of glucose from glycogen?
The same reaction that accounts for the release of glucose from starch!!!
52
What is the most abundant STRUCTURAL POLYSACCHARIDE on earth?
Cellulose
53
Describe the structure of Cellulose
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
Does Cellulose produce a positive Iodine Test?
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
Why is it significant that cellulose is a component of insoluble (dietary) fiber?
Promotes regular bowel movement
56
What enzyme is required to digest Cellulose? What organisms have this enzyme?
57
What is the second most abundant polysaccharide on earth? Describe its structure and glycosidic bonds.
58
What is a Glycoconjugate?
Carb + Lipid/Protein (carb. covalently linked to nonsugar moiety)
59
Describe Peptidoglycan (Murein)
Glycoconjugate Bacterial Cell Wall Provides strength and rigidity for the organism (prevents osmotic lysis) Determines the gram staining characteristic of the bacteria
60
Describe the structural characteristics of bacterial cell wall
A structural glycoconjugate Bacterial cell walls are heteropolysaccharide of alternating (B1-4) linked NAG & NAM Has polypeptide cross-links
61
Describe the last step in Peptidoglycan synthesis
62
How do Penicillin drugs work?
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
What are some examples of B-Lactam antibiotics
64
What is unique about a Staph infection?
Staph strains are resistant to ALL penicillins
65
Describe Antibiotic Resistance (B-lactamases)
B-Lactamases are bacterial enzymes which hydrolyse B-lactam rings Defense because they destroy B-lactam antibiotics
66
What is an example of a B-lactamase inhibitor?
Clavulanic Acid - reacts with B-lactamases, irreversibly inhibitting them (thus, they cannot hydrolyze B-lactam antibiotics & efficacy of drugs is restored)
67
Describe Glycoproteins
Glycoconjugate Proteins with covalently linked oligo- and polysaccharides Modified proteins include structural proteins, enzymes, receptors, transport proteins, and immunoglobins
68
What are the 2 types of Glycoproteins?
1. O-linked to Ser, Thr, hydroxyLys, hydroxyPro 2. N-linked to Asn (only) - longer chains
69
When does carb attachment take place for glycoproteins?
Carb attachment is co/post translational modification (occurs in ER & golgi)
70
Define the significance of Sialic acid in glycoproteins
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
Describe Glycosaminoglycans (GAGs)
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
What are the diverse function of GAGs?
Heparin: Stop blood clotting Hyaluronate: Eye juice and knee oil Chondroitins/Keratans: Connective tissue
73
What are proteoglycans?
Glycoproteins whos carb. moieties are linear, O-linked GAGs
74
What is the role of proteoglycans?
Either fill extracellular matrix (ECM) or "decorate" cell membrane Contribute flexibility/resiliency and organization/physical properties
75
What are 2 Proteoglycans that are prominent in the ECM? Describe their structure.
Aggrecan and Versican (structural components of ECM) Both have a bottle-brush structure
76
What is unique about Proteoglycans found in connective tissue?
"SHOCK ABSORBERS" Highly branched = gel; GAGs give ability to absorb/release H2O Account for shock absorption & lubricant properties ("knee oil")
77
What are syndecans? What is their role?
Cell surface proteoglycans Involved in signaling regulation
78
What are Lectins?
PROTEINS (not carbs) = Proteins that bind specific cell surface carbohydrate patterns Play a role in biological recognition involving cells and proteins
79
What is one example of a Lectin? What is it important for?
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
What are the two classes of surface protein?
Hemaglutinin (HA) (a lectin) and Neuraminidase (NA)
81
Describe (in detail) how a flu infection works
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
How does Tamiflu work?
Tamiflu is a Competitive Inhibitor of Neuraminidase (resembles siliac acid) Stops infection!

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

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