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Organic Chemistry > Chapter 6 - Carbohydrates > Flashcards

Chapter 6 - Carbohydrates Flashcards

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1
Q

Describe Ruff degradation

A

It decreases the chain of an aldose by decarboxylation. The aldehyde is first oxidized into carboxylic acid and deprotonated by 1) Br2, H2O, 2) Ca(OH)2, H2O. Then the carboxylic acid is oxidized into carbon dioxide by peroxide in the presence of a ferric cation catalyst (H2O2, Fe3+). Carbon dioxide leaves and decreases the chain length by one carbon.

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2
Q

D-Mannose structure

A

D-mannose: man’s gun (middle and index finger of right hand as barrel)

L-mannose: man’s gun (middle and index finger of left hand as barrel)

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3
Q

When nitric acid (HNO3) is reacted with an aldohexose, what is the product? What is the purpose of using this reaction?

A

Nitric acid is an oxidizing agent that can oxidize both terminal carbons of an aldohexose (aldehyde and alcohol) into carboxylic acids. This is a test for optical activity.

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4
Q

What makes the strucure of cellulose so uniform?

A

It is linear and exhibits hydrogen bonding.

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5
Q

What is mutarotation?

A

conversion from one anomer into the other

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6
Q

How does the chirality of the penultimate carbon in carbohydrates determine D/L status?

A

If the penultimate carbon has R-stereochemistry it will be the D-isomer. If it has S-stereochemistry it will be the L-isomer.

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7
Q

What is the difference between ketoses and aldoses?

A

ketoses = ketone sugars

aldoses = aldehyde sugars

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8
Q

In naming disaccharides, how do the component names differ?

A

The left sugar is considered a subtituent on the right sugar, so it gets an “osyl” suffix, while the right sugar gets an “oside” suffix.

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9
Q

To form a cyclic sugar, which portions undergo reaction in the straight chain form? What is formed at the anomeric carbon?

A

A hydroxyl group attacks the carbonyl carbon yielding a hemiacetal/hemiketal.

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10
Q

How do the hydroxyl groups on each side of a Fischer projection relate to their up/down position on a Haworth projection?

A

If they are on the right, they will be down. If they are on the left, they will be up (“downright uplefting”).

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11
Q

D-Fructose structure

A

D-Fructose: ketose of glucose

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12
Q

Basic formula of monosaccharides

A

CnH2nOn

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13
Q

What is the purpose of the Tollen’s test and what does it use?

A

It uses silver ion reacted with an oxidizable sugar (either an aldose or ketose). The silver ion is reduced to silver metal and forms a silver mirror on the walls of the reaction vessel. The sugar is oxidized. If it is an aldose, it will oxidize quickly (positive test). If it is a ketose, it will take a bit of time.

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14
Q

D-Galactose structure

A

D-galactose: C-4 epimer of glucose

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15
Q

D-Ribose structure

A

D-ribose: ribose is all-right

L-ribose: ribose is all-left

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16
Q

What is a nucleoside?

A

nitrogenous base + sugar

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17
Q

Is glycolysis oxidative or reductive?

A

oxidative

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18
Q

What is a six-membered carbohydrate ring called?

A

pyranose

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19
Q

What is the positive of having so many steps and intermediates in glycolysis?

A

Intermediate products can be used in other pathways.

20
Q

In glycoslysis, how many net ATP are formed, how many NAD+ are required, and how many products are formed?

A
  • 2 net ATP are formed (release of energy)
  • 2 NAD+ are required (oxidative)
  • 2 pyruvate are formed
21
Q

Pyruvate can undergo fermentation to produce what? What type of reaction is this?

A

lactate (its ketone group is reduced to an alcohol)

22
Q

Phenylhydrazine structure

A
23
Q

How do epimers differ from anomers?

A

Anomers vary in chirality at the most oxidized carbon while epimers vary in chirality at any one of the less oxidized carbons.

24
Q

In a ketose-aldose isomerization or conversion between C-2 epimers, what intermediate is formed?

A

enediol

25
Q

Equation: # of stereoisomers

A

2n

n = number of chrial centers

26
Q

Osazone test: when 3 equivalents of phenyl hydrazine are reacted with either an aldose or 2-ketose, what is the product? What is the purpose of this test?

A

Carbon 1 and 2 imines (an osazone)

  • substitution to form an imine at the carbonyl
  • oxidation of alcohol into carbonyl
  • substitution to form another imine at the new carbonyl

This tests for C-2 epimers, since they will form the same product.

27
Q

What is the difference between an alpha and beta anomer?

A

The alpha anomer has its anomeric hydroxyl group on the opposite side of the ring (trans) as the CH2OH group.

The beta anomer has its anomeric hydroxyl group on the same side of the ring (cis) as the CH2OH group.

28
Q

Pyruvate can undergo reduction by yeast and bacteria to form what?

A

carbon dioxide and ethanol

29
Q

In a cyclic sugar, which carbon is the most oxidized?

A

the anomeric carbon

30
Q

Pyruvate can be oxidized by NAD+ to form what?

A

carbon dioxide and Acetal CoA

31
Q

Describe the Kiliani-Fischer synthesis

A

It increases the carbon chain of an aldose by one carbon. The new carbon is added as a cyano group at the aldehyde end (aldose reacted with KCN). It is then reduced to an imine and hydrolyzed, converting the cyano group into an aldehyde (1. H2/Pd-BaSO4, 2. H20/H+). The result is two aldose epimers with an addition carbon in a major-minor mixture.

32
Q

How do the blood types differ in relation to carbohydrates?

A

An oligosaccharide is bound to the amino terminal of a protein on the surface of a red blood cell that functions as an antigenic determinant. In type O, only 3 sugars make up the oligosaccharide, whereas type A and B have 4 sugars that make up the oligosaccharide. A and B differ in the 4th sugar.

33
Q

When ATP is hydrolyzed, how much energy is released?

A

7.3 kcal/mole

34
Q

What are the 3 main stages of glycolysis?

A

1) Glucose is converted into two equivalents of glyceraldehyde-3-phosphate
2) Glyceraldehyde-3-phosphate is converted into 3-phosphoglycerate
3) 3-phosphoglycerate is converted into pyruvate

35
Q

Are D or L carbohydrates found in biological molecules?

A

D

36
Q

Which step in glycolysis is irreversible and committed?

A

Step I: phosphorylation of glucose, it releases energy and uses ATP

37
Q

What is a five-membered carbohydrate ring called?

A

furanose

38
Q

What is a hallmark of irreversible reactions?

A

They are typically exergonic (ΔG < 0). They are also typically regulated (ex: requiring of ATP).

39
Q

What type of reaction takes place in order to form a glycosidic linkage?

A

Dehydration reaction: hydroxyl group from one sugar attacks the anomeric carbon of another

40
Q

D-Glucose structure

A

D-glucose: Fuck glucose (right hand)

L-glucose: Fuck glucose (left hand)

41
Q

What is the C:H:O ratio in carbohydrates?

A

1:2:1

42
Q

What is the structure of cellulose? Can we digest it?

A

It is a linear, β-linked polysaccharide. We cannot digest it because we lack the enzyme that cleaves β-glycosidic linkages.

43
Q

What is the only oxidation step in glycolysis?

A

Step VI: oxidative phosphorylation of G-3-P into 1,3-bisphosphoglycerate

44
Q

Is β- or α-D-glucopyranose more stable and why?

A

β-D-glucopyranose is more stable because in its chair conformation, all of its substituents are equatorial.

45
Q

Imine structure

A
46
Q

When two monosaccharides link up to form a disaccharide, what functional group is formed at the anomeric carbon?

A

ketal or acetal

Organic Chemistry (6 decks)

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