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SP MCAT Biochem > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

Trioses

A
  • simplest monosaccharide

- contain 3 Carbons

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2
Q

Tetroses

A

contain 4 Carbons

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3
Q

Pentoses

A

contain 5 Carbons

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4
Q

Hexoses

A

contain 6 Carbons

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5
Q

Aldoses

A
  • carbs that contain an aldehyde group as their most oxidized functional group
  • aldehyde carbon is C1 and can participate in glycosidic linkages
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6
Q

Ketoses

A
  • carbs that contain a ketone as their most oxidized functional group
  • “keto” glucose
  • fructose is this type of carb
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7
Q

Stereoisomers

A
  • optical isomers
  • compounds with same chemical formula but differ in spatial arrangement of their component atoms
  • include diastereomers and enantiomers
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8
Q

Enantiomers

A
  • isomerism between stereoisomers that are non-identical
  • non-superimposable mirror images of each other
  • all chiral carbons are reversed
  • Ex. D- and L- sugars
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9
Q

Absolute Configuration

A
  • use of L- and D- assignment
  • reference the C above the CH2OH group to determine L or D assignment
  • L: -OH group on C points left
  • D: -OH group on C points right
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10
Q

Relative Configuration

A
  • use of R and S assignment
  • optical activity
  • if stereocenter of molecule is R then it is (+)
  • if stereocenter of molecule is S then it is (-)
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11
Q

Diastereomers

A
  • sugars that differ at one or more chiral carbons

- non-superimposable, not mirror images

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12
Q

Epimers

A
  • diastereomer subtype (isomers are NOT mirror images)
  • sugars differ at only one chiral carbon
  • Ex. D-galactose is a C4 Epimer of glucose
  • Ex. D-Mannose is a C2 Epimer of glucose
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13
Q

Anomers

A
  • epimer subtype
  • special class of C1 epimers
  • anomeric carbon is the one that has -OH group pointing up in one epimer and -OH group pointing down in the other epimer
  • labeled as alpha or beta
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14
Q

Alpha-Anomer

A

-OH on the anomeric carbon is trans to the free -CH2OH group (axial and down)

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15
Q

Beta-Anomer

A

-OH on the anomeric carbon is cis to the free -CH2OH group (equatorial and up)

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16
Q

How does the side groups change in a monosaccharide when you convert it from its straight chain Fischer projection to the Hawthorn Projection?

A

any group on the right in the Fischer Projection will point down in the Hawthorn Projection

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17
Q

Mutarotation

A
  • spontaneous change of configuration between the alpha or beta anomer because of free rotation of the single bond between C1 and C2
  • occurs more rapidly when rxn is catalyzed by an acid or base
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18
Q

Monosaccharides

A
  • contain alcohols and either aldehydes or ketones

- single carbohydrate units

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19
Q

Reduction of Monosaccharides

A
  • decreases the number of C-O bonds

- increases the number of C-H bonds

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20
Q

Oxidation of Monosaccharides

A
  • increases the number of C-O bonds

- decreases the number of C-H bonds

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21
Q

What monosaccharide forms when the hydroxyl group on the anomeric carbon is oxidized?

A

Lactone

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22
Q

Reducing Sugars

A
  • monosaccharides with a a hemiacetal ring
  • must have the property of being able to be oxidized
  • capable of transferring hydrogens (electrons) to other compounds
  • the reducing end consists of a hemiacetal
  • Ex. aldoses
23
Q

What two reagents can be used to detect the presence of a reducing sugar?

A
  • Tollen’s Reagent

- Benedict’s Reagent

24
Q

Tollen’s Reagent

A

[Ag(NH3)2]+

-in the presence of a reducing sugar (aldehydes) the reagent is reduced and produces a silvery mirror

25
Q

Benedict’s Reagent

A

Cu(OH)2

  • identifies reducing sugars that have free hemiacetals
  • in the presence of a reducing sugar, a red precipitate of Cu2O will form
26
Q

Tautomerization

A
  • rearrangement of bonds in a compound
  • usually involves moving a H and forming a double bond
  • occurs when a ketose (nonreducing sugar) is converted to an enol then aldose product (reducing sugar)
27
Q

Enol

A

an organic compound that contains a hydroxyl group bonded to a carbon atom having a double bond and that is usually characterized by the grouping C=C(OH)

28
Q

Deoxy Sugar

A

sugars with a -H group replacing an -OH group at the 2’ C

29
Q

Esterification of Monosaccharides

A

reaction by which a hydroxyl group reacts with either a carboxylic acid or a carboxylic acid derivative to form an ester

30
Q

Phosphorylation of Monosaccharides

A
  • reaction in which a phosphate ester is formed by transferring a phosphate group from ATP onto a sugar
  • example of esterification – hydroxyl group acts as nucleophile and attacks terminal phosphate group in ATP, producing a substitution reaction at C6 (now a glycosidic linkage between C6 and phosphate group
31
Q

Acetals (Ketals)

A

formed by the reaction of hemiacetals (hemiketals) with alcohols under acidic conditions

32
Q

Glycoside

A
  • molecule that contains a bond between a functional group and a carbon in a sugar
  • bond is termed glycosidic linkage
33
Q

Glycosidic Linkages

A
  • formed when an alcohol functional group attached to an anomeric carbon of a sugar reacts with another alcohol functional group
  • linkages join monosaccharides together to create disaccharides or polysaccharides
34
Q

What type of reaction occurs during glycoside formation?

A

dehydration reaction

35
Q

Disaccharides

A

two monosaccharides linked via glycosidic bonds

36
Q

Which direction do alpha-glycosidic linkages point?

A

down

37
Q

Which direction do beta-glycosidic linkages point?

A

up

38
Q

Lactose

A

Lauren Gets Gold
Lactose = Glucose + Galactose

  • disaccharide
  • formed in reaction between galactose and glucose with a beta-1,4 glycosidic linkage
  • galactose-beta-1,4-glucose
39
Q

Sucrose

A

Sarah Gets Fat
Sucrose = Glucose + Fructose

  • disaccharide
  • formed in a reaction between glucose and fructose with an alpha-1,2 glycosidic linkage
  • glucose-alpha-1,2-fructose
40
Q

Maltose

A
  • disaccharide
  • formed in a reaction between 2 glucose molecules with an alpha-1,4 glycosidic linkage
  • glucose-alpha-1,4-glucose
41
Q

Polysaccharides

A

long chains of monosaccharides linked together by glycosidic bonds

42
Q

Cellulose

A
  • polysaccharide
  • main substance in plant cell walls
  • chain of beta-D-glucose molecules linked by beta-1,4 glycosidic bonds
  • H bonds hold the polymer chains together
43
Q

Can humans digest cellulose?

A

No, we only have the enzyme necessary to cleave alpha-glycosidic linkages

44
Q

Starches

A
  • polysaccharides
  • digestible by humans
  • linked alpha-D-glucose monomers
45
Q

Amylose

A
  • starch
  • plant storage form of starch
  • linear glucose polymer linked via alpha-1,4 glycosidic bonds
46
Q

Amylopectin

A
  • starch
  • contains alpha-1,4 glycosidic linkages between glucose monomers and every 20-30 glucoses there is branching due to alpha-1,6 glycosidic linkages
  • easier to digest than amylose b/c of branched structure
47
Q

What reagent can test for the presence of starch?

A

iodine

48
Q

Amylase

A
  • digestive enzyme (secreted by the salivary glands, and by the pancreas –> goes to small intestine)
  • cleaves alpha-1,4 glycosidic bonds
49
Q

Beta-Amylase

A

cleaves amylose at the non-reducing end of the polymer to yield maltose

50
Q

Alpha-Amylase

A
  • hydrolyses alpha bonds of large, alpha-linked polysaccharides, such as starch and glycogen, yielding glucose and maltose
  • major form of amylase found in humans and other mammals
51
Q

Glycogen

A
  • polysaccharide
  • carbohydrate storage unit in animals
  • made up of alpha-1,4 linked glucose molecules with apha-1,6 linkage occurring every 10 glucose monomers making it highly branched
  • more soluble in solution and easy to digest due to highly branched nature
52
Q

Glycogen Phosphorylase

A
  • cleaves glucose from the non-reducing end of a glycogen branch and phosphorylates it
  • produces glucose 1-phosphate
53
Q

What kind of sugar is sucrose?

A

NON-REDUCING SUGAR!

SP MCAT Biochem (16 decks)

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