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Biochemistry I > Biochemistry Midterm 2.4 - Carbohydrates > Flashcards

Biochemistry Midterm 2.4 - Carbohydrates Flashcards

1
Q

glycome and glycode

A

genome of sugars
sugar code designated by monosaccharides, oligosaccharides, polysaccharides and complex glycoconjugates

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2
Q

glycan

A

polysaccharides made up of monosaccharides linked by glycosidic bonds

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3
Q

aldose vs ketose

A

aldose - aldehyde containing sugar (=O on the end)
ketose - ketone containing sugar (=O anywhere but the end)

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4
Q

oligosaccharides

A

3-10 monomers long
linked onto lipids and proteins

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5
Q

smallest carbohydrate and its constitutional isomer
reference compound for naming D and L sugars

A

3 carbons: glyceraldehyde (aldiose) and dihydroxyacetone (ketiose)
reference compound is glyceraldehyde

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6
Q

basic monosaccharide nomenclature

A

n = 3-7 –> tri, tetr, pent, hex, hept
sugar = ose, aldo or keto
aldotriose, ketotetrose

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7
Q

D vs L enantiomers

A

Dextro: OH of the chiral carbon farthest from the carbonyl group is on the right
Levo: OH of the chiral carbon farthest from the carbonyl group is on the left

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8
Q

number of stereoisomers formula

A

2^n
n = # of chiral centers

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9
Q

epimer definition
equation for # of epimers

A

stereoisomers that differ in only one chiral carbon orientation
type of diastereomer
# of chiral carbons - 1

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10
Q

diastereomers

A

differ in chiral centers but are not enantiomers
non-mirror image
have different physical properties
requires 2+ chiral centers

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11
Q

constitutional isomer’
stereoisomer

A

same formula different connectivity
same formula, same connectivity, different spatial arrangement

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12
Q

4 carbons D-aldoses diastereomers

A

D-erythrose
D-threose

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13
Q

5 carbon D-aldoses stereoisomers

A

D-ribose (standard 5 carbon sugar)
D-arabinose
D-xylose
D-lyxose

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14
Q

six carbon D-aldoses stereoisomers

A

D-glucose and D-manose are epimers of each other on C-2
structure D-glucose (C-2 OH is on right)
D-glucose and D-galactose are epimers of each other on C-4
Glucose is standard 6 carbon sugar

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15
Q

3 carbon D-ketose

A

dihydroxyacetone
no chiral center

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16
Q

4 carbon D-ketose

A

D-Erythrulose

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17
Q

5-carbon D-ketoses

A

D-Ribulose
D-Xylulose
epimers

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18
Q

6 carbon D-ketoses

A

D-fructose (C3 OH is on left)
ketose form of glucose

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19
Q

how hemiacetals and hemiketals are formed and what happens

A

hemiacetal is formed from an aldose (pyranose)

hemiketal is formed from a ketose (furanose or pyranose)

in both cases the carbonyl carbon is reduced to an alcohol and creates new C1 chiral center

20
Q

pyranose
furanose

A

pyranose: sugar with 6 membered ring
more stable than furanose

furanose: sugar with 5 membered ring

21
Q

alpha vs beta

A

Alpha is C1 carbon OH group faces down (trans)
Beta is C1 carbon OH group facing up (cis)
both in relation to OH group attached to C on otherside side of O atom in the ring

22
Q

anomeric carbon

A

The anomeric carbon is the carbonyl carbon atom of a sugar which is involved in ring formation
becomesC1 chiral center
attached OH group is determiner of alpha or beta
aka differ in configuration around hemiacetal/hemiketal carbon

23
Q

mutarotation

A

conversion between alpha and beta anomers

24
Q

chair conformations

A

preferred by pyranoses
requires energy to change conformation

25
Q

change of conformation vs configuration

A

change of conformation requires no break of bonds
change of configuration requires breaking bonds

26
Q

how to recognize fructose vs. ribose?

A

it is a ketose, it has CH2OH on 1’ and 5’ carbons
ribose is an aldose, it has CH2OH on only 5’ C, and an OH on 1’

27
Q

glycoside definition

A

A glycoside is an acetal formed between a sugar anomeric carbon hemi-acetal and an alcohol, which may be part of a second sugar.

28
Q

Glucose fischer structure

A
29
Q

definition of a free anomeric carbon

A

carbon attached to an OH, but no bonds to other molecules
once it makes a glycosidic bond, it is no longer reducing

30
Q

types of tests to check for reducing ends

A

Fehling test: Cu2+ reduced to Cu+ (color change from blue to brown)
Tollen’s Test: Ag+ reduced to Ag
Enzymatic test: uses glucose oxidase which produces ROOR which oxidizes organic molecules into highly colored compounds which can be measured colormetrically

31
Q

acetal/ketal are

A

glycosidic bonded monosaccharide at the anomeric carbon that is more stable and less reactive (non reducing)
hemiacetal –> acetal
hemiketal –> ketal

32
Q

naming disaccharides

A

First sugar: 1) alpha/beta 2) D/L 3) monosaccharide prefix (fructo/galacto/gluco/ribo) 4) furano/pyrano 5) “syl” suffix
(carbon # –> carbon #)
Second Sugar: 1) alpha/beta 2) D/L 3) prefix 4) furano/pyrano 5) suffix “side”

33
Q

common names for disaccharides

A

maltose - glucose x2
sucrose - glucose + fructose
lactose - galactose + glucose

34
Q

ether bond vs ester bond vs phosphoester vs phosphodiester
examples of each

A

ether - R-O-R (ex. glycosidic)
ester - R-C(=O)-OR (ex. triacylglycerides)
phosphoester - R-O-P (ex. phosphatidate)
phosphodiester - R-O-P-O-R (ex. nucleic acids)

35
Q

chemical modifications of monosaccharides

A

add groups OTHER THAN H, C, O
phosphorylation - adding phosphate
amidation - adding NH2 to replace OH
acetylation - adding OCH3 double bonded
oxidation - increase C-heteroatom bonds and decrease in C-H bonds
methylation - adding CH3

36
Q

functions of homopolysaccharides and heteropolysaccharides

A

homo: energy storage and structure
hetero: structure and cellular functions

37
Q

starch description and types

A

storage in plants
amylose - unbranched glucose alpha1–>4 glycosidic bonds
amylopectin - branched glucose, alpha1–>4 glycosidic bonds and branches alpha1–>6 every 24-30 residues
amylopectin can be up to 200 million Da

38
Q

glycogen description

A

branched glucose homopolysaccharide storage in animals
alpha1–>4 linear and alpha1–>6 branches every 8-12 residues
7% of the liver by weight

39
Q

solubility of glycogen and starch

A

insoluble due to high molecular weight and form granules
granules contain enzymes for quick breakdown and formation at non reducing ends

40
Q

cellulose

A

insoluble unbranched glucose homopolysaccharide
beta1–>4 linkages
H bonds form between chains excluding water from H bonding

41
Q

who can hydrolyze cellulose bonds?

A

fungi, bacteria and protozoa can hydrolyze beta1–>4 linkages so they can use wood as source of energy
symbiotic organisms in the gut of ruminants and termites

42
Q

what is chitin

A

N-acetyl modified glucose unbranched homopolysaccharides that form skeleton in insects, spiders and crustaceans

43
Q

example of unbranched heteropolysaccharides

A

bacterial sugar coat - they can change sugar coat to hide from the immune system
only 2 monomers used

44
Q

branched heteropolysaccharides

A

contain 3 or more monomers
glycosylation of proteins - monosaccharides and oligosaccharides are added shortly after synthesis
roles: cell-cell interactions (ex. lectins), stabilize against degradation and role in folding of proteins

45
Q

heteropolysaccharides are mostly associated with

A

proteins and lipids

46
Q

N linked oligosaccharides

A

when sugars are added to protein with consensus sequence it is a N-glycosidic bond
added to proteins with Asn-AA-Serine/Threonine as reassembled oligosaccharide units
added to proteins destined for extracellular side of membrane

47
Q

O linked oligosaccharides

A

added directly onto Serine or Threonine side chain (no consensus sequence)
can be destined for intra or extracellular

Biochemistry I (12 decks)

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