Biochemistry Midterm 2.4 - Carbohydrates

Question 1

glycome and glycode

Answer 1

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

Question 2

glycan

Answer 2

polysaccharides made up of monosaccharides linked by glycosidic bonds

Question 3

aldose vs ketose

Answer 3

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

Question 4

oligosaccharides

Answer 4

3-10 monomers long
linked onto lipids and proteins

Question 5

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

Answer 5

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

Question 6

basic monosaccharide nomenclature

Answer 6

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

Question 7

D vs L enantiomers

Answer 7

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

Question 8

number of stereoisomers formula

Answer 8

2^n
n = # of chiral centers

Question 9

epimer definition
equation for # of epimers

Answer 9

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

Question 10

diastereomers

Answer 10

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

Question 11

constitutional isomer’
stereoisomer

Answer 11

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

Question 12

4 carbons D-aldoses diastereomers

Answer 12

D-erythrose
D-threose

Question 13

5 carbon D-aldoses stereoisomers

Answer 13

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

Question 14

six carbon D-aldoses stereoisomers

Answer 14

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

Question 15

3 carbon D-ketose

Answer 15

dihydroxyacetone
no chiral center

Question 16

4 carbon D-ketose

Answer 16

D-Erythrulose

Question 17

5-carbon D-ketoses

Answer 17

D-Ribulose
D-Xylulose
epimers

Question 18

6 carbon D-ketoses

Answer 18

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

Question 19

how hemiacetals and hemiketals are formed and what happens

Answer 19

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

Question 20

pyranose
furanose

Answer 20

pyranose: sugar with 6 membered ring
more stable than furanose

furanose: sugar with 5 membered ring

Question 21

alpha vs beta

Answer 21

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

Question 22

anomeric carbon

Answer 22

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

Question 23

mutarotation

Answer 23

conversion between alpha and beta anomers

Question 24

chair conformations

Answer 24

preferred by pyranoses
requires energy to change conformation

Question 25

change of conformation vs configuration

Answer 25

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

Question 26

how to recognize fructose vs. ribose?

Answer 26

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'

Question 27

glycoside definition

Answer 27

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

Question 28

Glucose fischer structure

Answer 28

Question 29

definition of a free anomeric carbon

Answer 29

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

Question 30

types of tests to check for reducing ends

Answer 30

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

Question 31

acetal/ketal are

Answer 31

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

Question 32

naming disaccharides

Answer 32

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"

Question 33

common names for disaccharides

Answer 33

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

Question 34

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

Answer 34

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)

Question 35

chemical modifications of monosaccharides

Answer 35

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

Question 36

functions of homopolysaccharides and heteropolysaccharides

Answer 36

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

Question 37

starch description and types

Answer 37

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

Question 38

glycogen description

Answer 38

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

Question 39

solubility of glycogen and starch

Answer 39

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

Question 40

cellulose

Answer 40

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

Question 41

who can hydrolyze cellulose bonds?

Answer 41

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

Question 42

what is chitin

Answer 42

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

Question 43

example of unbranched heteropolysaccharides

Answer 43

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

Question 44

branched heteropolysaccharides

Answer 44

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

Question 45

heteropolysaccharides are mostly associated with

Answer 45

proteins and lipids

Question 46

N linked oligosaccharides

Answer 46

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

Question 47

O linked oligosaccharides

Answer 47

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