lecture 2-monoscharides

Question 1

• what is the only sugar that is natrually in L config?

Answer 1

rhamnose and arrabinose

Question 2

• whats special about deoxy sugars like deoxyribose?

Answer 2

missing one or more OH groups

Question 3

• 4. Show the interrelationships of D-glucose, and D-fructose via isomerization

Answer 3

isomerization converts glucose into fructose which has a higher sweetening power. A common process is he conversion of glucose to fructose to make high fructose corn syrup. This process involves the interconversion of D-glucose, D-Mannose, and D-fructose.

glucose→ trans-enediol→ d-fructose→  cis-enediol→ d-mannose

Question 4

• Describe the relationship of sugars to humectancy, water activity and
  microbial inhibition

Answer 4

1. humectancy: have a high affinity to water, making them good at absorbing and holding on to water, as well they are hydrophilic allowing them also to imporve moisture retention
   
   2. water activity: have lower water activity since they bind to water molecules which lessens the amount of free water available
   3. microbial inhibition: since bacteria and microgranisms need a certain level of water activty to thrive and sugars absorb and bind to water making it inactive for bacteria to thrive

Question 5

define chiral and chrial carbon

Answer 5

chiral: mirror images that are non-superimpossible
chiral carbon: 4 different atoms attached to one carbon atom

Question 6

what are the two conditions that must be met to be a sugar?

Answer 6

1. need a ketone or aldehyde
2. there is more than 1 OH (polyhydroxide)

Question 7

define constitional isomers vs stereoisomers

Answer 7

1. same molecular formula but different name like gluclose and fructose
2. sxame molecular formula and same name but diffreent structure (glucose and galactose `

Question 8

aldose vs ketose

Answer 8

aldose: derivide from aldose and suffixe is ose, has 2n config
ketose: dervived from ketone , suffix ulose , fewer config since less chiral centers

Question 9

difference between d and L

Answer 9

D: OH on the greatest carbon is on the right
L: on the left, not digested and not normally natrually occuring

Question 10

pyronose vs furanose

Answer 10

p: more stable 6- membered ring
f- 5 ring

Question 11

axial vs equatioral stability

Answer 11

axial is less stable compared to OH on equatorial positions

Question 12

anomers and anomeric carbon

Answer 12

a pair of almost identical stereoisomers that differ at anomeric carbon (carbon that has carbonul group and during hemiceatal formatio becomes chiral)

Question 13

fischer projection

Answer 13

• vertical
  -top to bottom
  -aldehyde at top
  -primary alchol at bottom

Question 14

romanoff projections

Answer 14

• shows only c-c or c-oh
  -circle=aldehyle
  horizontal lines=loh
  -bottom of vertical line=terminal nonchiral hydroxymethyl

Question 15

haworth projection

Answer 15

-rxn between carbonyl and free electrons and OH group
-for D sugars OH above on 1 is brts nd below on 1 is alpha
- OH left on fischer=up
-OH right on fischer=down
-CH2 OH group on carbon 5 up= D and down for L