Carbohydrates

Question 1

Carbohydrate modification

Answer 1

Adding sugar molecules to other molecules

Question 2

Enantiomers

Answer 2

Isomers that are mirror images of each other

Question 3

Primary enantiomeric form of monosaccharides in nature

Answer 3

D form

Question 4

Diastereoisomers

Answer 4

Isomers that are not mirror images of each other

Can be epimers or anomers

Question 5

Epimers

Answer 5

Isomers that differ around only 1 chiral center

Question 6

Isomers

Answer 6

Have same molecular formula but different structures

Can be constitutional isomers or stereoisomers

Question 7

Constitutional isomers

Answer 7

Differ in the order of attachment of atoms

Question 8

Stereoisomers

Answer 8

Atoms are connected in the same order but differ in spatial arrangement
Can be enantiomers or diastereoisomers

Question 9

Anomers

Answer 9

Isomers that differ at a new asymmetric carbon atom formed on ring closure

Question 10

Form of which most monosaccharides of chains 5 carbons or longer exist

Answer 10

Rings

Question 11

Alpha vs. beta form of anomers

Answer 11

Alpha- hydroxyl at C1 or C2 is below ring

Beta- hydroxyl at C1 or C2 is above ring

Question 12

Interchangeability of anomers

Answer 12

Anomers can interchange between their two forms without needing an enzyme to catalyze the reaction

Question 13

Reducing sugars

Answer 13

Sugars without O- or N- linkages

Can be readily oxidized

Question 14

Fehling’s solution

Answer 14

Test for reducing sugars: reducing sugars can reduce Cu+2 to Cu+

Question 15

Consequences of phosphorylating sugars

Answer 15

1. Make sugar more reactive

2. Glycolysis: trap glucose in cell (prevents diffusion and transport by transporters)

Question 16

Glycosidic linkages

Answer 16

Linking two sugars together through an ether bond (1 carbon of one ring bonded to an oxygen bonded to a carbon of a different ring)

Question 17

Reducing power of linked sugars

Answer 17

No reducing power- rings are linked together and won’t open up

Question 18

Glycogen linkages

Answer 18

Heavily branched

Many alpha-1,4 and alpha-1,6 sugar linkages

Question 19

Cellulose linkages

Answer 19

All beta-1,4 linkages
Oxygens in glycosidic bonds alternate between being above the rings and below the rings
Gives structural rigidity

Question 20

Reason why cellulose can’t be digested

Answer 20

Enzymes don’t recognize beta-1,4 linkages

Question 21

Proteoglycans

Answer 21

Proteins attracted to long repeats of glycosaminoglycans

Mostly sugar with a little protein

Question 22

Function of proteoglycans

Answer 22

Exist at intersection of tissues: cushioning and shock absorption
Negative charges attract water

Question 23

Function of glycosyltransferases

Answer 23

Enzymes that function in linking sugars during sorting in ER and Golgi
Active site of enzyme bind to Asn of protein (if N-linked) or Ser/Thr of protein (if O-linked) and also sugar
Get energy needed for reaction by ATP transferring phosphate

Question 24

Function of UDP in reacting with sugar monomers

Answer 24

Charges monomer: gives it energy to move

Question 25

Sugar linkages in blood type antigens

Answer 25

O antigen lacks sugar attached to Gal in chain

A and B antigens have different versions of sugar attached to Gal in chain

Question 26

Glycoprotein

Answer 26

Proteins with sugar moieties

Mostly protein with a little sugar

Question 27

Erythropoetin (EPO)

Answer 27

Example of glycoprotein
Triggers body to make RBCs when in low O2 environment
Synthetic version (sometimes used by athletes to cheat) has different glycosylation pattern, which can be detected by mass spec

Question 28

Leukocyte rolling

Answer 28

Cells on surface of blood vessel express proteins with sugars attached to them in an attempt to attract WBCs