Chapter 4 - Carbohydrate Structure and Function

Question 1

Carbohydrate Empirical Formula

Answer 1

Cn(H2O)m

Question 2

aldose

Answer 2

• contain and aldehyde as their most oxidizable group - can participate in glycosidic linkages at C1

Question 3

Ketoses

Answer 3

• contain ketones as their most oxidizable group - participate in glycosidic linkages at C2

Question 4

Glycosidic linkages

Answer 4

• it is a covalent bond that links a carbohydrate to another group, which may or may not be a carbohydrate

Question 5

D- Glucose

Answer 5

Question 6

D-Fructose

Answer 6

Question 7

D- Galactose

Answer 7

Question 8

D- Mannose

Answer 8

Question 9

Optical Isomers

Answer 9

• have the same chemical formula but only differ in spatial arrangement

Question 10

Enantiomers

Answer 10

• moleducules that are not superimposible on each other
• contain a stereogenic center (4 different groups)
• R,R –> S,S

Question 11

Absolute Configuration

Answer 11

this is determined by the groups that are attached around the central carbon

Question 12

How can you calculate the number of stereoisomers?

Answer 12

Number of Stereoisomers = 2ⁿ

^{n = number of chiral centers}

^{(i.e 4 chiral centers will lear to having <strong>16</strong> stereoisomers)}

Question 13

Fisher Projections

Answer 13

• horizontal lines are wedges (out of page)
• verticle lines are dashes (into the page)
• all D sugars have hydroxide on the right
• L have hydroxide on the left

Question 14

Diastereomers

Answer 14

• Have the same number of carbon but are NOT mirror images of one another
• R,R –> R,S

Question 15

Epimers

Answer 15

• all epimers are diastereomers but not all diastereomers are epimers

Question 16

Hawthorn Projection

Answer 16

• 3D depiction of five or six membered sugars
• anyhing on the right of Fischer projections will point down

Question 17

Mutarotation

Answer 17

• spontaneous configuration change about C-1; when exposed to water
• causes mixture of alpha (36%) and beta (64%)
• alpha has the anomeric carbon in the axial position which is unfavorable

Question 18

Aldonic Acids

Answer 18

occur due to opening of cyclic sugar and are aldehyde is oxidized

Question 19

Tollen’s Reagent

Answer 19

• (Ag(NH₃)⁺₂)
  
  • is an oxidizing agent

Question 20

Benedict’s Reagent

Answer 20

• readily oxidized aldehydes in aldoses

Question 21

Tautomerization

Answer 21

is the rearangement of bonds in the compound (carbonyl) and ends with a double bond placed between two carbons bonded to hydroxyl group

Question 22

Sucrose

Answer 22

Question 23

Maltose

Answer 23

Question 24

Lactose

Answer 24

Question 25

Cellulose

Answer 25

• linked by beta-1,4 glycosidic bonds
• cannot be digested by humans due to lacking cellulose enzyme

Question 26

Starches

Answer 26

• plants store starch as amylose; a linear glucose polymer with alpha-1,4 glycosidic linkages
• iodine well known to test for presence of starch
• alpha/beta anylase break down starch to use for energy
  
  • beta cleaves at non-reducing end to yield maltose
    
    • alpha will randomly cleave

Question 27

Glycogen

Answer 27

• carbohydrate storage unit of animals
• similar to starch but contains more alpha 1,6 bonds (1 per 10 glycose)
• highly branching makes it more souluble
  *

Question 28

Glycogen Phosphorylase

Answer 28

this molecules cleaves glycogen from its non-reducing end to make a glucose and then it phosphorilates it