Chapter 4- Carbohydrates

Question 1

What do you call a three carbon sugar? four carbon sugar? Five carbon sugar?

Answer 1

Triose
Tetrose
Pentose
Hexose

Question 2

What do you call a sugar with an aldehyde as their most oxidized group? What do you call a sugar with a key tone as their most oxidized group?

Answer 2

Aldose
Ketose

Ex. aldohexose

Question 3

Carbohydrates can be labeled as D (dextro) or L (levo) which side of the Fischer projection denotes D/L?

Answer 3

Right-D
Left- L

*the sugar with the highest number of Cairo carbon with the OH group on the left or right.

Question 4

D and L forms of the same sugar or what type of stereoisomer?

Answer 4

Enantiomers

Question 5

What do you call the diastereomer that only differs at one chiral center?

Answer 5

Epimer

Question 6

What do you call the epimer that differs at the anomeric carbon?

Answer 6

Anomer

Question 7

How do you classify an alpha/Beta anomer?

Answer 7

Alpha anomers have the OH group on the anomeric carbon trans (opposite) to the free CH20H group.

Beta anomers have the OH group on the anomeric carbon cis (same side) to the free CH20H group.

Question 8

What is mutorotation?

Answer 8

Shifting from one anomeric form to the other with the straight chain form as an intermediate

It happens in the presence of water

Question 9

What are the three main reactions that monosaccharides can undergo?

Answer 9

Oxidation reduction reactions, esterification, and glycoside formation.

Question 10

What to test can be used to test for reducing sugars?

Answer 10

Tollens and Benedict’s reagents

Question 11

What can you add to test for the presence of glucose?

Answer 11

Glucose oxidase. It does not react with other reducing sugars.

Question 12

Briefly describe the process of Esterification.

Answer 12

Combination of a sugar/carbohydrate plus carboxylic acid yields an Ester

Question 13

Describe the process of glycoside formation.

Answer 13

Carbohydrates plus alcohol yields an acetate. The bond formed is called at like acidic bond which is formed between the two hydroxyl groups.

Formation of a glycosidic bond is a hydration reaction. Breaking of a glycosidic bond is a hydrolysis reaction.

Question 14

What are the three common disaccharides?

Answer 14

Sucrose glucose fructose
Lactose-galactose glucose
Mannose-glucose and glucose

Question 15

What are the four sugars you should memorize for the MCAT?

Answer 15

D fructose, D glucose, D galactose, D-mannose

Question 16

What is cellulose?

Answer 16

Polysaccharide that is the main structural component for plant cell walls and a main source of fiber in the human diet.

Question 17

What are the two types of starches and what are their functions?

Answer 17

Amylose and amylopectin. The main energy storage form for plants.

Question 18

What is glycogen and what is its function

Answer 18

Glycogen is a Homie polysaccharide made up of multiple glucose molecules and it functions of the main energy storage for animals.

Question 19

Any hemiacetal/hemiacetal ring is called what?

Answer 19

A reducing sugar because it can be oxidized

Question 20

Oxidation of an aldose results in what?

Answer 20

Lactone

Question 21

Hemiacetals react with alcohols to form what?

Answer 21

Acetals

Question 22

What type of reaction is glycoside formation?

Answer 22

Dehydration reaction

Question 23

What type of reaction is the breaking of a glycosidic bond?

Answer 23

Hydrolysis

Question 24

In order to make a disaccharide or polysaccharide what type of bond is utilized?

Answer 24

Glycosidic bonding between monosaccharides