BCH 203 Chemistry of Carbohydrates

Question 1

Carbohydrates are polyhydroxyl True/False

Answer 1

TRUE

Question 2

Definition of carbohydrate

Answer 2

Carbohydrates are polyhydroxyl alcohols with potentially active carbonyl groups.

Which may be either aldehyde or ketone group. They also contain those compounds which yield them to hydrolysis

Question 3

What are the functions of carbohydrates? And examples

Answer 3

1. Source of energy for living things e.g glucose and fructose
2. It is a storage form of energy e.g glycogen in animals and starch in plants
3. It serves as a structural component e.g cellulose in plants, glycosaminoglycans in animals, chitin in insects
4. Non-digestible carbs such as cellulose, Agar, gum and pectin, serve as dietary fibers
   5.It is a constituent of nucleic acid, RNA and DNA
   6.It plays a role in lubrication. cellular intercommunication and immunity
5. Involved in detoxification e.g glucuronic acid

Question 4

What are the classifications of carbohydrates?

Answer 4

1. Monosaccharide
2. Oligosaccharide
3. Polysaccharide

Question 5

Monosaccharides are soluble in water and sweet to taste TRUE/FALSE?

Answer 5

TRUE

Question 6

What is the most common monosaccharide?

Answer 6

d glucose

Question 7

What is an oligosaccharide?

Answer 7

A short chain of monosaccharide units made up of more than 10 units joined together by a glyclosidic bond

Question 8

What is a polysaccharide?

Answer 8

Polymers consisting of 100’s or 1000’s of monosaccharide units, they are also known as glycans

Question 9

A polysaccharide is sweet and insoluble in water TRUE/FALSE

Answer 9

FALSE A polysaccharide is sweetish and sparingly soluble in water

Question 10

List and describe the types of polysaccharides

Answer 10

1. Homopolysaccharides (homoglycans)
   A polysaccharide made up of several units of the same type of monosaccharide
2. Heteropolysaccharides
   (heteroglycans)
   A polysaccharide containing 2 or more different types of monosaccharide units

Question 11

What are the types of isomerism?

Answer 11

1. Ketose-aldose isomerism
2. D and L isomerism
3. Optical isomerism
4. Epimerism
5. Anomerism

Question 12

Examples of Homopolysaccharides

Answer 12

Starch
Dextrins
Glycogen
Inulin
Cellulose

Question 13

Examples of heteropolysccharides in humans

Answer 13

Glycosaminoglycans (mucopolysaccharides)

Heparin
Chondrotin sulfate
Hyaluronic acid
Dermatan sulfate
Keratan sulfate
Blood group polysaccharide

Question 14

What is the fisher projection of glucose?

Answer 14

Straight chain structural formula of glucose

Question 15

What is the Haworth projection of glucose?

Answer 15

Cyclic formula/ring structure

Question 16

How is a hemiacetal bond formed?

Answer 16

In solution, aldehyde group of monosaccharides react with hydroxy group of the same molecule

Question 17

How is a hemiketal group formed?

Answer 17

In solution, ketone group of monosaccharides react with hydroxy group of the same molecule

Question 18

What is the name of the 6 and 5 membered glucose ring formed by a reaction between the aldehyde group of glucose and the alcohol group of C-4 or C-5

Answer 18

6 - Glucopyranose
5 - Glucofuranose

Question 19

Which glucose ring structure is more stable?

Answer 19

Glucopyranose

Question 20

Most stable form of fructose

Answer 20

Fructofuranose

Question 21

Enantiomers

Answer 21

Isomers which are mirror images of each other

Question 22

When equal amounts of D abs L isomers are in a mixture what is it called

Answer 22

Raecemic mixture/ DL mixture
(No optical activity)

Question 23

Chemical properties of monosaccharides

Answer 23

1. Action of strong acids: Furfural formation
2. Action of Alkalis: Enolization
3. Oxidation: Sugar acid formation
4. Reduction: Sugar alcohol formation
5. Action of phenylhydrazine: Osazone formation

Question 24

Epimers and examples

Answer 24

Diasteromers that differ in the configuration of a single asymmetric carbon
E.g
Glucose and galactose
Glucose and mannose