Carbohydrates are polyhydroxy aldehydes or ketones, or compounds that produce them on hydrolysis. The term sugar is applied to carbohydrates soluble in water and sweet to taste. Carbohydrates are the major dietary energy sources, besides their involvement in cell structure and various other functions.
Carbohydrates are broadly classified into 3 groups—monosaccharides, oligosaccharides, and polysaccharides. The monosaccharides are further divided into different categories based on the presence of functional groups (aldoses or ketoses) and the number of carbon atoms (trioses, tetroses, pentoses, hexoses, and heptoses).
Functions of carbohydrates
Carbohydrates participate in a wide range of functions
1. They are the most abundant dietary source of energy (4Cal/g) for all organisms.
2. Carbohydrates are precursors for many organic compounds (fats, amino acids).
3. Carbohydrates (as glycoproteins and glycolipids) participate in the structure of cell membrane and cellular functions such as cell growth, adhesion, and fertilization.
4. They are structural components of many organisms. These include the fiber (cellulose) of plants, the exoskeleton of some insects, and the cell wall of microorganisms.
5. Carbohydrates also serve as the storage form of energy (glycogen) to meet the immediate energy demands of the body.
If two monosaccharides differ from each other in their configuration around a single specific carbon (other than anomeric) atom, they are referred to as epimers to each other.
Enantiomers are a special type of stereoisomers that are mirror images of each other.
The process of shifting a hydrogen atom from one carbon atom to another to produce enediols is known as tautomerization.
Mutarotation is defined as the change in the specific optical rotation representing the interconversion of α and β forms of D-glucose to an equilibrium mixture.
- Name a non-reducing disaccharide ___________________________.
2. The carbohydrate that is taken as a reference for writing the configuration of others ____________.
3. If two monosaccharides differ in configuration around a single carbon atom, they are known as ___________________.
4. The α and β cyclic forms of D-glucose are referred to as__________.
5. The noncarbohydrate moiety found in glycosides is known as__________.
6. Give an example of a glycoside antibiotic______________________.
7. The glycosidic bonds at the branching points in the structure of starch are________________.
Answer: α-1,6-Glycosidic bond
8. The polysaccharide employed for the assessment of kidney function_____________________.
9. The glycosaminoglycan that serves as a lubricant and shock absorbent of joints ___________.
Answer: Hyaluronic acid
10. Name the sialic acid, mostly found in the structure of glycoproteins and glycolipids _______.
Answer: N-Acetylneuraminic acid
11. Ribose and deoxyribose differ in the structure around a single carbon, namely
12. One of the following is not an aldose.
13. The glycosaminoglycan that serves as an anticoagulant
(b) Hyaluronic acid
(c) Chondroitin sulfate
(d) Dermatan sulfate.
14. The following polysaccharide is composed of β-glycosidic bonds
15. The carbon atoms involved in the osazone formation
(a) 1 and 2
(b) 2 and 3
(c) 3 and 4
(d) 5 and 6.
- Carbohydrates MCQs
- The Function of Lipids & Phospholipids
- Lipids MCQs with answers
- Amino acids-Definition, Classification, Properties, and Mnemonic codes