1. Carbohydrates

2. Carbohydrates
Carbohydrates are the most abundant organic molecules in nature .
Carbohydrates formula : (CH2O)n
Functions of carbohydrates:
Energy in the diet
Storage form of energy in the body
Cell membrane components
Structural component of many organisms

3. Classification of carbohydrates
Monosaccharides : simple sugars
Disaccharides : contain two monosaccharides
Polysaccharides : contain many monosaccharides
Origin:
Carbohydrates are formed in plants by a process called photosynthesis
Compounds that have same chemical formula but have different structures are called isomers

4. Monosaccharides (Simple sugars)
Aldoses
Ketoses
depending on they contain an aldehyde or a ketone group
Hexoses (six-carbon monosaccharides):
are the most common monosaccharides
Glucose
Fructose
Galactose

5. Glucose : Galactose: Fructose : - Is an aldohexose
- Is commonly Known as dextrose
- Is the most important of all monosaccharides and is normally found in the bloodstream and in the tissue fluids
Galactose:
- Is one of the constituents of lactose
Fructose :
- Is a ketohexose
- Is commonly known as fruit sugar
- Is one of the constituents of sucrose

6. Monosaccharides and its chemical reactions
The hexoses either aldehydes or ketones can act as reducing agents
Hexose + alkaline Cu complex (Fehling s solution or Benedict s solution) →
A red-orange precipitate of Cu2O is formed
This reaction is the basis for the test for sugar in the urine
Hexoses will ferment in the presence of enzymes found in yeast

7. Disaccharides Sucrose :(table sugar) Glucose + Fructose
Maltose :(obtained by the partial hydrolysis of starch)
Glucose + Glucose
Lactose :(sugar in milk)
Glucose + Galactose

8. Disaccharides and its chemical reactions
Of the three disaccharides only maltose and lactose show reducing properties with alkaline Cu complex ions.
Sucrose is not a reducing sugar .
Sucrose and maltose will ferment with yeast due to the presence of the enzymes sucrase and maltase.
Lactose will not ferment with yeast because of the absence of the enzyme lactase be

9. Polysaccharides - Polysaccharides are polymers of monosaccharides
- Hydrolysis of Polysaccharides → monosaccharides
- Three common polysaccharides:
Starch
Cellulose
Glycogen
- Plants store their food as starch
Plants use cellulose as supporting and structural parts
Animals use glycogen as a reserve supply of carbohydrate.

10. Properties of polysaccharides
Polysaccharides have a high molecular mass
Insoluble in water
Tasteless
Give negative tests for reducing sugars
These properties are the opposite of those for monosaccharides and disaccharides

11. A carbohydrate that can be given intravenously is
Cellulose b. Sucrose
Lactose d. Glucose
An example of a disaccharide is
a. Glucose b. Maltose
Cellulose d. Starch
An example of hexose is
a. Sucrose b. lactose
Galactose d. Ribose

12. Animals store carbohydrates in the form of
Cellulose b. Glucose
Starch d. Glycogen
An example of a polysaccharide is
Starch b. Glycogen
Cellulose d. All of these
When sucrose is hydrolyzed, it yields
Glucose only
Glucose and fructose
Glucose and galactose
Ribose and galactose

13. Alkaline Cu complex ions are used to test for the presence of
Aldehydes b. Ketones
Acids d. Oxidizing sugars
An example of a pentose is
Maltose b. talose
Glyceraldehyde d. Ribose