BIOLOGY FORM 4

CHEMICAL COMPOSITION OF THE CELL

CARBOHYDRATES

Organic compounds formed by; carbon hydrogen and oxygen.

Ratio = C:H:O 1:2:1

Example : glucose (C6H12O6)

Glucose

Carbohydrates

Monosaccharides

Glucose

Fructose

Galactose

Disaccharides

Maltose

Sucrose

Lactose

Polysaccharides

Glycogen

Starch

Cellulose

Monosaccharides

Known as:

simple sugar

molecular formula C6H12O6

Reducing sugar :

yes

Solubility in water : dissolve

Taste : sweet

Examples : glucose (grape sugar)

Fructose (in fruits and honey

Galactose (milk sugar)

Disaccharides Known as: complex

sugars ( made up of two

molecules of monosaccharid

es

Molecular formula C12H12O11

Reducing sugar : yes for maltose and

lactose but not for sucrose

Solubility in water

: dissolve

Taste : sweet

Examples : maltose

(malt sugars)

Sucrose (in sugar cane and sugar

beet)Lactose

(milk sugar)

Polysaccharides

Known as:

Molecular formula

(C6H1oO5 )n

Reducing sugar :

Solubility in water

:

Taste :Examples :

Formation and breakdown of

disaccharides and polysaccharides

Disaccharides

1. Condensation reaction : Two monosaccharides joined together to

produce a disaccharidesWater molecules is removed.2. Hydrolytic reaction : Disaccharides split into two monosaccharidesWater molecules is added.

Sucrose

+ +H2O

C6H12O6 C6H12O6 C12H12O11

Glucose fructose sucrose

Maltose + +H2O

C6H12O6 C6H12O6 C12H12O11

Glucose glucose maltose

+ +H2O

C6H12O6 C6H12O6 C12H12O11

Glucose galactose lactose

Lactose

Polysaccharides formation

Many monosaccharide's molecules join together to form large polysaccharides molecules.Condensations reactionProcess called polymerization Forms glycogen (animal) and starch and cellulose in plants.Each has different physical and chemical properties, glucose linked and arranged differently.

Polysaccharides breakdown

Polysaccharides undergoes hydrolysis to form monosaccharidesHeating a starch solution in hydrochloric acids hydrolyse starch to glucose enzymes involved: amylase (starch to maltose), maltase (maltose to glucose)Glycogen hydrolyse to glucose in liver

Assesment

1. Name the element present in carbohydrates. (3m)

2. Name the monosacharides units that are formed when maltose, sucrose, and lactose are hydrolysed. (3m)

3. How are polysaccharides formed from monosaccharides? (4m)

Conclusion What you have learned

today?

That’s AllThank you