BIOLOGY FORM 4 CHAPTER 4 - CHEMICAL COMPOSITION OF THE CELL PART 1
4.2 carbohydrates
2. Carbohydrates are an important source of
energy that can be used by the cells.
Carbohydrates contain carbon, hydrogen and
oxygen.
The ratio of hydrogen atoms to oxygen atoms
in one molecule of carbohydrate is 2:1
4. Monosaccharides are monomers of
carbohydrates which are the simplest type of
carbohydrates. (simple sugars)
Main source energy for many cells
Long chain monosaccharides can combine
with proteins and lipids forming glycoprotein
and glycolipids respectively.
Examples: glucose, fructose, galactose
5. Glucose is found in plants and fruits.
Chemical formula for glucose: C6H12O6
Fructose is found in sweet fruits and honey
Glactose is found in milk
Monosaccharides are reducing sugars(act as a
reducing agent)
6. Disaccharide is formed when two
monosaccharides are formed by means of
condensation
Condensation involves the removal of a
water molecule when a bond is formed
between two molecules of monosaccharides
Examples: maltose, sucrose, lactose
7. Maltose is formed from condensation of 2
glucose molecules
Sucrose is formed from glucose and fructose
Lactose is formed from glucose and galactose
Disaccharides can be broken into
monosaccharides by hydrolysis
Hydrolysis is a reaction involving the addition of
water.
8. condensation
Glucose + Glucose Maltose + water
hydrolysis
Maltose is malt sugar
Sucrose is cane sugar
Lactose is milk sugar
Maltose and lactose are reducing sugars
Sucrose is non-reducing sugars
9. Polysaccharides is the combination of
hundreds of monosaccharides through
condensation
Polysaccharides are polymers formed by
condensation of glucose monomers
10. Insoluble in water( due to their large molecular
size)
Do not taste sweet
Do not crystalize
Examples: starch, glycogen, cellulose
Starch is found in plants (wheat, rice, potatoes,
bread and corn)
Starch is the main carbohydrate reserve in plants.
11. Glycogen(animal starch) is the main reserve of
carbohydrates in animals and yeast
Humans and animals store glycogen mainly in liver
and muscle cells
Polysaccharide chain in glycogen are highly
branched
Cell walls of plants are made of cellulose.
12. Polysaccharides
can be broken down into smaller
molecules through hydrolysis by adding diluted acid
or through enzymatic action
hydrolysis
Polysaccharides + Acid Monosaccharides