1. Biological Molecules Overview
Importance of Biological Molecules
All life processes depend on biological molecules.
Four main types: carbohydrates, proteins, lipids, and nucleic acids.
Organic molecules contain carbon; they are often polymers made of
monomers.
2. Carbohydrates
Types of Carbohydrates
Monosaccharides: Single sugar units (glucose, fructose, galactose).
o Glucose has two isomers: α-glucose and β-glucose.
o General formula: (CH₂O)ₙ.
Disaccharides: Formed by a condensation reaction between two
monosaccharides, forming a glycosidic bond.
o Examples:
Maltose = glucose + glucose
Sucrose = glucose + fructose
Lactose = glucose + galactose
Polysaccharides: Many monosaccharides linked together (starch,
glycogen, cellulose).
Structure and Function
Starch: Storage polysaccharide in plants (amylose and amylopectin).
o Amylose: Unbranched, helical structure, α-glucose.
o Amylopectin: Branched, α-glucose.
Glycogen: Storage polysaccharide in animals, highly branched, α-glucose.
Cellulose: Structural polysaccharide in plant cell walls, β-glucose, forms
strong fibers (microfibrils).
Testing for Carbohydrates
Benedict’s test (for reducing sugars): Positive result = red/orange
precipitate.
Non-reducing sugars: Hydrolyze with acid, then repeat Benedict’s test.
Iodine test (for starch): Positive result = blue-black color.
3. Lipids
Importance of Biological Molecules
All life processes depend on biological molecules.
Four main types: carbohydrates, proteins, lipids, and nucleic acids.
Organic molecules contain carbon; they are often polymers made of
monomers.
2. Carbohydrates
Types of Carbohydrates
Monosaccharides: Single sugar units (glucose, fructose, galactose).
o Glucose has two isomers: α-glucose and β-glucose.
o General formula: (CH₂O)ₙ.
Disaccharides: Formed by a condensation reaction between two
monosaccharides, forming a glycosidic bond.
o Examples:
Maltose = glucose + glucose
Sucrose = glucose + fructose
Lactose = glucose + galactose
Polysaccharides: Many monosaccharides linked together (starch,
glycogen, cellulose).
Structure and Function
Starch: Storage polysaccharide in plants (amylose and amylopectin).
o Amylose: Unbranched, helical structure, α-glucose.
o Amylopectin: Branched, α-glucose.
Glycogen: Storage polysaccharide in animals, highly branched, α-glucose.
Cellulose: Structural polysaccharide in plant cell walls, β-glucose, forms
strong fibers (microfibrils).
Testing for Carbohydrates
Benedict’s test (for reducing sugars): Positive result = red/orange
precipitate.
Non-reducing sugars: Hydrolyze with acid, then repeat Benedict’s test.
Iodine test (for starch): Positive result = blue-black color.
3. Lipids
