Biology Course Notes

Biological Molecules Overview

Key Concepts

  • Monomers: Basic units that join to form larger structures (polymers).

    • Examples:

    • Monosaccharides (e.g., glucose).

    • Amino acids (building blocks of proteins).

    • Nucleotides (building blocks of nucleic acids).

  • Polymers: Long chains formed by many repeating monomers.

Types of Biological Molecules

  1. Carbohydrates:

    • Function: Energy storage and structural support.

  2. Proteins:

    • Function: Catalyzing reactions (enzymes).

  3. Nucleic Acids:

    • Function: Store and transmit genetic information.

  4. Lipids:

    • Function: Provide energy and structural functions in cell membranes.

Carbohydrates

Monosaccharides and Disaccharides

  • Monosaccharides:

    • Simplest form: e.g., glucose, fructose.

  • Disaccharides:

    • Formed by condensation reactions:

    • Example: Sucrose (glucose + fructose).

    • Joined by glycosidic bonds.

Storage Forms

  • Starch:

    • Energy storage in plants (iodine test).

  • Glycogen:

    • Energy storage in animals, highly branched for quick release.

  • Cellulose:

    • Structural component in plant cell walls, not digestible by humans.

Testing for Sugars

Reducing and Non-Reducing Sugars

  • Testing Method:

    • Heat sample with Benedict's reagent.

    • Color change indicates presence of reducing sugar (blue to green/orange/brick red).

    • Non-reducing sugars require heating with dilute hydrochloric acid followed by neutralization.

Meaning of Key Terms

  • Condensation Reaction:

    • Joins two monomers; water is released.

  • Hydrolysis Reaction:

    • Breaks bonds between monomers; water is consumed.

Amino Acids and Proteins

Structure of Amino Acids

  • All contain an amino group, a carboxyl group, a variable R group.

  • The 20 common amino acids are categorized into essential and non-essential amino acids.

Formation of Proteins

  • Amino acids join via condensation reactions to form dipeptides and polypeptides.

  • Peptide bonds link amino acids together.

Lipids

Structure and Function

  • Not true polymers; made from fatty acids and glycerol.

  • Types include triglycerides and phospholipids.

    • Triglycerides:

    • Composed of three fatty acids and one glycerol.

    • Energy storage.

    • Phospholipids:

    • Composed of two fatty acids, glycerol, and a phosphate group.

    • Key components of cell membranes (amphipathic nature).

Laboratory Tests and Procedures

Testing for Lipids

  • Emulsion Test:

    • Crush sample, add ethanol, then water; a milky emulsion indicates presence of lipids.

Chemical Reactions

  • Describe key reactions for polymer formation:

    • Condensation Reaction: Forms polymers from monomers while releasing water.

    • Hydrolysis Reaction: Breaks polymers back into monomers using water