Basic Biochemistry and Synthetic Polymers

1. Proteins

Proteins are vital biological macromolecules formed by chains of amino acids linked by peptide bonds.

(a) Sources and Properties

1. Sources:

   • Animal Sources: Meat, eggs, milk, fish.
   • Plant Sources: Legumes, nuts, soybeans.

2. Properties:

   • Physical Properties:
     • Solubility: Globular proteins (e.g., albumins) are soluble in water; fibrous proteins (e.g., keratin) are insoluble.
     • Denaturation: Proteins lose their structure and function when exposed to heat, acids, or alkalis.
   • Chemical Properties:
     • Hydrolysis: Proteins hydrolyze into amino acids when treated with acids or enzymes.
       • Example: $$\text{Protein} + \text{H}_2\text{O} \xrightarrow{\text{acid/enzyme}} \text{Amino Acids}$$
     • Laboratory Tests:
       • Ninhydrin Test: Turns purple with amino acids.
       • Biuret Test: Produces a violet color with peptide bonds.
       • Millon’s Test: Detects phenolic groups (tyrosine).

(b) Uses of Proteins

1. Biological Functions:
   • Enzymes (catalysts), hormones (e.g., insulin), structural roles (e.g., collagen).
2. Industrial Uses:
   • Production of enzymes for food processing.
   • Biodegradable materials and pharmaceuticals.

2. Amino Acids

Amino acids are organic compounds with both amine ($-NH_2$) and carboxyl ($-COOH$) functional groups.

(a) Nomenclature and Structure

• General structure: $$\text{R-CH(NH}_2\text{)-COOH}$$
  • R group determines the specific amino acid.

(b) Difunctional Nature

• Amino acids act as both acids (donating $H^+$) and bases (accepting $H^+$), making them amphoteric.

3. Fats and Oils

Fats and oils are triglycerides, consisting of glycerol and three fatty acids.

(a) Sources and Properties

1. Sources:

   • Animal Sources: Butter, lard.
   • Plant Sources: Olive oil, palm oil, coconut oil.

2. Properties:

   • Physical: Oils are liquid at room temperature; fats are solid.
   • Chemical:
     • Hydrolysis: Produces glycerol and fatty acids.
     • Hydrogenation: Converts unsaturated fats into saturated fats.

(b) General Structure

• General formula: $$\text{RCOO-CH}_2\text{-CH(OOCR')-CH}_2\text{OOCR''}$$ Where R, R’, and R’’ are hydrocarbon chains.

(c) Preparation of Soap

Saponification: Fats or oils react with alkali to produce soap and glycerol.

(d) Uses of Fats and Oils

1. Nutritional: Provide energy and essential fatty acids.
2. Industrial: Used in making soap, lubricants, and biodiesel.

4. Carbohydrates

Carbohydrates are organic compounds with the general formula $C_x(H_2O)_y$, serving as energy sources and structural components.

(a) Sources and Nomenclature

1. Sources: Fruits, grains, vegetables, honey.
2. Classification:
   • Monosaccharides: Glucose, fructose.
   • Disaccharides: Sucrose, maltose.
   • Polysaccharides: Starch, cellulose.

(b) Properties

1. Physical:
   • Solubility: Monosaccharides are soluble in water; polysaccharides are insoluble.
2. Chemical:
   • Hydrolysis:
     • Disaccharides → Monosaccharides.
       Example: $$\text{C}_{12}\text{H}_{22}\text{O}_{11} + \text{H}_2\text{O} \xrightarrow{\text{acid/enzyme}} \text{2C}_6\text{H}_{12}\text{O}_6$$
   • Tests:
     • Fehling’s or Benedict’s solution turns red with reducing sugars.

(c) Carbohydrates as Polymers

• Starch: A polymer of glucose, consisting of amylose and amylopectin.
• Formed via condensation polymerization of monosaccharides.

(d) Uses

1. Energy Source: Glucose is the primary energy source for cells.
2. Industrial: Production of ethanol, sweeteners, and paper.

5. Synthetic Polymers

Synthetic polymers are man-made macromolecules formed by polymerizing monomers.

(a) Definition and Types

1. Monomer: A small repeating unit.
2. Polymer: A macromolecule formed by polymerizing monomers.
3. Polymerization Types:
   • Addition Polymerization: Involves unsaturated monomers (e.g., polyethylene).
   • Condensation Polymerization: Involves elimination of small molecules (e.g., nylon, polyester).

(b) Properties of Polymers

1. Thermoplastics: Soften on heating and can be reshaped (e.g., PVC).
2. Thermosetting Plastics: Harden permanently on heating (e.g., Bakelite).

(c) Uses of Polymers

1. Plastics: Packaging, containers, and piping.
2. Resins: Adhesives and coatings.
3. Synthetic Fibers: Nylon and polyester for textiles.

(d) Tests on Plastics

1. Heat Test: Thermoplastics melt; thermosets do not.
2. Acid and Alkali Tests: Evaluate resistance to chemical degradation.

Summary and Applications

• Biochemical Compounds: Provide structural, energy, and functional roles in living systems.
• Synthetic Polymers: Have diverse industrial and domestic applications, replacing natural materials.
  Key Concepts: Understanding polymerization and biochemical structures enables advancements in materials science and biotechnology.