1. Carbon and Organic Chemistry

• Key Concept: Carbon is essential to life due to its ability to form stable bonds with many elements, including hydrogen, oxygen, and nitrogen.

• Valence Electrons: Carbon has 4 valence electrons, allowing it to form up to four covalent bonds.

• Carbon Chains:

  • Carbon can form long chains (single, double, or triple bonds) that make up the backbone of organic molecules.

  • Hydrocarbons (molecules made of only carbon and hydrogen) are the simplest organic molecules.

  • The length, branching, and shape of carbon chains lead to molecular diversity.

2. Functional Groups

• Definition: Specific groups of atoms within molecules that are involved in chemical reactions.

  • They determine the properties and functions of molecules.

  • Examples: Hydroxyl (-OH), Carboxyl (-COOH), Amino (-NH2), Phosphate (-PO4).

Diagram of Common Functional Groups:

Amino Group(−NH2)\text{Amino Group} \quad (-NH_2)Amino Group(−NH2​)Carboxyl Group(−COOH)\text{Carboxyl Group} \quad (-COOH)Carboxyl Group(−COOH)

3. Biological Macromolecules

• Four Main Classes: Carbohydrates, Proteins, Nucleic Acids, Lipids.

• Monomers & Polymers: Macromolecules are made of smaller units called monomers, which join to form polymers.

4. Carbohydrates

• Monosaccharides: Simple sugars like glucose (C6H12O6C_6H_{12}O_6C6​H12​O6​) used for energy.

• Disaccharides: Two monosaccharides bonded, such as sucrose (glucose + fructose).

• Polysaccharides:

  • Storage: Starch (plants), Glycogen (animals) – both polymers of glucose used to store energy.

  • Structural: Cellulose (plant cell walls) and chitin (exoskeleton of arthropods).

Diagram: Glucose (monosaccharide) structure.

5. Proteins

• Amino Acids: 20 types, each with a central carbon, amino group, carboxyl group, and unique R group (side chain). The properties of the side chain determine the amino acid's behavior (nonpolar, polar, or charged).

Protein Structure:

• Primary: Sequence of amino acids.

• Secondary: α-helix and β-pleated sheets formed by hydrogen bonding.

• Tertiary: 3D shape due to R group interactions.

• Quaternary: Multiple polypeptide chains forming one functional protein.

Diagram: Structure of a generic amino acid.

6. Nucleic Acids

• Function: Store, transmit, and express genetic information.

• Monomers: Nucleotides (composed of a sugar, phosphate group, and nitrogenous base).

• Types:

  • DNA (deoxyribonucleic acid): Double helix structure; stores genetic information.

  • RNA (ribonucleic acid): Single strand; helps in protein synthesis.

Diagram: DNA double helix structure.

7. Lipids

• Types: Fats, Phospholipids, Steroids.

• Fats: Made of glycerol and fatty acids, used for long-term energy storage.

  • Saturated fats have no double bonds (solid at room temp).

  • Unsaturated fats have one or more double bonds (liquid at room temp).

• Phospholipids: Make up cell membranes, having a hydrophobic tail and hydrophilic head, forming bilayers.

• Steroids: Lipids with four fused carbon rings (e.g., cholesterol, hormones).

Diagram: Structure of a phospholipid and its arrangement in the bilayer.

8. Formation and Breakdown of Macromolecules

• Dehydration Reaction: Joins monomers by removing water (H₂O).

  • Example: A+B→AB+H2OA + B \to AB + H_2OA+B→AB+H2​O

• Hydrolysis: Breaks down polymers by adding water.

  • Example: AB+H2O→A+BAB + H_2O \to A + BAB+H2​O→A+B

Summary of Key Concepts

• Carbon’s versatility allows for the diversity of biological molecules.

• Functional groups determine the chemical behavior of organic molecules.

• Macromolecules are essential for life, providing structure, energy storage, and information transfer.

• Proteins perform a variety of roles due to their complex structures.

• Nucleic acids are the blueprint for life, coding for the synthesis of proteins.

• Lipids form cell membranes and store energy efficiently.