Unit 2: Macromolecules & Cell Components

Organic Compounds

Organic compounds are the foundation of biological molecules and are primarily composed of carbon atoms bonded to other elements. Their unique properties allow for the complexity and diversity of life.

• Definition: Organic compounds are molecules that contain carbon atoms bonded to hydrogen and often other elements such as oxygen, nitrogen, sulfur, and phosphorus.

• Valence of Carbon: Carbon has four valence electrons, allowing it to form up to four covalent bonds, resulting in a variety of stable structures including chains and rings.

• CHO: All macromolecules include at least carbon (C), hydrogen (H), and oxygen (O).

• Hydrocarbons: Molecules composed only of carbon and hydrogen (e.g., methane, CH4).

• Importance: Hydrocarbons are rare in living organisms but are important as energy sources (e.g., petroleum).

Carbon Chains and Isomerism

Carbon chains form the backbone of most organic molecules, and their structure can vary in length, branching, and ring formation. Isomerism adds further diversity to organic molecules.

• Chain Length: Carbon skeletons can vary in length, affecting the properties of the molecule.

• Branching: Chains may be unbranched (straight) or branched.

• Double Bonds: Carbon skeletons may have double bonds, which can change the molecule's shape and reactivity.

• Rings: Some carbon skeletons form rings, as seen in many biological molecules.

• Isomers: Compounds with the same molecular formula but different arrangements of atoms. Types include:

  • Structural isomers: Differ in the covalent arrangement of atoms (e.g., butane and isobutane, both C4H10).

  • Cis-trans isomers: Differ in spatial arrangement around double bonds.

  • Enantiomers: Mirror-image isomers, important in biology due to their different biological activities.

• Example: Testosterone and estradiol are both steroids with similar structures but different functional groups, leading to different biological effects.

Chemical Groups (Functional Groups)

Certain groups of atoms, known as functional groups, are key to the chemical behavior of organic molecules. They often participate in chemical reactions and determine the properties of molecules.

• Functional Groups: Groups of atoms that confer specific chemical properties to molecules.

• Polarity: Most functional groups are polar, making molecules hydrophilic (water-soluble).

• Common Functional Groups:

  • Hydroxyl (-OH): Alcohols; increases solubility in water.

  • Carbonyl (C=O): Found in aldehydes and ketones.

  • Carboxyl (-COOH): Acts as an acid; found in amino acids and fatty acids.

  • Amino (-NH2): Acts as a base; found in amino acids.

  • Sulfhydryl (-SH): Found in some amino acids; forms disulfide bonds in proteins.

  • Phosphate (-PO4): Important in energy transfer (e.g., ATP).

  • Methyl (-CH3): Nonpolar and nonreactive; affects gene expression.

• Example: The presence of a hydroxyl group makes ethanol soluble in water.

Macromolecules

Macromolecules are large, complex molecules essential for life. They are built from smaller units called monomers, which are linked together to form polymers.

• Four Major Types:

  • Carbohydrates: Energy storage and structural support (e.g., starch, cellulose).

  • Lipids: Energy storage, membrane structure, signaling (e.g., fats, phospholipids, steroids).

  • Proteins: Catalysis, structure, transport, signaling (e.g., enzymes, antibodies).

  • Nucleic Acids: Information storage and transfer (e.g., DNA, RNA).

• Polymerization: Macromolecules are formed by joining monomers through dehydration synthesis (removal of water).

• Depolymerization: Polymers are broken down into monomers by hydrolysis (addition of water).

• Example: Proteins are polymers of amino acids; starch is a polymer of glucose.

Additional info: The notes above are based on the provided slides and expanded with standard academic context for clarity and completeness.