BIOL 150 Lecture 4 (1-26)

Overview of Organic Chemistry

• Organic chemistry studies carbon-containing compounds, focusing on their structures, synthesis, and reactions.
• Organic molecules, primarily hydrocarbons, feature carbon atoms bonded to hydrogen and other elements.

Functional Groups

• Functional groups are specific atom arrangements that grant molecules characteristic properties.
• Major functional groups in biological molecules include:
  • Hydroxyl (-OH)
  • Methyl (-CH3)
  • Carboxyl (-COOH)
  • Carbonyl (C=O)
  • Amino (-NH2)
  • Phosphate (-PO4)

Methyl Group

• The methyl group is the smallest hydrocarbon functional group (-CH3).
• Methylation plays a role in regulating gene expression, protein function, and RNA metabolism.

Hydroxyl Group

• The hydroxyl group (-OH) is present in alcohols, phenols, and carboxylic acids.
• Common in biological molecules, found in carbohydrates, amino acids, and nucleic acids.
• Ethanol (EtOH) is an example of a molecule containing a hydroxyl group.

Carbonyl Group

• The carbonyl group features a carbon atom double-bonded to an oxygen atom (C=O).
• Exists in two varieties: at the end (aldehyde) or in the middle (ketone) of a carbon chain.

Carboxyl Group

• The carboxyl group (-COOH) consists of a carbon atom double-bonded to an oxygen atom and bonded to a hydroxyl group.
• Present in carboxylic acids and amino acids.

Amino Group

• The amino group (-NH2) consists of nitrogen bonded to two hydrogen atoms.
• Found in all amines and amino acids, it provides bonding opportunities due to the presence of a lone electron.

Sulfhydryl Group

• Comprises a sulfur atom bonded to a hydrogen atom (-SH).
• Known as a thiol group, this functional group is important in biological systems.

Polysaccharides

• Complex carbohydrates made of monosaccharide chains linked by glycosidic bonds.
• Ideal for energy storage, large and insoluble, and fold into compact shapes.

Types of Polysaccharides

• Glycogen: A branched polysaccharide stored in animals’ liver and muscles; it serves as the main carbohydrate reservoir for glucose.
• Cellulose: The most abundant organic compound, crucial for plant structure; it is fully permeable to water and solutes.
• Chitin: An unbranched polysaccharide found in arthropod cuticles and fungal cell walls, similar to cellulose.

Phosphate Group

• Part of nucleotides (-PO4); critical for energy transfer in cells (ATP).
• Regulates protein function depending on its presence or absence.

Monomers and Polymers

• Oligomers consist of fewer than 50 monomers linked together.
• Condensation reactions join substances with the loss of a water molecule.
• Hydrolysis reactions involve water being added, resulting in decomposition.

Classes of Organic Molecules

• Four major classes include:
  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic Acids

Carbohydrates

• Composed of carbon and water in the ratio of one carbon to one water molecule (CH2O)n, often referred to as saccharides.
• Types include:
  • Monosaccharides (e.g., glucose, fructose): Single sugar molecules.
  • Disaccharides (e.g., lactose, sucrose): Formed from two monosaccharides.
  • Polysaccharides: Composed of multiple sugars, which can be similar or diverse.

Families of Carbohydrates

• Aldoses: Have a carbonyl at the end of the carbon chain.
• Ketoses: Have a carbonyl within the chain, commonly as 2-ketoses.

Starch vs Cellulose

• Starch is digestible due to alpha glycosidic linkages.
• Cellulose has beta glycosidic linkages, making it indigestible for humans due to a lack of suitable enzymes.