1.4 - Properties of Biological Macromolecules

Polymers and Monomers

• Polymers: Many large biological molecules are polymers, long chains built from smaller repeating units called monomers.

• Monomers: The specific type of monomer used determines the unique properties and functions of each macromolecule.

Carbohydrates

• Monosaccharides: The building blocks of carbohydrates are simple sugars called monosaccharides (e.g., glucose, fructose). These sugars are often used for immediate energy.

• Disaccharides: Two monosaccharides joined by a glycosidic linkage form a disaccharide (e.g., sucrose, lactose, maltose).

• Polysaccharides: Complex carbohydrates are long chains of monosaccharides, forming structures like starch for energy storage or cellulose for structural support in plants.

Proteins

Amino Acids: The monomers of proteins are amino acids, with 20 different types each having a unique R-group (side chain) that determines its properties:

1. Nonpolar (hydrophobic): Avoid water

2. Polar (hydrophilic): Interact with water

3. Charged (acidic or basic): Strongly interact with water

• Peptide Bonds: Amino acids link together by peptide bonds, forming long chains called polypeptides.

• Protein Structure and Function: The sequence of amino acids in a polypeptide determines the protein's unique 3D shape, which is crucial for its specific function (e.g., enzymes, structural proteins, transport proteins).

Key Point: The specific sequence of monomers in a polymer determines its unique properties and functions. Changes in this sequence can have significant biological consequences.

Lipids

• Lipids: Nonpolar, hydrophobic molecules that don't mix well with water.

• Fats: Primarily for energy storage, composed of glycerol and fatty acids:

  • Unsaturated: Have double bonds in fatty acid tails, causing kinks and making them liquid at room temperature.

  • Saturated: Have only single bonds in fatty acid tails, allowing them to pack tightly and be solid at room temperature.

• Phospholipids: Major component of cell membranes, with a polar (hydrophilic) head and nonpolar (hydrophobic) tails.

• Steroids: Lipids with a ring structure, such as cholesterol and hormones.

Nucleic Acids

• Nucleotides: The monomers of nucleic acids, each consisting of:

  • 5-carbon sugar: Deoxyribose (DNA) or ribose (RNA)

  • Phosphate group

  • Nitrogenous base: Adenine (A), guanine (G), cytosine (C), thymine (T in DNA), or uracil (U in RNA).

• DNA: Stores genetic information, double-stranded helix.

• RNA: Involved in protein synthesis and other cellular functions, single-stranded.