Recording-2025-03-08T12:06:22.157Z

Micromolecules and Macromolecules

• Micromolecules are essential molecular components that make up most substances.

• Example: Proteins are large molecules composed of hundreds to thousands of smaller units.

Classes of Macromolecules

• Macromolecules are large molecules divided into four classes:

  • Carbohydrates

  • Lipids

  • Proteins

  • Nucleic acids

• Macromolecules are referred to as polymers, formed by linking smaller units called monomers.

  • Example: A string of beads represents a polymer, with each bead symbolizing a monomer.

Monomers and Polymers

• Three classes (carbohydrates, proteins, nucleic acids) are true polymers.

• Lipids are not true polymers.

• Polymers are made by dehydration synthesis, a reaction that joins monomers together while releasing water (dehydration reaction).

• Hydrolysis reaction is the breakdown of polymers into monomers using water.

Digestive Process

• Polymers are too large to be absorbed by the intestines; they must be broken down into smaller monomers.

  • Enzymes play a crucial role in this process:

    • Break down polysaccharides into monosaccharides.

    • Break down proteins into amino acids.

• After digestion, monomers are absorbed into the bloodstream and can be reassembled into larger molecules as needed.

Carbohydrates

• Carbohydrates include sugars and their polymers.

• The simplest form is monosaccharides (e.g., glucose - C6H12O6).

  • Glucose is the most commmon monosaccharide and is the centrral importance in the chemistry of life

    • Glucose is an aldose

• Monosaccharides are classified by:

  • Location of the carbonyl group (aldehyde or ketone).

  • Number of carbons (trioses, pentoses, hexoses).

• Disaccharides are formed by joining two monosaccharides through covalent bonds (e.g., sucrose, lactose, maltose).

Polysaccharides

• Polysaccharides are long chains of monosaccharides, used for energy storage (e.g., starch, glycogen) and structural support (e.g., cellulose).

  • Starch has two forms:

    • Amylose: A linear chain of glucose.

    • Amylopectin: A branched chain of glucose units.

• Cellulose: A major structural component in plant cell walls, composed of beta-glucose which cannot be digested by humans but is digested by microbes in some animals.

Lipids

• Lipids are a diverse group of biological molecules that do not mix with water, characterized by:

  • Hydrophobic nature due to non-polar covalent bonds.

• Main types of lipids include:

  • Fats (glycerol and fatty acids), Phospholipids, and Steroids.

• Fats are formed by linking three fatty acids to glycerol via dehydration reactions; these are called triacylglycerols.

  • Fatty acids can be:

    • Saturated (no double bonds) - typically solid at room temperature (e.g., butter).

    • Unsaturated (one or more double bonds) - typically liquid at room temperature (e.g., oils).

Phospholipids

• Phospholipids have hydrophilic heads and hydrophobic tails, forming lipid bilayers in water, crucial for cell membranes.

• The cell membrane structure is vital for the existence of life.

• This lipid forms he main structural component of cell membranes

Steroids

• Steroids are characterized by a carbon skeleton consisting of four fused rings (e.g., cholesterol).

• Cholesterol is a precursor for important steroids such as testosterone.

SUGARS

• carbonyl group (cooh) that forms ring structure with a hydroxyl group that forms ring structure when the dry molecule is placed in water