AP Biology: Introduction to Biological Macromolecules

Understanding of biological macromolecules is crucial in AP Biology, particularly in the study of biochemical interactions and systems.
Biological systems exhibit complex properties due to interactions at various levels.

Major biological macromolecules include:
- Carbohydrates
- Lipids
- Proteins
- Nucleic Acids

Macromolecules: Large molecules formed by bonding multiple smaller molecules (monomers) through covalent bonds.

Composition: Made of carbon, hydrogen, and oxygen in a ratio of $1:2:1$ (ex. $C<em>6H</em>{12}O_6$ ).
Functions:
- Main source of energy for living things.
- Structural roles in plants and animals.
Types of Carbohydrates:
- Monosaccharides: Single sugar molecules (e.g. glucose).
- Disaccharides: Two sugar molecules bonded (e.g. sucrose).
- Polysaccharides: Many sugar molecules bonded (e.g. starch, glycogen, cellulose).

Starch: Energy storage in plants.
Glycogen: Energy storage in animals; mainly found in liver and muscle cells.
Cellulose: Structural component of plant cell walls.

Composition: Made of carbon, hydrogen, and oxygen, but not in a fixed ratio.
Characteristics: Generally non-polar, hydrophobic, and insoluble in water.
Types of Lipids:
- Fats: Composed of glycerol and fatty acids (saturated and unsaturated fats).
- Phospholipids: Contain a hydrophilic head and hydrophobic tails, crucial for cell membrane structure.
- Waxes: Provide waterproofing.
Functions: Energy storage, insulation, and forming cell membranes.

Saturated Fats: No carbon-carbon double bonds; solid at room temperature (e.g., butter).
Unsaturated Fats: One or more carbon-carbon double bonds; liquid at room temperature (e.g., olive oil).

Components: Made up of nucleotides containing a sugar, phosphate group, and nitrogenous base (A, T, C, G for DNA; A, U, C, G for RNA).
Functions: Store and transmit genetic information; DNA is double-stranded, whereas RNA is single-stranded with uracil replacing thymine.

Composition: Made of amino acids, containing carbon, hydrogen, oxygen, and nitrogen.
Functions: Serve various roles incl. enzymes, transport, structural support (e.g. flexibly), signaling, immune response.
Structure:
- Primary Structure: Sequence of amino acids.
- Secondary Structure: Hydrogen bonding produces $α$ -helices and $β$ -pleated sheets.
- Tertiary Structure: 3D structure based on interactions between side chains.
- Quaternary Structure: Assembly of multiple polypeptide chains.

Covalent Bonds: Formed through dehydration synthesis; broken with hydrolysis.
- Glycosidic Linkages: Connect carbohydrates.
- Ester Bonds: Connect lipids.
- Peptide Bonds: Connect proteins.
- Phosphodiester Bonds: Connect nucleotides in nucleic acids.

Dehydration Synthesis: Process of joining two monomers by removing a water molecule.
Hydrolysis: Process of breaking down polymers into monomers through the addition of water.

Role of Enzymes: Proteins that catalyze biochemical reactions; speed up reactions without being consumed.
Specificity: Each enzyme is specific to a particular substrate, akin to a “lock and key.”

Nucleic Acids: Directionality influences function; DNA strands are antiparallel.
Proteins: The sequence and characteristics of amino acids determine the final structure and function.

Understanding the structure and function of biological macromolecules is foundational in AP Biology.
The type of bonds and the properties of monomeric units significantly affect the macromolecules' properties and functions, leading to their roles in biological systems.