Biological Molecules and Functional Groups

Hydrocarbons are rarely found alone; they often serve as a backbone for functional groups.
Functional groups are small molecules involved in chemical reactions of living systems.
Important functional groups to know:
- Hydroxyl (-OH): found in alcohols; mixes well with water.
- Carbonyl (C=O): forms aldehydes (end of carbon chain) and ketones (middle of carbon chain).
- Carboxyl (-COOH): combines hydroxyl and carbonyl; known as carboxylic acids, releases H+ ions.
- Amino (-NH2): compounds called amines; acts as a base.
- Sulfhydryl (-SH): thiols that form cross-links in proteins, influencing hair structure.
- Phosphate (-OPO3): organic phosphates crucial for DNA backbone and ATP energy storage.
- Methyl (-CH3): affects gene expression, relates to epigenetics.

Macromolecules are large molecules formed from carbon skeletons and functional groups.
Four main types of macromolecules:
- Carbohydrates: provide energy and structural support (e.g., cellulose).
- Proteins: comprise complex structures with varied functions; consist of amino acids.
- Lipids: hydrophobic molecules that include fats, membranes, and hormones.
- Nucleic Acids: DNA and RNA responsible for genetic information storage and processing.

Also called saccharides; consist of carbon, hydrogen, and oxygen in ring structures.
Monomer: monosaccharide; polymer: polysaccharide; linked by glycosidic bonds.
Glucose is a crucial monosaccharide utilized for energy in cell respiration.
Glucose forms:
- Starch: a branching polysaccharide for energy storage in plants.
- Cellulose: a straight polysaccharide that provides structural support in plants.

Composed of branching chains that include nitrogen.
Monomer: amino acid; polymer: polypeptide; linked by peptide bonds.
Proteins serve hundreds of functions and make up most cell structures.
There are 20 different amino acids, each having unique roles in biological processes.

Characterized by hydrophobic properties; lack consistent structure and don’t have monomers or polymers.
Three main types of lipids:
- Steroids (e.g., testosterone, estrogen, cholesterol): four fused rings structure.
- Fats: consist of glycerol and three fatty acids; function mainly in energy storage.
- Phospholipids: composed of phosphate, glycerol, and two fatty acids; essential for cell membranes.
Lipids are linked by ester bonds through dehydration synthesis.