Disaccharides: Two monosaccharides linked by a Glycosidic Linkage (e.g., Sucrose, Lactose, Maltose).
Structural examples: Cellulose (found in plant cell walls), Chitin (found in fungi cell walls & exoskeleton of arthropods).
Storage examples: Starch (found in plants), Glycogen (found in animals).
Starch vs. Cellulose: Differ in the linkage of glucose monomers. Starch has 1-4 linkage of α glucose monomers, while cellulose has 1-4 linkage of β glucose monomers.
Proteins
Composed of C, H, O, N, & S.
Monomer: Amino Acid.
Bond: Peptide bond (between carboxyl & amino groups).
Structure:
Primary: String of amino acids.
Secondary: Alpha helix or beta pleated sheet, stabilized by hydrogen bonds between the backbones.
Tertiary: Final 3D structure, stabilized by ANY bonds (hydrogen, covalent, ionic, …) between R groups.
Quaternary: Arrangement of multiple polypeptides, stabilized by ANY bonds (hydrogen, covalent, ionic, …) between R groups of different polypeptides.
R groups can be hydrophilic (exterior), hydrophobic (interior), or charged.
Lipids
Composed of C, H, O, & P (in phospholipids).
Monomer: N/A.
All lipids are NONPOLAR.
Fats: Glycerol + 3 fatty acids.
Phospholipids: Phosphate + Glycerol + 2 fatty acids. Amphipathic (have both hydrophilic and hydrophobic regions).
Hydrophilic head (phosphate) attracted to water.
Hydrophobic tail (fatty acids) repelled by water.
Steroids: Four fused rings (e.g., cholesterol).
Saturated fatty acids: ALL single bonds (each carbon is SATURATED by hydrogen).
Unsaturated fatty acids: At least one double bond (not all carbons are SATURATED by hydrogen).