AP BIO UNIT 1 (2020-2025)

Structure of nucleotides

Nucleotides have 3’ (HYDROXYL) and 5’ (PHOSPHATE) ends to their sugars, and, during RNA and DNA synthesis, nucleotides are added to the 3’ STRAND only, resulting in a COVALENT bond between nucleotides

Structure of DNA

Antiparallel double helix, 5’ to 3’. Adenine (A) to thymine (T) with TWO hydrogen bonds. Cytosine (C) with guanine (G) with THREE hydrogen bonds.

Structure of proteins

Linear chains of amino acids connected by COVALENT BONDS at the CARBOXYL TERMINUS of the PEPTIDE CHAIN. Primary, secondary, tertiary, and quaternary structures determine protein function

Protein primary structure

Sequence order of amino acids

Protein secondary structure

Local folding of amino acid chains (beta-pleated sheets and alpha helices)

Protein tertiary structure

Overall 3D shape of the protein that often minimizes free energy. Interactions like HYDROGEN BONDS (WEAK), IONIC BONDS (STRONG), DISULFIDE LINKAGES, and HYDROPHOBIC INTERACTIONS between R GROUPS contribute to polypeptide folding. Most enzymes are of tertiary configuration

Protein quaternary structure

Interactions between multiple polypeptide units. ex. Insulin is composed of multiple polypeptide chains linked into globular shape by h-bonds and disulfide linkages

Structure of carbohydrates

Linear chains of sugar monomers connected by COVALENT BONDS. May be linear or branched

DNA and RNA similarities

• Three components (sugar, phosphate group, nitrogenous base) - Form nucleotide units connected by COVALENT BONDS to form linear molecule w/ 3’ and 5’ ends - Nitrogenous bases PERPENDICULAR to sugar-phosphate backbone

DNA and RNA differences

DNA: deoxyribose, thymine, antiparallel double strand; RNA: ribose, uracil, single-stranded