DNA Structure and Nucleotides

Study Notes

Nucleotides are the fundamental building blocks, consisting of deoxyribose sugar, a phosphate group, and one of four nitrogenous bases: adenine (A), thymine (T), cytosine (C), or guanine (G).
DNA has a double helix structure, featuring two strands of nucleotides running in opposite directions, coiling around each other.
Base pairing rules dictate that adenine pairs with thymine, and cytosine pairs with guanine, stabilized by hydrogen bonds.

Information Storage: DNA houses genetic information that governs the characteristics and functions of organisms.
Transcription and Translation: Genetic instructions in DNA are transcribed into RNA and translated into proteins, which manage cellular activities.
Replication: DNA is capable of self-replication, essential for cell division and growth.
Inheritance: Genetic material is passed down from generation to generation, determining traits inherited by offspring.

Nucleotides comprise ribose sugar, a phosphate group, and one of four bases: adenine (A), uracil (U, replacing thymine in DNA), cytosine (C), or guanine (G).
RNA is usually single-stranded but can fold into secondary structures.
In RNA, adenine pairs with uracil, while cytosine pairs with guanine.

Proteins are composed of amino acids which have an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom (-H), and a side chain (R group) that varies among different amino acids.
Peptide Bonds: Amino acids join via peptide bonds to form polypeptide chains.

Primary Structure: The linear sequence of amino acids in a polypeptide chain.
Secondary Structure: Local folding into alpha-helices and beta-sheets, maintained by hydrogen bonds between amino acids.
Tertiary Structure: The 3D configuration of a single polypeptide determined by interactions among R groups.
Quaternary Structure: The arrangement of multiple polypeptide chains (subunits) into a functional protein, involving interactions among side chains, hydrogen bonds, and disulfide bonds.