Nucleic Acids and the RNA World Lecture Notes

This flashcard set covers the biochemical properties of DNA and RNA, the history of their discovery, chemical evolution theories, and the endosymbiotic origins of eukaryotes.

Nucleotide

The basic chemical building block of nucleic acids like DNA an RNA. The monomer that makes up nucleic acids, composed of a phosphate group, a 5-carbon sugar, and a nitrogenous base.

Ribose

The 5-carbon sugar found in RNA that contains an $-OH$ group at the $2'$ carbon.

Deoxyribose

The 5-carbon sugar found in DNA that lacks an oxygen at the $2'$ carbon, making it less reactive than ribose.

Purines

A class of nitrogenous bases characterized by a double-ring structure, which includes Adenine (A) and Guanine (G).

Pyrimidines

A class of nitrogenous bases characterized by a single-ring structure, which includes Cytosine (C), Uracil (U), and Thymine (T).

Sugar phosphate backbone

It provides stability, defines molecular directionality (5' to 3'), and carries negatively charged, hydrophilic groups on the outside of the helix.

Chargaff’s Rules

The observation that the total number of purines equals the total number of pyrimidines, specifically that the amount of $A = T$ and $C = G$.

Antiparallel

The nature of DNA strands where they run in opposite directions, one in the $5' \rightarrow 3'$ direction and the other in the $3' \rightarrow 5'$ direction.

Central Dogma

The framework for information flow in a cell: DNA is used to synthesize mRNA in the nucleus, which then moves to the cytoplasm to guide the synthesis of proteins.

Hairpin

A common secondary structure in RNA formed when a single strand folds back on itself with complementary base pairing, creating a stem and a loop.

Ribozyme

An RNA molecule that exhibits catalytic properties, similar to an enzyme, and is capable of aiding in protein production or self-replication.

Chemical Evolution

The theory that simple molecules on ancient Earth reacted to create larger, more complex organic molecules such as amino acids, sugars, and nitrogenous bases.

The RNA World Hypothesis

The proposal that the first life-form was a naked self-replicator made of RNA, as RNA can provide a template for copying and catalyze its own polymerization.

Stanley Miller’s Experiment

A 1953 experiment that added kinetic energy (spark discharge) to a mix of simple gases ($CH_4$, $NH_3$, $H_2$) and boiling water, resulting in the formation of amino acids.

Surface Metabolism Theory

The theory that minerals found in deep-sea hydrothermal vents catalyzed spontaneous reactions between high-energy molecules to form complex organic compounds like ribose.

Protocell

A simple precursor to a cell, possibly formed from polypeptide globules (proteinoid microspheres) or lipid bilayers that encased catalytic RNA.

Organelle

A membrane-bound compartment specialized for a particular function within a cell, common in eukaryotic cells.

Endosymbiont Theory

The theory that mitochondria and chloroplasts originated as independent prokaryotes that were engulfed by a host cell and became permanent internal components.

RNA

the first self replicating molecule. Surrounded by membrane.

The theory of chemical evolution

Life began as a naked self replicator. Not enclosed in a membrane.

information stored in RNA

Can be used to make copies (base pairing)