Last universal common ancestorThe last universal common ancestor (LUCA) is the hypothesized latest common ancestral population of single-celled organisms from which all subsequent life forms descend under the three-domain system of Bacteria, Archaea, and Eukarya. Most studies suggest that the LUCA existed by 3.5 billion years ago, and possibly as early as 4.3 billion years ago or earlier. The nature of this point or stage of divergence remains a topic of research.
ProtocellLipid globule proposed as a precursor of living cellsA protocell (or protobiont) is a self-organized, membrane-bound or membraneless compartment that concentrates biomolecules, proposed as a rudimentary precursor to cells during the origin of life. It is a minimal unit that can undergo Darwinian evolution.
Domain (taxonomy)In biological taxonomy, a domain ( or ) (Latin: regio or dominium), also dominion, is the highest taxonomic rank of all organisms taken together. It was introduced in the three-domain system of taxonomy devised by Carl Woese, Otto Kandler and Mark Wheelis in 1990. According to the domain system, the tree of life consists of either three domains, Archaea, Bacteria, and Eukarya, or two domains, Archaea and Bacteria, with Eukarya included in Archaea.
RNA worldThe RNA world is a hypothetical stage in the evolutionary history of life on Earth in which self-replicating RNA molecules proliferated before the evolution of DNA and proteins. The term also refers to the hypothesis that posits the existence of this stage. Alexander Rich first proposed the concept of the RNA world in 1962, and Walter Gilbert coined the term in 1986.
RNAFamily of large biological moleculesA hairpin loop from a pre-mRNA. Highlighted are the nucleobases (green) and the ribose-phosphate backbone (blue). This is a single strand of RNA that folds back upon itself. Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA).
Cell (biology)The cell is the basic structural and functional unit of all forms of life or organisms. The term comes from the Latin word cellula meaning 'small room'. A biological cell basically consists of a semipermeable cell membrane enclosing cytoplasm that contains genetic material. Most cells are only visible under a microscope. Except for highly-differentiated cell types (examples include red blood cells and gametes) most cells are capable of replication, and protein synthesis.
Carl WoeseCarl Richard Woese ( ; July 15, 1928 – December 30, 2012) was an American microbiologist and biophysicist. Woese defined the Archaea (a new domain of life) in 1977 through a pioneering phylogenetictaxonomy of 16S ribosomal RNA, a technique that has revolutionized microbiology. He also originated the RNA world hypothesis in 1967, although not by that name.
EnzymeAn enzyme is a biological macromolecule, usually a protein, that acts as a biological catalyst, accelerating chemical reactions without being consumed in the process. The molecules on which enzymes act are called substrates, which are converted into products. Nearly all metabolic processes within a cell depend on enzyme catalysis to occur at biologically relevant rates. A metabolic pathway is typically composed of a series of enzyme-catalyzed steps.
Reaction rateThe reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time or to the decrease in the concentration of a reactant per unit time. Reaction rates can vary dramatically.
Semipermeable membraneSemipermeable membrane is a type of synthetic or biologic, polymeric membrane that allows certain molecules or ions to pass through it by osmosis. The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Depending on the membrane and the solute, permeability may depend on solute size, solubility, properties, or chemistry.
RibozymeRibozymes (ribonucleic acid enzymes) are RNA molecules that have the ability to catalyze specific biochemical reactions, including RNA splicing in gene expression, similar to the action of proteinenzymes.*As an Amazon Associate I earn from qualifying purchases.