IB Biology Topic A2.1: Origins of Cells Key Definitions

The origin of life from non-living matter, such as simple organic compounds.

A molecule with both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions, such as a phospholipid.

The process of increasing the rate of a chemical reaction by using a substance called a catalyst, which is not consumed during the reaction. Catalysts lower the activation energy needed for the reaction to occur, making it faster and more efficient.

A codon is a sequence of three nucleotides in DNA or RNA that specifies a particular amino acid or a start/stop signal during protein synthesis.

A gene sequence that has remained largely unchanged across species due to its essential role in survival.

The genetic code is a system that translates DNA instructions into proteins, the essential building blocks of life.

The last universal common ancestor of all present-day organisms, representing the root of the tree of life.

Natural selection is the process where individuals with traits better suited to their environment have higher reproductive success, passing these traits to the next generation.

A ribozyme is an RNA molecule capable of catalyzing specific biochemical reactions, similar to how protein enzymes function.

The RNA World Hypothesis is a scientific theory that suggests that RNA served as both the genetic material (storing information) and a catalyst (facilitating chemical reactions) before the evolution of DNA and proteins.

The ability of a system to maintain and regulate its internal order and functions (metabolism, energy use, repair, reproduction) independently, without requiring assembly from external agents.