Origin of Cells Flashcards

Flashcards on the origin of cells, including abiotic early Earth, the origins of first protocells, and LUCA.

Cell Theory

States that cells are the smallest units of life.

NASA Definition of Life

A self-sustaining chemical system capable of Darwinian evolution; according to this definition of life, cellular structure is not a requirement.

Hadean Eon

The period from 4.5 to 4.0 billion years ago that is called after Hades due to frequent volcanic eruptions, meteorites, lightning and high temperatures.

Inorganic Molecules

Do not have both carbon and hydrogen within the same molecule. Usually have a small number of atoms and are often associated with non-living matter.

Organic Molecules

Contain carbon and hydrogen. Can be large molecules with many atoms and are usually associated with living organisms.

Miller-Urey Experiment

Tested whether simple carbon compounds can form from inorganic compounds; determined that simple organic molecules can form from inorganic compounds under conditions that simulated Early Earth.

LUCA

The last universal common ancestor of all life on Earth

Biomarkers

The molecular fossils of lipids and other organic compounds that are encased in sedimentary rocks and can remain intact over hundreds of millions of years.

Stromatolites

Structures created by photosynthetic bacteria that live in shallow water; the earliest known fossils are dated at 3.5 billion years ago.

RNA World Hypothesis

The idea that before living cells, the DNA genetic code, and the gene/protein cycle ever existed, chains of a chemical called RNA were forming naturally.

Inferred Qualities of LUCA

A small, single-celled prokaryotic cell that was an obligate anaerobe, a chemoautotroph, and was able to live in extreme heat. It obtained energy from hydrogen and converted carbon dioxide and nitrogen into essential organic compounds.

Trouble with a list-based definition of life?

Many counter-examples do not meet all criteria. Mature red blood cells do not contain DNA. Aseptate fungal hyphae are not divided into individual cells. Mules are sterile. Coxiella burnetii cannot reproduce outside its host cell.