Lesson 1 Flashcards
History of life
organic monomers
amino acids and nucleotides arose from inorganic compounds
It is proposed that life on earth began 3.5-4 billion years ago in a series of four stages:
- Organic monomers
- Organic polymers
- Protocells
- Living cells
Abiogenesis
The origin of life from nonliving matter
Oparin-Haldane Hypothesis
Primordial soup hypothesis (1920)
High levels of water vapor, hydrogen gas, methane, ammonia
these gases hold the elements essential for life: Carbon, hydrogen, nitrogen, oxygen
Miller-Urey (1953)
experimented with the gases from the Oparin-Haldane hypothesis to see if they would produce organic monomers- they did!
Iron-Sulfur World Hypothesis (late 1980s)
dissolved gases emitted from oceanic thermal vents can catalyze chemical reactions and create organic molecules
Extraterrestrial Origins Hypothesis
Bacteria-like cells evolved first on other planets and then were carried to earth
there is evidence of bacteria-like fossils being found in meteorite samples
Evolution of polymers
after monomers were formed, the next step is to join them together into their polymer forms, however, this process requires enzymes (proteins)
Iron sulfur world polymer explanation
Inorganic iron-nickel sulfides have a charged surface that attracted amino acids and binds them together
Protein-first hypothesis
proteins can polymerize abiotically when exposed to dry heat. could have pooled on the shore of early ocean and polymerized when exposed to heat from the sun
RNA-first hypothesis
RNA can act as both a substrate and an enzyme, so having RNA first would provide enzymes to catalyze polymer formation.
RNA would have to come from extraterrestrial sources
Stage 3: evolution of protocells
Before cells could arise, there had to be a primitive version to build upon. This focused most on the development of a cell membrane
Membrane-first hypothesis
The amphipathic properties of phospholipids could have allowed them to form membranes on their own
Stage 3: evolution of protocells: the next step in the development of cells would be the ability of protocells to process___.
food
Less is known about this process but there are hypotheses that the first protocells could have been photosynthetic, chemosynthetic, or heterotrophic
endosymbiotic theory
the mitochondria was once its own cell, was engulfed by a larger cell
