Chapter 25: Origins of Life on Earth Flashcards
List the steps thought to be involved in generating de novo life on Earth.
- Synthesis of small organic molecules (monomers - i.e. amino acids)
- Joining small organic molecules together to build macromolecules (i.e. proteins, nucleic acids)
- Packaging of molecules into lipid vesicles – “protocells”
- Formation of self-replicating, heritable molecules that could serve as the instructions for life
All forms of life are built of _____ and built from ____ called ____.
organic macromolecules, units called cells
What monomers make up nucleic acids (DNA, RNA)?
Nucleotides
What monomers make up proteins?
amino acids
What monomers make up carbohydrates (also called starches)?
monosaccharides (also called simple sugars)
What monomers make up lipids?
fatty acids
Even the simplest cells have ___________.
heritable instructions for life
What hypothesis for the origin of small organic molecules was proposed by AI Oparin and JBS Haldane?
Energy input from high levels of UV radiation and lightning allowed for already present gases to react in a way that formed small organic molecules.
What did the Miller-Urey experiment demonstrate?
Proved Oparin’s hypothesis- with enough energy and certain atmospheric conditions they could make organic molecules in lab.
What is the second longest-held hypothesis for the origin of small organic molecules?
gases near volcanic openings were most suited for formation of life so small organic molecules appeared in separate small areas
Of the first two hypotheses for the origin of small organic molecules, which one generates more amino acids when simulated in lab?
Hypothesis 2- near volcanic openings
What is the third hypothesis for the origin of small organic molecules?
life began in oceans, where naturally acidic environment and minerals near hydrothermal vents created the perfect conditions for the formation of life.
It is possible that __________ aided in underwater formation of life according to the third hypothesis for the origin of small organic molecules.
pores containing catalysts
What is the fourth and most recent hypothesis for the origin of small organic molecules?
organic molecules came to earth on meteorites
What evidence exists for the fourth and most recent hypothesis for the origin of small organic molecules?
both old and recent meteors on Earth have been found which contain organic molecules
How did organic monomers first organize into polymers/macromolecules?
Either spontaneously or with catalytic assistance from sand or clay
Why does life need to be organized into a cell?
to contain essential molecules and optimize them for life
What are proto-cells?
simplest form of early cells- lipid vesicles
The presence of _________ accelerates the formation of vesicles.
clay called montmorillonite
What molecule provides heritable instructions for life in humans today?
DNA
What molecule provided heritable instructions for life in the earliest forms of life?
RNA
Why were early cells based on RNA?
simpler/single-stranded, can replicate itself w/o enzymes
Why did cells change from being RNA- to DNA-based?
DNA is more stable and has fewer replication errors which provides more viable offspring.
