Origin of Cells A2.1 Flashcards
What was oxygen like during pre-biotic Earth? What caused it?
concentrations very low because it reacted with methane and locked away in the Earth’s core
What was methane like during pre-biotic Earth? What caused it?
concentrations very high because of volcanic activity and meteorite bombardment
What was carbon like during pre-biotic Earth? What caused it?
concentrations very high because of emissions from volcanoes
What was ozone like during pre-biotic Earth? What caused it?
barely existed because of lack of O2, therefore UV radiation would have been higher
How would carbon compounds form during pre-biotic Earth?
- in specialized environments
- in droplets of water in the atmosphere
- deposited by rainfall into pools, lakes, seas. creating a “soup” of carbon compounds
What are some examples of carbon compounds that might have formed during pre-biotic Earth?
- carboxylic acid
- aldehydes
- amino acids
- nitrogenous bases
What does MRHGREN stand for and what does it do?
metabolism
response
homeostasis
growth
reproduction
excretion
nutrition
- characteristics of life, used to describe what is required to maintain life, not life itself.
How come viruses are not considered living?
viruses depend on a host for a living and therefore cannot maintain life on its own.
- cant make energy
- cant maintain stability
- cant grow, etc
What are the two theories for how life formed?
- abiogenesis
- biogenesis
What is abiogenesis?
life developed independently from non-living or inanimate substances. (spontaneous generation)
What is biogenesis?
complex life only arise from pre-existing living things through reproduction. (non-spontaneous gen)
What are necessary requirements for the evolution of first cells?
- catalysis
- self-assembly
- compartmentalization
- self-replication of molecules
What is catalysis?
to give control over which chemical reactions occur
What is self-assembly?
carbon compounds such as amino acids must assemble to form polymers
What is compartmentalization?
a membrane must be developed to enclose cell contents
What is self-replication of molecules?
as a basis for inheritance and the persistence of successful variants
What are some reasons cells could have arisen from non-living things?
- non-living synthesis of simple organic molecules
- simple organic molecules became assembled into more complex polymers
- these polymers became packaged into vesicles of diff internal chemistry
- certain polymers formed capacity to self-replicate (therefore inheritance)
What was the Miller-Urey experiment?
- evidence of carbon compounds origin
- simulated the atmosphere at early Earth
- created amino acid and carbon from a mixture of methane, ammonia, and hydrogen
Explain in steps what the Miller-Urey experiment did
- water boiled to reflect high temp in prebiotic Earth
- vapor mixed w/ gases (CH4, H2, NH3) to create a reducing atmosphere (no O2)
- electrical discharge (lightning) as energy source, led to reactions
- after cooling, a week later, traces of organic molecules are found
What are vesicles?
small droplets of fluid, enclosed in a membrane
- cell like but not yet proper cells
What are the membrane of vesicles composed of?
phospholipids
What happens when phospholipids mixed with water?
the phospholipid naturally self-assembles into bilayers, creating the basis for vesicles.
Why is the internal chemistry of vesicles different from its surroundings?
movement of polar molecules is limited
Why is RNA the presumed first genetic material?
- RNA can store info in the same way as dNA but is both self-replicating AND act as enzyme
- Replication needs enzyme actions
- enzymes need genes to be made
- can form complex 3D structures of polypeptides