UNIT 2 - A 2.1 - Origin of Cells Flashcards
How old is Earth believed to be?
4.5 billion years old
How was Earth supposedly able to grow and temperatures on it rise?
There was no atmosphere so objects from space could hit Earth
What did carbon dioxide and methane allow, resulting in higher surface temperature?
UV light to penetrate the early atmosphere and retain heat
Why was there no ozone at the time?
Because free oxygen was not present
What were 7 of the possible components of Earth’s early atmosphere?
methane, ammonia, water vapor, carbon dioxide, hydrogen sulfide, hydrogen, nitrogen
What could have resulted in the spontaneous formation of many carbon compounds?
Earth’s early atmospheric components coupled with high surface temperatures and lightning, followed by gradual cooling
What are 7 functions of life?
Metabolism, growth, reproduction, response, homeostasis, nutrition, excretion
What is a result of metabolism?
Cells can convert one energy form to another
What does reproduction involve?
Hereditary molecules passed to offspring
What do organisms respond to which is essential for survival?
Stimuli
What does responding to stimuli allow organims to do?
Adapt to the environment
What does homeostasis refer to?
The maintenance of a constant internal environment (ex. temperature, acid-base levels)
What is the basis of nutrition?
Using a source of compounds with many chemical bonds that can be broken down to provide an organism with the energy necessary to maintain life
Why is excretion essential to life?
Because it allows chemical compounds which the organism can’t use/is toxic or harmful to be released from the organism’s system
What are the main principles of cell theory?
All organisms are made of one or more cells, cells are the smallest unit of life, all cells come from pre-existing cells
What are the hypothesized chemical/physical processes for a cell to evolve?
- Synthesis of small carbon compounds from abiotic molecules
- Small organic molecules joining to form polymers
- Polymers becoming contained by membranes, creating a protective homeostatic environment and separating the polymers fro their surroundings
- Development of self-replicating molecules so that inheritance and control can occur
What may enzymes allow for?
Small organic molecules joining to form a larger chain of molecules more rapidly
What are enzymes?
proteins that act as biological catalysts and accelerate chemical reactions
What do enzymes always contain?
Carbon and hydrogen
What are inorganic compounds?
Compounds that do not contain carbon (except for carbon dioxide)
What are organic compounds?
Compounds containing carbon
Why is carbon said to be the keystone element for life on Earth?
Because the complex organic compounds make life possible
Who conducted an experiment simulating prebiotic Earth conditions?
Stanley Miller and Harold Urey
What was the purpose of the Miller-Urey experiment?
To determine if gases supposedly on the prebiotic Earth could interact to produce the first stage in evolution
What gasses were used to make up the “atmosphere” in the Miller-Urey experiment?
CH4 (methane), NH3 (ammonia), H2 (hydrogen gas)
In the Miller-Urey experiment, what is heat used for?
Producing water vapor which rises to the chamber containing the simple compounds
What represented the lightning on earth in the Miller-Urey experiment?
Two electrodes in the chamber which produced 7500 volts at 30 amps
What was the condenser for in the Miller-Urey experiment?
Cold water flowed into it allowing for condensation
What molecules were found in the collection devide during the Miller-Urey experiment?
hydrocarbon chains and amino acids
What is a primordial soup?
A water-based sea of simple organic molecules
What were the strengths of the Miller-Urey experiment?
It modelled prebiotic earth and its atmosphere, showed that molecules such as amino acids can be spontaneously generated, the design of the experiment allowed for it to be replicated
What were the limitations of the Miller-Urey experiment?
We don’t actually know what the prebiotic atmosphere was like, not all of the organic molecules necessary for life were produced, the simulation could not account for all the conditions on prebiotic earth
What would the gasses be that made up the prebiotic atmosphere if it was true that the gasses were from volcanoes?
water vapor, carbon dioxide, sulfur dioxide, small amounts of carbon monoxide and hydrogen sulfide
What would a non-reducing environment result in?
Not in simple carbon compounds
What would a reducing environment be favourable for?
The development of carbon compounds
Which prebiotic atmosphere would result in a reducing environment?
The gasses used in the Miller-Urey experiment
Why does the Miller-Urey experiment contradict the primordial soup theory?
Because in a water environment, amino acids are not observed joining into more complex structures resulting in proteins, rather they break down into individual amino acids
What does the membrane of a cell provide?
A barrier/boundary between the inside of the cell and the surrounding environment
What does the membrane of a cell allow for?
the regulation and maintenance of activities within the cell
What are vesicles?
small, cell-sized double-layer bubbles formed when large numbers of fatty acids are placed in water
What can vesicles produced in a laboratory conduct?
important processes such as the ability to engulf other types of organic molecules, grow, replicate themselves
What is compartmentalization?
the development of a boundary around a vesicle
What does compartmentalization allow?
specialization of functions in different regions inside the outer protective fatty acid bilayer
What is hypothesized as the molecules that can allow inheritance and control the cell’s functions of life?
RNA
What organic molecules can RNA assemble spontaneously from?
nucleotides
How does RNA act as a type of genetic material?
It can form copies of itself
How does RNA act in an enzymatic role?
It has the ability to control chemical reactions
What are ribozymes?
a type of RNA
What is one role of ribozymes?
Catalysing activities, such as allowing faster development of peptide bonds
Why is the genetic role of RNA possible?
Because of the varying types of nucleotides present capable of combining to form a larger molecule
Why is RNA hypothesized to be the first genetic and controlling compound of a living cell rather than DNA?
Because of RNA’s simplicity and ability to form spontaneously
What are the major stages in the origin of life?
early earth - abiotic chemical compounds - small organic molecules - polymers of organic molecules - protocell - cell
What does LUCA stand for?
Last Universal Common Ancestor
What is the evidence for the existence of a LUCA?
- a universal genetic code carried by DNA, shared by all cells
- 300+ genes of DNA common to all cells
- same building blocks for DNA and RNA in all cells
- common molecular processes within all cells (ex. replication of DNA, production of proteins)
- similar transport mechanisms for cellular materials in and out of cells and within cells
What does the earliest evidence of life on Earth come from?
Fossils
What are fossils?
the remains/traces of past life
When is the earliest life occurance on Earth estimated?
3.5 billion years ago
What is half-life?
the length of time it takes for half of a radioactive isotope to change into another stable element
What is an isotope?
An unstable form of an element
How can the age of a fossil be determined?
by measuring the amount of an isotope in a fossil and comparing it with the amount taken up when the organism was alive
Why is the technique for dating fossils called absolute dating?
Because the half-life of each isotope is not known to vary
What does relative dating involve the use of?
the sediment layers of the earth and index fossils
What are sediements?
particles of eroded and weathered rock and soil which may create layers/strata
What may disturb the original sequence of sediment layers?
Geological processes
Why would it matter that the original sequence of sediment layers are disturbed?
Because the sequence has the oldest layers at the bottom so the fossil ages could be innacurate
What are index fossils?
fossils of the same age found in strata in different parts of the world
What are hydrothermal vents?
places where hot water emanates from beneath the ocean floor
How are hydrothermal vents formed?
when cracks in the crust of the seabed expose sea water to rocks below which are heated by magma
What discovery disproves the idea that the bottom of the ocean is lifeless and is evidence that the earliest life forms could have formed around hydrothermal vents?
communities living around hydrothermal vents
How are tube worms living around hydrothermal vents nourished?
they absorb the minerals from the water and transfer them to symbiotic bacteria which then make food from the minerals
What is evidence that supports the possible appearance of the LUCA at hydrothermal vents?
- some of the oldest fossilized traces/precipitates have originated at the hydrothermal vents
- the commonality of genetic sequences in the organisms near the vents
- presence of a minera-rich environment with both the acidic and basic fluids necessary for chemical reactions
- presence of hydrogen and carbon dioxide at vents resulting in reducing environment
What do reducing envirnoments support bonds between?
Hydrogen and carbon
