Introductory Biology

12.1 How did life begin?

We are stardust! All life share a common origin. Earth was formed about 4.5 billion years ago, as well as the solar system. Earth separates the heavy elements to the middle, therefore the atmosphere surrounds it. Scientists have been able to estimate the age of the Earth by measuring the age of rocks found on Earth. Radiometric dating is used to estimate the age of an object by measuring its radioisotopes. Radioisotopes are unstable isotopes that breaks down + release energy in charged particles (radiation). **The breakdown is called radioactive decay. Half-life is the time it takes for one-half of a radiosotope decays to its breakdown products. In the radio active decayed curve, as you go deeper, your going back through time.

Fossils record all kinds of organisms that are not around today. The deeper we go into the rocks, the older the rock gets. (deeper = simpler) When the organism dies, they decompose and the bones are only left. The bones are carried around by scavengers and are buried + mineralized. After death, there is no more carbon (carbon 14) inside of you. It happens best to organisms that get buried quickly under the earth like: shells and organisms under the sea. Rocks contain uranium. One order of magnitude = 10 times older. Two orders of magnitude= 100 times older.

Scientists believe that natural chemical and physical processes lead the life on Earth. The energy in the environment combines inorganic molecules into organic compounds (carbon-containing molecules). Experiments have been tested to result that many of the organic molecules that are necessary for life can be produced from molecules of non-livng matter.

Scientist Oparin and Haldane created the primordial soup model, which was based on the presumed conditions of the early Earth. They hypothesized that the molecules were formed in chemical reactions activated by energy from: solar radiation, volcanic eruption, and lightning. Miller/Urey experiment tested the hypothesis that organic molecules could form from inorganic molecules. 1.) The early Earth’s conditions were imitated by a closed set of glassware. It was sealed to keep away from the surrounding atmosphere.Water was in the bottom to imitate the oceans. 2.) Heat was used to circulate the water vapor, to imitate the water cycle. The atmospheric gases included: nitrogen, methane, hydrogen and ammonia. NOT OXYGEN, thought to have been absent from the early Earth’s atmosphere. Electrical sparks used to simulate/imitate the lightning. A condenser cooled the gas, imitated rain. 3.) After some time, collected samples which had a variety of organic compounds: amino acids, fatty acids, and hydrocarbons.

The Miller-Urey model showed that the early Earth lacked an ozone layer and so the UV radiation would have destroyed any sort of ammonia or methane. Also, the experiment does not produce key organic molecules without methane and ammonia.

Luis Lerman produced the bubble model which propose that the oceanic hydrothermal vents played an important role in producing organic molecules. 

  1. Gases (ammonia, methane, and other gases from the eruptions of undersea volcanoes) were trapped in the underwater bubbles.
  2. Bubbles concentrate gases (allowed reactions) and the methane/ammonia needed to make amino acids were protected from UV radiation.
  3. Bubbles rose to the surface and organic molecules were released into the atmosphere as it burst.
  4. UV and lightning in the atmosphere provide more energy for further reactions/ producing complex organic molecules
  5. complex organic molecules fell into the ocean by the rain, beginning another cycle of reactions

RNA was probably the first genetic material. The relationship between RNA and protein is more direct than for DNA and protein. RNA is able to self-assemble (from molymer to polymers), self-replicate, and catalyze protein synthesis. RNA act as catalysts to make proteins & speed up reaction (used for metabolism, transcription, translation,etc.).  **Catalysts have a specific shape. So, RNA was likely the 1st information carrying, self-replicating, protein building molecule. The proteins RNA makes are going to be various. Amongst those proteins, some help in the translation process and others take RNA and copy its information into DNA. Microsphere are proteins that form a vesicle (group of tiny droplets of amino acids) that have some properties of membrane. Coacervates are combinations of proteins, lipids and carbohydrates that have some properties of membranes. RNA was probably the first cells required membranes and genetic material. DNA replaced RNA as the genetic material some time later.

Activation energy gets lowered to speed up a reaction. Enzyme controlling metabolism includes: helicases and polymerase. Information was placed inside of a membrane/a phospholipid biolyaer. Some ways to capture RNA (protobyons) were: put a bunch of lipids together (forms a sphere), heat then cool (microspheres), or combinations of lipids, proteins, and carbohydrates. Evolution is the competing of information molecules (the best copied molecule). Also have to make proteins.  


2 thoughts on “12.1 How did life begin?

  1. Yurika,

    Sorry, I just realized I read your blog and thought it belonged to Kenro! Ooops! Don’t worry, I figured out it’s your blog for 12.1.

    Mr. F.

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