From molecules to the first cell, Biology

Assignment Help:

From Molecules to the First Cell

The prebiotic conditions on the earth in all probability were volcanic eruptions, lightning and heavy rains. There was no trace of free oxygen or an ozone layer in the atmosphere to absorb ultraviolet radiations from the sun. It is assumed that organic molecules would have originated in such climatic conditions. This is described as their abiotic origin. Laboratory experiments from 1953 onwards prove that organic molecules like amino acids, proteins, nucleotides, nucleic acids, lipids and ATP can be formed in similar conditions on the earth. Stan1r.y Miller's experiment described below is one such experiment (Fig. shown below). It is possible that such organic molecules similar to those synthesised in Miller's experiment would have got accumulated at several places in high concentration, giving rise to a kind of liquid soup.

2287_molecule to 1st cell.jpg



Scientists have three different speculatiohs about the composition of a protobiont. Some consider it'as an aggregate of electrically charged molecules with water around them acting as a boundary and this is called as coacervate model (Fig. shown below). This model was proposed by Alexander Oparin. Sidney Fox proposed another model for protobiont formation called protenoid microsphere model. According to this model when water free mixtures of amino acids are heated at high temperature, they pol.yinerise to form protein-like molecules, called proteinoids. These can persist only if cooled quickly. According to a third model called as the lipid bilayer model of Richard Goldacre, an abiotically synthesised phospholipid bilayer was formed around a central space containing organic molecules. All such models are without any experimental or theoretical evidence. However, the supporters of each model try to explain how some life-processes like osmosis and budding, can be camed out by such protobionts.

1714_protobionts.jpg


Related Discussions:- From molecules to the first cell

Limitations of ecological pyramids, Limitations of Ecological Pyramids ...

Limitations of Ecological Pyramids The pyramid of energy is a significant improvement over the previous two types of ecological pyramids, yet all of them overlook one or anot

What is passive transport, What is Passive Transport? Passive Transpor...

What is Passive Transport? Passive Transport :  Specialized proteins called permeases also move specific substances across the cell membrane in a process called carrier transp

What is ribozymes , In at least single eukaryote, Tetrahymena, the ...

In at least single eukaryote, Tetrahymena, the pre-rRNA molecule holds an intron.  Erasing  of  the  intron  in running  processing  of  the  pre-rRNA  does  not require  the  assi

Diet counseling for a successful weight reduction programme, Explain the Di...

Explain the Diet Counseling for a successful weight reduction programme? As discussed above diet counseling is a very important aspect of a successful weight reduction programm

Explain the term health, Explain the term 'health' Mention any two ways of ...

Explain the term 'health' Mention any two ways of maintaining it. Why does a doctor administer tetanus antitoxin and not a tetanus vaccine to a child Injured in a roadside acci

The mirrows reach or grayling zone, The mirrows reach or grayling zone ...

The mirrows reach or grayling zone This zone has a less steep gradient, than the trout beck. The river here still flows swiftly, though the current is not fast and conditions

Walrasian model, Normal 0 false false false EN-IN X-N...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Explain the mechanisms of endosseous integration, Mechanisms Of Endosseous ...

Mechanisms Of Endosseous Integration Three terms may be used to describe individual aspects of bone formation process that can occur around implants. They are Osteoconduction,

Determine the uses of iron - soil, Determine the uses of Iron - Soil Ir...

Determine the uses of Iron - Soil Iron is a constituent of cytochromes, haem and non-haem enzymes. It is also essential for chlorophyll formation though is not a part of it. It

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd