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

Objectives of psychological components, Objectives of psychological compon...

Objectives of psychological components It is essential to have objective scores, in order to identify and classify deficits in psychological components and processes. The nee

Taxonomy, newer trends of animal taxonomy

newer trends of animal taxonomy

What is gingival inflammation, What is Gingival Inflammation Areas of o...

What is Gingival Inflammation Areas of overt inflammation should be identified and the etiology investigated to initiate proper treatment.

Rate of conversion of atmospheric nitrogen into ammonia, The biological con...

The biological conversion of atmospheric nitrogen into ammonia in the group of plants known as legumes (peas, beans lentils and clover etc.) is achieved by the action of soil bacte

Write the meaning of hyperglycemia, Q. Write the meaning of Hyperglycemia? ...

Q. Write the meaning of Hyperglycemia? Hyperglycemia is a Greek term: hyper -meaning excessive; glyc - meaning sweet; and emia- means "of the blood". It is a condition in whic

Sugarcane, what the by products of sugarcane

what the by products of sugarcane

Which type of cell came first in evolution, Q. Which type of cell came firs...

Q. Which type of cell came first in evolution - the eukaryotic cell or the prokaryotic cell? This is an interesting problem of biological evolution. The majorly accepted hypoth

How sex occurs in bacteria, Q. How sex occurs in bacteria? Occurrence o...

Q. How sex occurs in bacteria? Occurrence of sex in bacteria was first described by Edward Tatum and Joshua Lederberg in 1946 (Nature, volume 158, page 558) who were studying m

How does the federal government regulate plant-incorporated, How does the f...

How does the federal government regulate plant-incorporated protectants and ensure their safe use in foods? EPA regulates the manufacture, sale and use of pesticides, containin

What is the futile cycle, What is the futile cycle The futile cycle is ...

What is the futile cycle The futile cycle is avoided because covalent modification, by  phosphorylation, has opposite effects on  the  enzymes concerned with  the  synthesis  a

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