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

Describe st segment depression, Q. Describe ST Segment Depression? The ...

Q. Describe ST Segment Depression? The development of ST-segment depression with exercise is probably the most reliable sign if myocardial ischaemia and appears to be the most

Suction force of the plant cell, What is meant by suction force of the plan...

What is meant by suction force of the plant cell? Does the suction force facilitate or make difficult the entrance of water in the cell? Ans) The suction force (SF) is the osmot

Counselling diabetic travellers, Counselling Diabetic Travellers The c...

Counselling Diabetic Travellers The counsellor needs to educate a diabetic patient and /or his family members to following issues when such patients plan to travel: ·  Plan

What is the life cycle type of bryophytes, What is the life cycle type of b...

What is the life cycle type of bryophytes? As in all plants the life cycle of bryophytes is diplobiontic (alternation of generations). In bryophytes the lasting form is the hap

Give the causative organism of bacillary dysentery, Give the causative orga...

Give the causative organism and symptoms of Bacillary Dysentery • Bacillary dysentery is caused by  Shigella sp. (Shigella sonnei, S. dysenteraei). Incubation period is

Explain the procedure estimation of the amount of bacteria, Explain the Pro...

Explain the Procedure Estimation of the Amount of Bacteria? Now carry out the exercise following the steps enumerated herewith. 1. Prepare ten fold dilutions of E. coli cult

What is the curvature of the lens, What is the curvature of the lens I...

What is the curvature of the lens In a human being and most other mammals, the first three mechanisms are not possible and accommodation occurs by the fourth mechanism only. T

Define food science and simple sugars, Define Food Science and Simple Sugar...

Define Food Science and Simple Sugars? This first unit introduces the concept, scope and importance of food science and technology as a discipline. It further presents a detail

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