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

Explain fluids, Explain Fluids Fluids: Fluid diets are given to patien...

Explain Fluids Fluids: Fluid diets are given to patients with more advanced dysphasia or fractured jaws. The diet may include fruit juices, thin strained porridge with milk, e

Nursing responsibilities while administering immunization, NURSING RESPONSI...

NURSING RESPONSIBILITIES WHILE ADMINISTERING IMMUNIZATION Use one sterile syringe and needle for each injection.  Use only the diluent supplied along with measles and

Coccidioidomycosis, Coccidioidomycosis Coccidioidomycosis is a soil-...

Coccidioidomycosis Coccidioidomycosis is a soil-borne infection of pet, domestic, wild animals and  man. The disease is caused by Coccidioides immitis, a dimorphic fungus wh

Hybrid sterility, Hybrid sterility can be regarded as yet another form of i...

Hybrid sterility can be regarded as yet another form of interspecific sterility. The offspring of the interspecific crosses are mainly sterile. Geological studies have shown that t

What is the importance of pre procedural rinse, Q. What is the importance o...

Q. What is the importance of pre procedural rinse? Patients' use of an anti-microbial mouthwash of 0.12% chlorhexidine gluconate solution for 30 seconds prior to intra-oral pro

What are the abnormalities of gaze, What are the Abnormalities of gaze ...

What are the Abnormalities of gaze Normal gaze is when visual axes both eyes are parallel in primary gaze. when visual axes are not parallel in primary gaze, it is abnormal ga

How to calculate fractional shbrtening, Q. How to calculate Fractional Shbr...

Q. How to calculate Fractional Shbrtening? With the cursor- beam cutting the left ventricle just beyond the tips of mitral valve in an adequate parasternal long axis view,

Animal kingdom, If porifers shiw cell aggregate plan tgen how can they also...

If porifers shiw cell aggregate plan tgen how can they also shiw division of labour among cells

Examples of diseases normally spread by droplets, Q. (a) In droplet infecti...

Q. (a) In droplet infection (i) where do the droplets come from, (ii) what infective agents might they contain? (b) Give two examples of diseases normally spread

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