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

Oxygen - aquatic ecosystem, Oxygen - Aquatic Ecosystem Oxygen is found...

Oxygen - Aquatic Ecosystem Oxygen is found in waters in dissolved form. It enters the aquatic ecosystem through the air water interface and by the photosynthetic activities of

What is the tertiary structure of a protein, What is the tertiary structure...

What is the tertiary structure of a protein? What are the main kinds of tertiary structure? The tertiary protein structure is a spatial conformation additional to the secondary

Determine the photographic analysis, Photographic Analysis Documentatio...

Photographic Analysis Documentation is critical in any clinical procedure and more importantly in this field where due to the cost of the treatment involved, there is little ma

Parasites - biological stress, Parasites - Biological Stress Many inse...

Parasites - Biological Stress Many insects and microorganisms can feed upon tissues and saps of living plants. Hence plants must be protected against such parasites either by

Define the term- adaptation, Define the term- Adaptation The terms sco...

Define the term- Adaptation The terms scotopic and photopic vision are relative to the lighting conditions of an individual place. Light adaptation is a very quick process and

Gastro epiploic artery ge-other arterial conduits, Gastro Epiploic Arte...

Gastro Epiploic Artery (GE) :  Gastro epiploic artery is a less popular arterial conduit now. The midline chest incision is extended to the umbilicus and the right ga

Compare & contrast replication, Compare and contrast replication, transcrip...

Compare and contrast replication, transcription, and translation based on the following criteria.   Criteria Replication Transcription

Define role in glucose, Define Role in Glucose, Lipid and Nucleic Acid Meta...

Define Role in Glucose, Lipid and Nucleic Acid Metabolism? Chromium leads to a decrease in blood glucose concentration in people with elevated glucose levels and an increase in

CAM, Assignment on CAM

Assignment on CAM

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