From molecules to the first cell, Biology

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

Posted Date: 12/8/2012 7:48:16 AM | Location : United States







Related Discussions:- From molecules to the first cell, Assignment Help, Ask Question on From molecules to the first cell, Get Answer, Expert's Help, From molecules to the first cell Discussions

Write discussion on From molecules to the first cell
Your posts are moderated
Related Questions
What is a goiter? What is endemic goiter? How is this problem socially solved? Goiter is the abnormal enlargement of the thyroid gland. The goiter appears as a tumor in the ant

Q. Procedures Adopted by Numerical Taxonomists? Since numerical taxonomy is an operational science, the procedure is divided into a number of repeatable steps, allowing the res

The depicted food web is not complete, mainly because:  a. The number of producers is less than the number of consumers. b. There are no decomposers. c. Only secondary co

Phytoflagellates – Protozoan Phytoflagellates are autotropbs that possess chlorophyll or other related pigments, and store food as fats, oils and starches (other than glycogen

How Vitamins and minerals work together with nutrients in food? Vitamins and minerals work together with nutrients in food. While antioxidant vitamins E and C and beta-carotene

Explain Risk Analysis Risk  Analysis  :  A  process  consisting of three components:  risk assessment,  risk  management  and risk communication

Diestrus- Estrous cycle This lasts 60 to 70 hours during which functional regression of the corpora lutea occurs. The uteri are small, anaemic, and only slightly contractile.

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

Explain about the Nutritional Requirements? Nutritional requirements are defined as 'intake levels of nutrients that meet specified criteria of adequacy such as normal growth,

Define Probability concept of requirements vs risk of deficient and excess intake? Figure best illustrates the concept of a requirement for an essential nutrient. The relations