Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
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.
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.
Define Conjugation in brief. A form of sexual reproduction in ciliates (Ciliophora). During conjugation two ciliate protozoans join and macronuclei disappears. After meiotic d
What are the three main parts into which a neuron can be divided? What are their respective functions? The three mains parts into which a neuron can be didactically separated a
Q What are the bacteriophages? Bacteriophages are viruses specialized in parasitism of bacteria. They are used in genetic engineering as molecular cloning vehicles to include r
Hemicryptophytes - Classes of Life Form In this case the perennating buds or organs are situated at the soil surface where they are protected by soil and fallen leaves. These
Inorganic Substances - Abiotic Components There are about forty elements that are required in various processes of living organisms. Some of these are macronutrients which the
Explain the Decolourizing Agent - Ziehl-Neelsen Method? Acid alcohol - a mixture of 95% ethanol and 3% HCI - is used for decolourization. Before decolourization, smear is allow
What is Anatomic concavities Anatomic concavities present in the lingual surface of the mandible, the sublingual fossa anteriorly and the submandibular fossa posteriorly. Norm
Locomotory Structures Annelids possess three kinds of locomotory structures, namely parapodia, setae and suckers. Parapodia are segmentally arranged, lateral, hollow extensio
From where does the cell get oxaloacetic acid for krebs citric acid cycle? Oxaloacetic acid is also formed when pyruvate is acted upon by pyruvate carboxylase in response to an
Pericardial Effusion: Indications for Surgery: Pericardial effusion may be the result of peiicarditis due to infection, autoimmune disease or neoplasm. Non-inflammatoly diseases
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!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd