Question

The essential requirements to maintain a living unit like the first cell are: organic energy sources; an information storage system; an expression system that uses the information to both exploit energy sources and to reproduce; and a method of containment to distinguish the living cell from the outside world. For each of the last three categories, identify the key molecules or groups of molecules used by the first cells that allowed them to maintain and propagate, and describe the properties/characteristics of these molecules that make them suited to these roles. As an example, the first category has already been done for you: “The first cells required sources of energy to power the reactions necessary to maintain homeostasis. These energy sources were in the form of chemical bonds found in organic molecules like carbohydrates and lipids. Carbohydrates range from simple monosaccharides like glucose, to more complex polysaccharides like starch. The covalent bonds of carbohydrates are relatively easy to break, making them an immediate source of energy. Because of their polarity, carbohydrates readily dissolve in the water-based solution of the cytoplasm, making them widely available. Lipid sources of energy are generally in the form of triglycerides (fats and oils). Lipids take longer to hydrolyze than carbohydrates, but lipids posses more energy per unit mass than carbohydrates. Their longer breakdown times and their hydrophobic nature make them excellent forms of long-term energy storage for the cell.”

Answer 1

##### Answer and Explanation #####

• An information storage system - The first cell required some information to generate the cell components , and biomolecules like protein, lipid etc. These informations are stored in the genome, in the form of DNA molecules , these are the polynucleotides made of nitrogenous bases ( A,T, G, C), sugar, and phosphate. These conatin some triplet codons that further transcribed into mRNA, further via translation it converts into protein i.e. Protein synthesis. With the help of protein synthesis genetic information is stored , in which DNA molecules play very crucial role.

• An Expression system that uses the information to both exploit energy sources and to reproduce - Protein synthesis or protein expression, the process where the information stored in DNA which are utilized for protein synthesis resuslting various types of protein molecules, Since protein is one of the most important component, and also works as eznyme, and ultimately enzymes are used by the cell system to exploit the energy from the sourcs in the process of respiration.

• A method of containment to distinguish the living cells from the outside world- In cells the components are limited by a membranous structure , known as plasma membrane or biological membrane mainly made of lipid, protein and carbohydrates. Some of the proteins which help in the transportation of the substances from outerside to the inner of the cell. Apart from the transport it protects the cell from the outer environment. like temperature , pH.

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