Oct 12, 2015

Take free online courses from world's top universities

  • Register on www.edx.org
  • Find courses
  • Start learning
  • Get certified from World's Top Universities
It includes the following universities

Apr 28, 2011

Hydrogen Bonding

What is hydrogen bonding?
A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond. These bonds can occur between molecules (intermolecularly), or within different parts of a single molecule (intramolecularly).
Intermolecular hydrogen bonding:
Intermolecular hydrogen bonding is seen in water molecule as a result of interaction between the oxygen and hydrogen atom of water molecule. Since oxygen is somewhat electronegative, it acquires electrons of both hydrogen atom towards itself and thus the oxygen atom seem to have negative charge while hydrogen with positive.The hydrogen bond is the result of interaction between these two charges.
Intermolecular Hydrogen bonding in water molecules
In the above fig. the dotted lines represents the Hydrogen bond between water molecules.

Apr 14, 2011

Peptide bond says "Proteins from aminoacids"

  Proteins are the body building materials of most of the organisms.Proteins are otherwise known as polymers of aminoacids.Two aminoacid is bonded through a peptide bond to form a peptide.Further these peptides are connected to form polypeptides, which on combination forms proteins.
Peptide bond:
The -NH2 group of one aminoacid makes a bond with -COOH of another aminoacid by giving out a water molecule to form -CONH.This is known as peptide bond.

Apr 12, 2011

E=mc^2 - Is it right?

The equation E=mc^2, given by Albert Einstein is the most significant one in the atomic level which paved the way for nuclear reactors, the future energy source to human being.Many people doubt this equation, but it can be solved by simple dimensional analysis.
Dimensional analysis is the simplest way to analyze whether the equation is dimensionally correct or not.
Basically it is based on three dimensions, namely mass(M), length(L), and time(T).
Dimensional analysis of E=mc^2 :
Let 'E' be the ..........L.H.S &
       mc^2 be the ............R.H.S
'E' refers to energy, which has the dimension of Force multiplied by displacement.According to newton, F=ma,

Apr 8, 2011

Aminoacid 2 - Arginine

Arginine is also an α-amino acid.
Molecular Formula :- C6H14N4O2
Molar mass :- 174.2 g mol−1
The amino acid side chain of arginine consists of a 3-carbon aliphatic straight chain, the distal end of which is capped by a complex guanidinium group.With a pKa of 12.48, the guanidinium group is positively charged in neutral, acidic and even most basic environments, and thus imparts basic chemical properties to arginine. Because of the conjugation between the double bond and the nitrogen lone pairs, the positive charge is delocalized, enabling the formation of multiple H-bonds.

3D structures:

Apr 7, 2011

Aminoacid 1 - Alanine

Alanine is an α-amino acid with the chemical formula CH3CH(NH2)COOH. Alpha α-carbon refers to the carbon directly bonded to the functional group.Here the carbon attached to the -COOH carboxylic group is called as Alpha carbon and hence it is named as alpha amino acid. It is classified as a nonpolar amino acid. D-Alanine occurs in bacterial cell walls and in some peptide antibiotics.
Molecular Formula :- C3H7NO
Molar mass :- 89.09 g mol−1
Appearance :- White powder
Solubility :- Soluble in water
Melting point :- 258 ºC
The α-carbon atom of alanine is bound with a methyl group (-CH3), making it one of the simplest α-amino acids with respect to molecular structure and also resulting in alanine's being classified as an aliphatic amino acid. The methyl group of alanine is non-reactive and is thus almost never directly involved in protein function.

Apr 6, 2011

Amino acids

 What are aminoacids?
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen. They are particularly important in biochemistry, where the term usually refers to alpha-amino acids.
An alpha-amino acid has the generic formula H2NCHRCOOH, where R is an organic substituent; the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (the α–carbon). Other types of amino acid exist when the amino group is attached to a different carbon atom; for example, in gamma-amino acids (such as gamma-amino-butyric acid) the carbon atom to which the amino group attaches is separated from the carboxylate group by two other carbon atoms. The various alpha-amino acids differ in which side-chain (R-group) is attached to their alpha carbon, and can vary in size from just one hydrogen atom in glycine to a large heterocyclic group in tryptophan.

Apr 3, 2011

We have done before E=mc^2, says Mahabharata

While testing the soil obtained from kurukshetra,the place where the historic, massive mahabharata war took place, the scientists came to a conclusion, that some atomic explosions might be took place, since the atomic radiations are seen in those samples.

It is also written in mahabharata as
...a single projectile
Charged with all the power of the Universe.
An incandescent column of smoke and flame
As bright as ten thousand Suns
Rose in all its splendor...

...it was an unknown weapon,
An iron thunderbolt,
A gigantic messenger of death,
Which reduced to ashes
The Entiure race of the Vrishnis and thr Andhakas.

Mar 31, 2011

Most efficient process ever known to man is Photosynthesis

Most of the science people are familiar with the laws of Thermodynamics.It is stated that "Energy is neither created, nor destroyed ; it can only be transformed from one state to another".For instance, Photosynthesis which converts the light energy into chemical energy.
The another important statement is that "It is impossible to construct an engine, which absorbs heat from a single body and transforms completely to work without losing some energy".For instance, combustion of petroleum products in combustion engines produces energy, which is never completely converted into workdone.It is proven that only an average of 30 to 40 % of energy is only converted to work obtained from combustion of fuels.
Based on this, the efficiency of a machine or a process is calculated given by the ratio of output to the input, multiplied by 100.The output may be the workdone or heat energy released, while the input may be the fuel, which is converted to energy to give the output.It is stated that,"Efficiency of a machine can never be cent percentage" which accompanies the second statement.Any engine with cent % efficiency are said to be perpetual engine, but it is hypothetical.While the most efficient man made process is fermentation whose percentage efficiency is about 57%.No man made engines exceeds the efficiency percentage of 60%.But the thing we can't make is being made by the nature, i.e Photosynthesis.It is scientifically proven that the average efficiency of photosynthesis in common plants is 70%.Let we know how it is.

Mar 15, 2011

Just travelling together can save our planet

videoDriving a 4 wheeler with 15 mpg economy emits 95 kilogram of Carbon dioxide to the atmosphere for every ten miles.But travelling in a public buses or trains can save a lot.