Biology Blogs For Class11th, 12th and NEET

                                            Kreb Cycle  Krebs cycle is also known as the citric acid cycle or tricarboxylic acid cycle(TCA) . It was discovered by H.A.Kreb in 1953. Kreb Cycle cycle occurs in the matrix of the mitochondria . The whole cycle of Kreb is described in the following figure. The net result of the Krebs cycle is that acetyl group entering the cycle as acetyl- CoA, two molecules of carbon dioxide are produced.  Kreb Cycle Steps - Condensation - Acetyl CoA combines with oxaloacetic acid in the presence of citrate synthetase enzyme to form citric acid. It is the first product of the Krebs cycle. Dehydration -  Citric acid in presence of aconitase enzyme is converted into cis-aconitic acid. Water is released here. Hydration - Cis-aconitic acid is converted into isocitric acid with the addition of water in the presence of enzyme aconitase.  Dehydration -  Isocitric acid is oxidized into oxalosuccinic acid by reacting with NAD+ in the presen

                                              Virus  Viruses are simple noncellular entities consisting of one or more molecules of either DNA or RNA enclosed in a coat of protein. They become active only in living cells and they are intracellular parasites. The size of the virus is 0.02 to 0.03 micrometer but the size of the virus in smallpox is 200nm in diameter which is the largest size of the virus.  A fully assembled infectious virus is called a virion . " The main function of the virion is to deliver its genetic material into the host cells so that the genome can be expressed by the host cell. " Viral Structure - The structure of virions is very diverse, varying widely in size, shape, and chemical composition.  All viruses have a nucleocapsid composed of nucleic acid surrounded by a protein capsid. The capsid is formed as single or double protein shells and consists of only one or few structural protein species. The protein used to build the capsid is k