Test: Bio Inorganic- 1 - Chemistry MCQ

Corrin is a heterocyclic compound. It is the parent macrocycle related to the substituted derivative that is found in vitamin B12. Its name reflects that it is the "core" of vitamin B12 (cobalamins)

Chemical Structure of Superoxide Dismutase:

• Methemoglobin is hemoglobin in the form of metalloprotein, in which the iron in the heme group is in the Fe³⁺ state, not the Fe²⁺ of normal hemoglobin.
• Methemoglobin cannot bind oxygen, which means it cannot carry oxygen to tissues.
• It is a bluish chocolate-brown in colour.

• An essential element is one that is required for life and whose absence results in death.
• Because of the experimental difficulties involved in producing deficiencies severe enough to cause death, especially for elements that are required in very low concentrations in the diet.
• An element is considered to be essential if a deficiency consistently causes abnormal development or functioning and if dietary supplementation of that element—and only that element—prevents this adverse effect.
• The essential mineral elements are Nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, chlorine, iron, manganese, zinc, copper, molybdenum, and nickel.

 To stabilize negative charges on reaction intermediates

The primary function of the metal ion in metal ion catalysis is to stabilize negative charges on reaction intermediates.

Key Points

• Stabilization of negative charges:
  • Metal ions in catalytic processes often stabilize negatively charged intermediates, which can be crucial for the reaction to proceed.
  • This stabilization lowers the activation energy, making the reaction more feasible.
• Coordination chemistry:
  • Metal ions can coordinate with substrates to form more reactive complexes, facilitating the reaction.

Least conjugation is present in Vitamin B12 as one side of the corrin ring doesn’t have methylene linkages. In Heme, there is extensive conjugation of π electron (11 π ) as compared to that of chlorophyll.( 10π )

• Cytochromes P450 (P450) are hemoproteins encoded by a superfamily of genes nearly ubiquitously distributed in different organisms from all biological kingdoms.
• The reactions carried out by P450s are extremely diverse and contribute to the biotransformation of drugs, the bioconversion of xenobiotics, the bioactivation of chemical carcinogens, the biosynthesis of physiologically important compounds such as steroids, fatty acids, eicosanoids, fat-soluble vitamins and bile acids, the conversion of alkanes, terpenes and aromatic compounds as well as the degradation of herbicides and insecticides.
• Cytochromes P450 belong to the group of external monooxygenases and thus receive the necessary electrons for oxygen cleavage and substrate hydroxylation from different redox partners. The classical as well as the recently discovered P450 redox systems.
• Myoglobin contains a heme (prosthetic) group which is responsible for its main function (carrying of oxygen molecules to muscle tissues). Myoglobin can exist in the oxygen free form, deoxymyoglobin, or in a form in which the oxygen molecule is bound, called oxymyoglobin. Myoglobin is a protein found in muscles that binds oxygen with its heme group like haemoglobin.
• Oxidation of the iron atom (Fe2+ -> Fe3+) is mainly responsible for the colour of muscle and blood.

Hemocyanin, a copper-containing protein chemically unlike haemoglobin, is found in some crustaceans.

Hemocyanin is blue in colour when oxygenated and colourless when oxygen is removed.

• The reduction of nitrogen to ammonia, carried out by the enzyme nitrogenase is known as Nitrogen Fixation.
• Biological nitrogen fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia by an enzyme called nitrogenase.
• The reaction for BNF is: N₂ + 8H⁺ + 8 e^- → 2NH₃ + H₂
• This type of reaction results in N₂ gaining electrons and is thus termed a reduction reaction.