Oxygen and Electron Transfer

Topics: Oxygen, Iron, Redox Pages: 24 (6986 words) Published: November 11, 2009


CONTENTS 1. Introduction Metallobiomolecules 2. Classification Metallobiomolecules 2.1. Transport and of to

Storage Proteins
2.2. Oxygen binding Today scientists try to explore the chemistry basis behind the biological processes. As a result of this, new areas have evolved such as bioinorganic chemistry and bioorganic chemistry. In this section we will talk about an important concept in bioinorganic chemistry called “Metallobiomolecules”.

Metallobiomolecules 2.3. Electron Transfer Proteins 2.3.1. Cytochromes 2.3.2. Iron-Sulphur Proteins 2.4. Zinc Metalloproteins

1.0 Introduction to Metallobiomolecules
As we already know, biomolecules are molecules appear in biological systems to perform a specific function, like carbohydrates, proteins, lipids and nucleic acids. Metallobiomolecules are molecules associated with metal ions which play a major role in regulating biological processes, like biomolecules do. Characteristic feature of metallobiomolecule is as the name implies association of metal ion with molecular part. Classification of metallobiomolecules can be done based on several criteria. Let us consider the classification component.

2.0 Classification of Metallobiomolecules
As previously mentioned, association of metal ion is the characteristic feature of metallobiomolecules. That mean metal ion part is common for all metallobiomolecules. Depending on the nature of the other molecular part, metallobiomolecules can be divided into three categories.




1. Transport and Storage Proteins: Molecular part is belongs to the group of Proteins, but they are not enzyme and perform the transport and storage function. Myoglobin (Fe), Hemoglobin (Fe), Hemocyanin (Cu), Cytochromes (Fe) and Blue copper (Cu) Proteins are some examples. 2. Enzymes: Molecular part is belongs to the group of Proteins, and also they are enzymes. They perform the catalytic function. According to the type of reaction they catalyzed, they can further classified into three groups. Hydrolases : Carboxypeptidases (Zn) Oxido-reductases : Oxidases (Fe, Cu, Mo) Isomarases and synthestases : Coenzymes (Co) 3. Nonproteins Molecular part is a nonprotein group. Best example is Chlorophyll (Mg).

Let us discuss about transport and storage proteins first.

2.1.0 Transport and Storage Proteins
According to the function they perform, transport and storage proteins can be further divided into three groups like below. 1. Oxygen binding: Their function is to bind with oxygen and transport and storage the oxygen in body. 2. Electron carriers: Their function is to act as electron carriers and facilitate the electron transfer in biological processes. 3. Metal storage, carrier and structural Their function is to store metals and act as metal carriers.

2.1.1 Oxygen binding Metallobiomolecules Oxygen binding metallobiomolecules are molecules with metal ions associated with protein but non enzymatic molecular part and perform the oxygen transport and storage functions. During the evolutionary history of life, organisms have evolved these types of metallobiomolecules to make sure the efficient transportation of oxygen in their body which fulfill the oxygen demand of the body. In early evolution history of life transportation of oxygen is mainly through simple diffusion. Best example is amoeba. Simple diffusion as a transportation way is mainly governed by two factors: 1. Solubility of oxygen in water 2. Surface area to volume ratio Solubility of oxygen in water is very few. Therefore concentration of oxygen in water is less. Also when animal get bigger, surface area to volume ration get decrease. Diffusion of oxygen is mainly through body surface. Therefore simple diffusion is not enough when animal get bigger. Therefore animals evolved transport system to overcome this problem, where all the body cells meet their oxygen requirement. However still they used water as...
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