Igneous rocks

Magma is a material present in the earth's crust, at depths between 10-100 km. It is generated by local heating and melting of rocks. Magma upon cooling, solidifies and crystallizes into a mosaic of minerals. These minerals are known as igneous rocks. Volcanic eruptions can also produce igneous rocks. A volcano is created when magma is extruded onto the earth's surface. Magma which creates a volcano is known as extrusive igneous rocks. Magma which gets solidified below the surface of the earth is known as intrusive igneous rock. The minerals contained in igneous rocks are quartz, feldspar, muscovite, biotite and mafics. The most abundant igneous rocks are granite and basalt. Some other examples for igneous rocks are Rhyolite, andesite, dolerite, diorite, gabbro and porphyry.

Regulation of metabolism by the mediation of enzyme

A good coordination of anabolic and catabolic processes is required for the growth and maintenance of a cell. The working of metabolic machinery is dependent on enzyme catalyzed reactions. Thus a fine control of enzyme catalyzed reactions is essential in the regulation of metabolism. For the study of these reactions, we can make use of both prokaryotic and eukaryotic organisms. There exist four major steps in metabolic regulation. They are compartmentation of enzymes, differentiating pathways for catabolism and anabolism of a key substrate, interaction of substrates with change in kinetic factors and control of enzyme activity and enzyme concentration. The factors which control the actual functioning concentration of the enzymes in a cell are the rates of enzyme synthesis and degradation. A prokaryotic cell is a cell with a plasma membrane. The plasma membrane acts as a substrate for organic enzymes. In a eukaryotic cell, compartmentation of metabolic machineries occurs for very specific purposes. A plasma membrane is associated with this cell too which serves the purpose of selective transportation of important cations, anions and neutral compounds. Metabolic reactions are always reversible which makes use of two types of enzymes. One enzyme is used for forward reaction and the other one for backward reaction. These reactions are called opposing unidirectional reactions or substrate cycles.