Plant Physiology and Biochemistry: Botany Department, Faculty of Science, Damietta University

Organisms are capable of hundreds of chemical reactions. None of these reactions are possible without enzymes. Build-up of new tissues, replacement of old tissues, conversion of food to energy, disposal of waste materials, reproduction - all the activities that are characterized as "life". Enzymes are the substances that allow life to exist at earth temperatures. The living cell is the site of tremendous biochemical activity called metabolism. Metabolism is divided into anabolism and catabolism. Photosynthesis is the most obvious anabolic process in plants. It occurs in all green tissues and involves the reduction of CO2 to carbohydrates. However, respiration is a catabolic process which is responsible for generation of energy in living cells for all biological processes. Both anabolism and catabolism are exclusively under the control of enzymes. In addition, metabolism covers synthesis and breakdown of other groups of substances in plants, particularly lipids, protein nucleic acids etc?