Enzymes are protein, they are used to catalyse metabolisms in all organisms. They break down complex molecules and build up complex molecules from simple molecules, these two processes are catabolic reaction and anabolic reaction respectively. Enzymes are needed in these two processes to catalyse releasing and taking up ATP molecules.
Different sequence of amino acid produces different structure of protein, which determines the property of protein, thus each kind of enzymes has its unique active site, which only fits to complementary – shaped substrate to form product. Because of the feature of active site, each kind of enzymes therefore is specific for a particular reaction. However, there are several factors affect the rate of enzyme reactions, they are temperature, pH, concentration of enzyme, concentration of substrate and inhibitors. High temperature and pH affects the structure of enzyme, irreversible denaturation occurs, the shape of active site is changed, enzymes therefore no longer function. The effect of the other factors is slowing down the rate of enzyme reactions, it depends on the concentration of those factors. Since enzymes are catalyst of chemical reactions, they are responsible to the activities of cells, and they determine the function of tissues and organs as well.
In plant cells, during photosynthesis, enzymes are used in chloroplast to catalyse the processes. In light-dependent stage, ATP synthase enzyme is used to generate ATP molecules, they can be used in light-independent stage. Another enzyme, RuBisCo , catalyse the formation of glycerate-3-phosphate in Calvin cycle. The ATP generated in light-dependent stage and NADPH then react with glycerate-3-phosphate to produce triose phosphate, useful 6C sugar therefore is formed, for the growth of plants. In DNA replication, the enzyme DNA helicase is used to unwind and separate the two strands of DNA, breaking the hydrogen bonds between the base pairs. After nucleotides attach...
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