Why is energy needed?

Why is energy needed?

Like all other living things, microorganisms need to acquire energy in order to survive. Energy is required:

·              to maintain the structural integrity of the cell by repairing any damage to its constituents

·              to synthesise new cellular components such as nucleic acids, polysaccharides and enzymes

·              to transport certain substances into the cell from its surroundings

·              for the cell to grow and multiply

·             for cellular movement.

Metabolism is the term used to describe all the biochemi-cal reactions that take place inside a cell; it includes those reactions that release energy into the cell, and those that make use of that energy. Figure 6.1 summarises these processes.

As we saw, most microorganisms ob-tain their energy from the nutrients they take into the cell; these may come from an organic or an inorganic source. Once inside the cell, these nutrients must then be biochemically processed by reactions that trap some of their chemical energy, at the same time breaking them down into smaller molecules. These then serve as building blocks for the synthesis of new cellular com-ponents. Chemical compounds contain potential energy within their molecular structure, and some of this can be

released when they are broken down. In other metabolic types, energy is obtained from the sun by means of photosynthesis; once again, however, the energy is used for synthetic purposes.

Central to the metabolic processes of any cell are enzymes. Without them, the many biochemical reactionsreferred to above simply wouldn’t take place at a fast enough rate for living cells to maintain themselves. We shall start our consideration of metabolism by taking a look at enzymes: what they are, and how they work.