I believe the correct word in the blank would be biological. I don't think anything else will fit in, especially when monomers of biological polymers are truly larger and more complex.
Acids and bases are important in living things because most enzymes can do their job only at a certain level of acidity. Cells secrete acids and bases to maintain the proper pH for enzymes to work. For example, every time you digest food, acids and bases are at work in your digestive system.
Answer:The nitrogen present in the soil is not directly used by the bacteria. It can be used only when the nitrogen is converted into usable form. These bacteria convert atmospheric nitrogen into ammonia, then nitrite which is then converted into nitrate. This nitrate is used by the roots of the plants like soybeans and peas. This is the role of bacteria present in the roots of the plant to convert atmospheric nitrogen into usable form that can be used by plants.
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