Answer: The difference between chemically defined and complex media is that the chemical defined contain an exactly known chemical composition while complex media contain an unknown chemical composition.
Explanation: if we grow microorganisms in laboratories, we must provide them with nutrients and conditions they need in order to get a good growth. There are growth media or culture media for this purpose. The culture medium is a solid, semi-solid or liquid substrate that is rich in nutrients and other necessary elements and supports the growth of microorganisms. We carry out isolation, identification, and maintenance of microorganisms on culture media. There are different types of culture media depending on the composition and use. Chemically defined media and complex media are two main types of these. Chemically defined media contain pure biochemical; hence, the chemically defined media contain exactly known chemical composition. However, complex media contain complex materials such as blood, milk, beef extract, etc., so the chemical composition of the complex media is unknown.
Chemically defined media are useful when studying the minimal requirements of microorganisms and for a variety of physiological studies. Furthermore, these media are useful in in vitro cell cultures of human and animal cells. Glucose salt broth is one example of such media. Peptone broth is another example.
Chemically complex media help to grow microorganisms that have complex nutritional requirements.
Furthermore, complex media are usually used for the cultivation of bacterial pathogens and other fastidious bacteria. Nutrient broth/agar, tryptic soy broth/agar, and blood agar are a few examples of complex media.
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