Which of the following statements is true?
a) since all cells carry out cellular respiration they contain mitochondria.
b) a cell cannot be subdivided into smaller units that maintain the living state.
c) plant cells contain chloroplasts and no mitochondria while animal cells contain mitochondria and no chloroplasts.
d) the cell membranes function is to prevent diffusion of any substances into or out of the cell.
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the nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and dna, the building blocks of all life. plants absorb nitrogen in the form of ammonium, nitrate ion and, on rare occasions, as amino acids. animals receive nitrogen necessary for biological processes from feeding on living or dead organic matter.