The interaction of which two systems provides the molecules needed for the metabolic activity that takes place at ribosomes?
(1) digestive and circulatory
(2) reproductive and excretory
(3) immune and nervous
(4) respiratory and muscular

The correct answer is (1) digestive and circulatory

Explanation:

Digestive system helps in digestion of complex organic matter present in the food like polysaccharides, proteins, lipids, etc. So due to the function of the digestive system, these complex molecules are converted into simpler forms like glucose, amino acids, etc. Then these simpler forms are absorbed in the body through intestine.

Ribosomes help in the production of proteins which requires amino- acids so the absorbed amino acids are moved into the cells through the circulatory system. Therefore digestive system and circulatory system provide the molecules required for metabolic activities.

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the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.