Asample (723 mg) of an oligomeric protein of mr 151,000 was treated with an excess of 1‑fluoro‑2,4‑dinitrobenzene (sanger's reagent) under slightly alkaline conditions until the chemical reaction was complete. the peptide bonds of the protein were then completely hydrolyzed by heating it with concentrated hcl. the hydrolysate was found to contain 2.71 mg of dnp‑val. 2,4‑dinitrophenyl derivatives of the α‑amino groups of other amino acids could not be found. calculate the number of polypeptide chains in this protein. give the answer as a whole number.

the three components of a nucleotide are the nitrogenous base, the phosphate group and the five-carbon sugar.

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.