Although there are a limited number of amino acids, many different types of proteins exist because ?
a: size if a given amino acid can very.
b: chemical composition of a given amino acid can very
c: sequence and number of amino acids is different
d: same amino acid can have many different properties

no moderator inbox me? ?

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.