The two most abundant components of whole blood, in order of most abundant and second-most abundant, are

he is very short, and he can only reach halfway up on the elevator buttons. but on a rainy day, he has his umbrella with him, and he uses it to poke the button at the top.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.