The movement of substances (as by diffusion) across a cell membrane without the expenditure of energy.
The answer is B . two atoms exchange electrons and become ions
As the ribosome reads each codon of mRNA, it directs tRNA to bring the specified amino acid into the ribosome. Each tRNA molecule carries<span> just one kind of amino acid. In addition, each tRNA molecule has </span>three unpaired bases<span>, </span>collectively called the anticodon<span>—which is complementary to one mRNA codon.</span>
They would constrict the diameter of blood vessels. Plaque and tobacco can block your arteries, inhibiting from doing their job.