4)
during aerobic cellular respiration, combines with hydrogen ions and the product is released as a by-product of respiration.
a) adp
b) carbon
c) oxygen
d) acetyl coa

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.

we would need to see the picture to answer it

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.