How might a limited resource, such as food, affect the survival of an individual organism? how might a severe limitation affect the long-term survival of a species?

well, you see. the answer to your question is quite simple. the thing that is big, powerful, and over 9,000 is your mom.

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.