The amount of medicine in micrograms, A, in a person's bloodstream t minutes after a certain quantity of it has been inhaled can be approximated by the equation Upper A equals negative 5 t squared plus 50 t. How long after inhalation will there be about 105 micrograms of medicine in the bloodstream?

chemical weathering

explanation:

d. the weight of the book

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.