In anatomical terms, proximal refers to a location towards the center of the body, while distal refers to a location away from the center of the body. using these terms, what effect will wrapping a tight band around the arm for a period of time have on blood flow?
it will increase blood pressure both proximal and distal to the band.
it will increase blood pressure proximally from the band.
it will decrease blood pressure both proximal and distal to the band.
it will decrease blood pressure proximally from the band.

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.

it provides an alternative energy pathway for the reaction to proceed.

a catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction.

catalysts increase the rate of reaction without being used up. they do this by lowering the activation energy needed. with a catalyst, more collisions result in a reaction, so the rate of reaction increases. different reactions need different catalysts.

a catalyst works by providing an alternative reaction pathway to the reaction product. the rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.