Enzymes influence chemical reactions in living systems by a. Combining with excess hydrogen to form gaseous wastes
b. Affecting the rate (speed) at which reactions occur
c. Providing the substrate required for the reaction to occur
d. Absorbing water released when polymers are formed

Dwarf galaxies are select one: a. relatively rare. b. not very bright c. mostly spiral shaped. d. none of these.

Which of the following are causes of coastal erosion? check all that apply. beach grasses and other plants trap windblown sand. wave action carves away the coastline. groundwater under pressure is forced to earth’s surface. artificial structures stop the natural flow of sand along the coast. underground caves collapse as bedrock is dissolved.

Atypical human cell is approximately 12.00 μm in diameter and enclosed by a membrane that is 5.000 nm thick. (a) what is the volume of the cell including the membrane? (b) what is the volume of the cell membrane? (c) what percent of the total volume does its membrane occupy? to simplify the calculations, model the cell as a sphere. enter your answers using four significant figures.