Which of the following is true regarding membrane proteins?
a. all peripheral membrane proteins contact the lipid bilayer by covalent attachment to the hydrophilic head groups on membrane lipids
b. beta strands can assemble into a membrane-spanning barrel structure.
c. lipid-anchored membrane proteins always face the cell exterior.
d. a protein with six hydrophobic helices is most likely a lipid-anchored membrane protein .

Elephants in the savanna regions of africa dig holes in dried up river beds to reach water lying just below the surface. these holes provide drinking water for other animals as well. so, without the elephants, many animals might otherwise die from lack of water during the dry season. the location in which the elephants live is an example of a/n and the role they play in creating water holes is an example of a a) ecosystem; habitat b) community; niche c) habitat; niche d) niche; habitat

Why is earth's outer core hotter than earth’s oceanic crust? earth’s oceanic crust is denser than earth’s outer core is. earth’s oceanic crust has lava flowing from the mantle. earth’s outer core has a composition of solid iron and nickel. earth’s outer core is deeper within earth than oceanic crust is.

Tropical rain forests support more species per unit area than any other terrestrial ecosystem. what is one way rain forests are important to the health of the biosphere?