Peripheral membrane proteins (select one):

A) penetrate deeply into the lipid bilayer.
B) are usually denatured when released from membranes.
C) can be released from membranes only by detergent treatment.
D) are generally noncovalently bound to membrane lipids.

Peripheral membrane proteins (select one):

D) are generally noncovalently bound to membrane lipids.

Explanation:

Peripheral membrane proteins are membrane protenis that adhere only temporarily. These don't penetrate deeply into the lipid bilayer, just penetrate the peripheral regions.  Also they are bound to either face of the membrane by noncovalent interactions. There are many different categories of peripheral membrane proteins: Membrane-targeting domains; transporters of small hydrophobic molecules ; electron carriers ; Polypeptide hormones, toxins, and antimicrobial peptides; structural domains; enzymes.

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.