Proteins may act as buffers because the free carboxyl group can release hydrogen ions.
a) the free carboxyl group can combine with hydrogen ions.
b) the free carboxyl group can act as a base.
c) the free amino group can release hydrogen ions.
d) the free amino group can act as an acid.

Select the correct answer. which statement applies only to the axial skeleton, not the appendicular skeleton? a. it contains a pivot joint. b. it has muscles attached that work in pairs. c. it contains red bone marrow. d. it possesses fossa for bone articulation. e. it protects the heart and lungs.