The orientation of all the atoms of a protein in three dimensions represents its tertiary structure. It includes the folding of the polypeptide chains in a way that brings are far apart amino acids of its secondary structure close together. Various segments of a polypeptide chain interact to form tertiary structures and these segments are held together by different kinds of weak interactions.
However, disulfide cross-links between the segments of polypeptide chains also stabilize the tertiary structure of some proteins. Likewise, disulfide bonds also hold the protein subunits of some proteins together and thereby, contribute to the quaternary structure. For example, two light chains of an antibody are joined together by disulfide bonds.
A white blood cell engulfing foreign materials is more likely to carry out Endocytosis.
Explanation:
Endocytosis is the process by which a cell takes up a macromolecule into is cytoplasm by forming a vessicle.
In the question two cases are given, both the cases involve the formation of membrane bound vessicle but in different ways.
The excretion of hormones involves the movement of molecule outside the cytoplasm. This process is exocytosis.
The engulfment of an antigen by WBC involves taking up of molecule within the cell so that it can be killed and digested. Thus in this case Endocytosis is more likely to occur..
