An antibody molecule has a molecular weight of 150 kD when analyzed by SDS polyacrylamide-gel electrophoresis (SDS-PAGE). Treatment with mercaptoethanol, a reducing agent that breaks disulfide linkages, yields polypeptides with molecular weights of 50 kD and 25 kD, and both of these bands are similar in intensity and thickness. Based on this gel pattern as described, what can we conclude about the molecular composition of the antibody molecule

The antibody has a molecular weight of 150 kD and consists of four subunits: two subunits of 50 kD and two subunits of 25 kD, which are bonded by covalent bonds.

Explanation:

Sodium dodecyl sulfate (SDS) is a detergent used to alter and denature proteins before gel electrophoresis. SDS can break hydrophobic interactions and hydrogen (H) bonds, but this detergent does not break down disulfide bonds, which is a type of covalent bond between two sulfur atoms. Moreover, mercaptoethanol is a reducing agent used to break disulfide bonds. In this case, it is expected that mercaptoethanol can break disulfide bonds between the four subunits of the mature antibody, thereby yielding two bands corresponding to the 50 kD and 25 kD bands (two subunits of 50 kD + two subunits of 25 kD = 150 kD).

prophase: we can observe the chromosomes to coil up and condense. they become visible. nuclear membrane and envelope disintigrate.s

metaphase: chromosomes align at the center, the metaphase plate. spindle fibers attach to centromeres of the sister chromatids. they meet at kinetochores.

anaphase: sister chromatids are pulled towards each opposing centromere, set on different poles.

telophase: chromosomes are now clustered up only on either sides of the cell. nuclear membranes reform, and a new cell wall forms along the cell plate. this will lead to cytokinesis, the process that divides the cell membrane and forms the cell wall.