Advanced Placement (AP) Biology Practice Exam

What does MPF stand for in the context of cell division?

1. M-phase promoting factor

2. Mitotic phase factor

3. Microtubule promoting factor

4. Mitosis progression factor

The correct answer is: M-phase promoting factor

In the context of cell division, MPF stands for M-phase promoting factor. MPF is a crucial protein complex that plays a significant role in the regulation of the cell cycle, particularly in the transition from the G2 phase to the M phase, which includes mitosis and cytokinesis. MPF is composed of cyclin and cyclin-dependent kinase (CDK), and it is responsible for the triggering of various cellular events necessary for mitosis. When cyclin levels rise during the G2 phase, they bind to CDK to form the active MPF complex. This activation leads to the phosphorylation of specific target proteins that facilitate the processes of nuclear envelope breakdown, chromosome condensation, and spindle formation, which are essential for successful cell division. The other terms listed in the choices do not accurately define MPF in the context of the cell cycle. While "mitotic phase" and "mitosis progression" might suggest a connection to the mitotic process, they lack the specificity to the cyclin-CDK complex that is fundamental to MPF’s function. The term "microtubule" also misrepresents the nature of MPF, as it is not solely focused on microtubule promotion but rather on the broader regulation of the