The cell cycle is regulated at the molecular level by a set of proteins known as:

A) ATPases B) separase proteins C) cohesins D) cyclins.

Answer: Option D.

Cyclins are proteins that regulate the cell cycle at molecular level.

Explanation:

Cell cycle refers to series of activities that take place in the cell leading to replication of DNA and division of cytoplasm to give two daughter cells. Cell cycle are regulated by a set of proteins called cyclins.

Cyclins are group of proteins the bind and activates cycling dependent kinases enzymes in order to control cell progression through the cell cycle.

D; cyclins

Explanation:

Cyclins as the name implies undergo a constant cycle of synthesis and degradation during cell division. When cyclins are synthesized, they act as an activating protein and bind to Cdks forming a cyclin-Cdk complex. This complex then acts as a signal to the cell to pass to the next cell cycle phase.