AP BIOLOGY

Detailed explanation-1: -Cell cycle regulation is controlled via the action of enzymes call cyclin dependent kinases and cyclins. These enzymes control the progression of the cell through all phases of interphase, as well as mitosis.

Detailed explanation-2: -Cyclins are proteins that regulate the timing of the cell cycle in eukaryotic cells. Regulatory proteins are proteins that control the cell cycle both inside and outside of the cell. Internal regulators allow the cell cycle to proceed when certain events have occurred INSIDE a cell.

Detailed explanation-3: -Cell cycle progression is regulated in part by the sequential activity of various cyclins. The cyclins are regulatory subunits that bind, activate and provide substrate specificity for their catalytic partner serine-threonine kinases, collectively called cyclin-dependent kinases (Cdks) (reviewed in refs.

Detailed explanation-4: -The progression of cells through the division cycle is regulated by extracellular signals from the environment, as well as by internal signals that monitor and coordinate the various processes that take place during different cell cycle phases.

Detailed explanation-5: -Cyclins regulate the activity of their Cdk partners and also modulate their substrate specificity. More than 20 Cdk-related proteins and more than 11 cyclins have been identified in more complex eukaryotes, which has led to the concept that different cell cycle events are regulated by distinct cyclin-Cdk complexes.