Cell Cycle Regulation and Checkpoints

Study Notes

Cell Cycle Regulation

The cell cycle is regulated by a control system akin to a clock, involving both internal and external regulatory proteins.
Cells typically stop dividing when they come into contact with other cells, a process known as contact inhibition.

Checkpoints in the Cell Cycle

Checkpoints are critical control points where the cell cycle halts until a go-ahead signal is received. Major checkpoints occur at G1, G2, and M phases.
At the G1 checkpoint, a go-ahead signal prompts the cell to proceed with the S, G2, and M phases; absence of the signal leads to a non-dividing state called G0 phase.
The G2 checkpoint signals the cell to enter Mitosis.

Regulatory Proteins

Cyclins and Cyclin Dependent Kinases (CDKs) are essential regulatory proteins involved in coordinating the cell cycle.
Maturation Promoting Factor (MPF) is a cyclin-CDK complex that facilitates a cell's progression through the cell cycle.
Cyclins are one family of proteins regulating the cell cycle specifically in eukaryotic cells.

Internal and External Regulators

Internal regulators respond to internal cellular events, allowing the cell cycle to proceed only after certain prerequisites, such as chromosome replication and spindle fiber attachment, are met.
External regulators include proteins that respond to external stimuli, influencing the speed of the cell cycle; Growth Factors are examples that promote cell division.

Role of Growth Factors

Growth Factors are external regulatory proteins that stimulate cell growth and division, crucial during processes like embryonic development and wound healing.

Apoptosis

Apoptosis refers to programmed cell death characterized by distinct stages, including cell shrinkage and fragmentation of the cell membrane.

Cancer and Cell Growth

Cancer is a disorder where cells lose control over their growth mechanisms.
Cancer cells disregard the signals that typically regulate cell division, leading to uncontrolled proliferation and formation of tumors.
Defective genes, particularly the p53 gene, are often implicated in cancer development, resulting in disrupted cell cycle control.

Description

This quiz covers the mechanisms of cell cycle regulation, including critical checkpoints at various phases and the role of regulatory proteins such as cyclins and CDKs. Test your understanding of how cells control their division and the importance of each checkpoint.