70- Biología celular. Regulación del ciclo celular

Introduction to Cell Cycle Regulation

Overview of Mitosis and Cell Cycle

• The session is led by Alejandra, a biology instructor, focusing on mitosis and the cell cycle.

• The discussion emphasizes the importance of understanding the regulation of the cell cycle, particularly after reviewing previous content.

Interphase and Decision to Divide

• Interphase consists mainly of G1 and S phases; G1 is when cells spend most of their time before deciding to divide.

• External stimuli such as hormones or growth factors signal cells to initiate division at a specific point in G1, termed the "control point."

Control Points in Cell Division

First Control Point: G1 Checkpoint

• At this checkpoint, cells assess internal and external conditions necessary for division.

Second Control Point: S Phase Verification

• During the S phase, cells verify that genetic material has been accurately replicated. Errors can lead to significant consequences.

Role of Proteins in Cell Cycle Regulation

p53 Protein Functionality

• The p53 protein plays a critical role in checking for replication errors; if severe errors are detected, it triggers programmed cell death (apoptosis).

Mitotic Spindle Checkpoint

• A third control point occurs during mitosis where chromosomes must be correctly aligned at the equatorial plane before proceeding with division.

Cyclins and Cyclin-dependent Kinases

Cyclin Dynamics

• Cyclins exhibit cyclical patterns of synthesis and degradation throughout the cell cycle, influencing cellular processes.

Role of Cyclin-dependent Kinases (CDKs)

• CDKs require association with cyclins to function effectively; they act as effectors that drive various stages within the cell cycle.

Activation Mechanisms for Cell Division

Formation of SPF Complex

• When cyclin concentration reaches a threshold, it forms an SPF complex (S-phase Promoting Factor), initiating DNA synthesis.

Transitioning into Mitosis

• After DNA replication concludes, cyclin levels drop. Increased concentrations of cyclin M associate with CDK2 to form MPF (M-phase Promoting Factor), facilitating entry into mitosis.

Summary of Key Regulatory Mechanisms

Recap on Molecular Participants

• Key molecules include cyclins and CDKs which form complexes that regulate transitions through different phases of the cell cycle.

Importance of External Stimuli