1. Structure and Function of Cytoskeleton Filaments
1.1. Microfilaments (Actin filaments)
1.1.1. Structure:
1.1.1.1. Two intertwined strands of actin
1.1.2. Function:
1.1.2.1. Cell shape, motility, and division (cytokinesis)
1.1.3. Role in Cell Division:
1.1.3.1. Form the contractile ring during cytokinesis
1.2. Intermediate Filaments
1.2.1. Structure:
1.2.1.1. Fibrous proteins coiled into cables
1.2.2. Function:
1.2.2.1. Maintain cell shape and anchor organelles
1.2.3. Role in Cell Division:
1.2.3.1. Provide structural support
1.3. Microtubules
1.3.1. Structure:
1.3.1.1. Hollow tubes made of tubulin dimers
1.3.2. Function:
1.3.2.1. Maintain cell shape, intracellular transport, and chromosome separation
1.3.3. Role in Cell Division:
1.3.3.1. Form the mitotic spindle
2. Mitotic Spindle
2.1. Structure:
2.1.1. Composed of microtubules originating from centrosomes
2.1.2. Includes kinetochore microtubules, polar microtubules, and astral microtubules
2.2. Function:
2.2.1. Segregates chromosomes into daughter cells during mitosis
2.3. Importance:
2.3.1. Ensures accurate chormosome distribution to prevent aneuploidy
2.4. Impact of Mutation:
2.4.1. Mutations in spindle components can lead to improper chromosome segregation, resulting in cell cycle arrest of aneuploidy
3. Cell-Cycle Checkpoints and Cdks
3.1. Checkpoints:
3.1.1. G1/S Checkpoint:
3.1.1.1. Ensures cell is ready for DNA synthesis
3.1.2. G2/M CheckpointL
3.1.2.1. Ensures cell is ready for mitosis
3.1.3. Metaphase Checkpoint:
3.1.3.1. Ensures chromosomes are properly aligned
3.2. Activation of Cdks
3.2.1. Cdks (Cyclin-dependent kinases) are activated by binding to specific cyclins
3.2.1.1. Cyclin D activates Cdk4/6 (G1 phase)
3.2.1.2. Cyclin E activates Cdk2 (G1/S transition)
3.2.1.3. Cyclin A activates Cdk2 (S phase)
3.2.1.4. Cyclin B activates Cdk1 (G2/M transition)
3.3. Regulation of Checkpoints:
3.3.1. Activated Cdk-cyclin complexes phosphorylate target proteins to progress the cell cycle
3.3.2. Ensure proper DNA replication and repair before cell division
4. Additional Details
4.1. Phases of the Cell Cycle:
4.1.1. G0 Phase: Resting phase where the cell is not actively dividing
4.1.2. G1 Phase: Cell grows and synthesizes proteins necessary for DNA replication
4.1.3. S Phase: DNA replication occurs
4.1.4. G2 Phase: Cell prepares for mitosis, checks for DNA damage
4.1.5. M Phase: Mitosis and cytokinesis occur, resulting in the formation of two daughter cells
4.2. Regulatory Proteins:
4.2.1. p53: Tumor Suppressor protein that regulates the cell cycle and prevents genome mutation
4.2.2. Rb (Retinoblastoma protein): Regulates the cell cycle by inhibiting progression from G1 to S phase
4.3. Mitotic Phases
4.3.1. Prophase: Chromosomes condense, spindle fibers form
4.3.2. Metaphase: Chromosomes align at the metaphase plate
4.3.3. Anaphase: Sister chromatid separate and move to opposite poles
4.3.4. Telophase: Nuclear envelopes reform around separated chromosomes
4.3.5. Cytokinesis: Division of the cytoplasm, resulting in two daughter cells