Cell Biology Fundamentals

Cell Theory and Cellular Organization

• All living things are made of 1 or more cells, and cells work together to form body tissues, organs, and organ systems.
• Cells are specialized to work in different levels of organization, such as skin cells, stomach cells, and muscle cells.

Cell Cycle and Regulation

• The cell cycle is the process by which cells grow, replicate their DNA, and divide to make more cells.
• Cells are either in interphase (growing, replicating DNA, and doing cell functions) or M phase (mitosis and cytokinesis).
• The cell cycle is regulated by checkpoints to ensure that cells are growing and replicating DNA correctly before dividing.

Checkpoints in the Cell Cycle

• Checkpoints are present in G1, G2, and M phases to ensure that cells are growing well and replicating DNA correctly.
• G1 checkpoint: checks if the cell is growing well enough, if its DNA is damaged, and if it has the resources it needs.
• G2 checkpoint: checks if the DNA was replicated correctly in S phase and if the cell has the resources it needs.
• M phase checkpoint: checks if chromosomes are lined up correctly in metaphase.

Cell Cycle Regulation and Proteins

• Proteins play a crucial role in regulating the cell cycle, with some proteins acting as positive regulators and others as negative regulators.
• Cyclin and Cdk are examples of positive regulators that allow cells to move forward in the cycle.
• Negative regulators, such as p53, can initiate apoptosis (cell self-destruction) if a cell is damaged beyond repair.

Apoptosis and Cell Death

• Apoptosis is a mechanism by which cells self-destruct if they are damaged beyond repair.
• This ensures that damaged cells do not go on to divide and potentially cause harm.

G0 Phase and Cell Resting

• G0 is a resting phase where cells are not preparing to divide but are still performing cell functions.
• Some cells may go into G0 temporarily due to lack of resources, while others, such as neurons in the brain and spinal cord, may stay in G0 permanently.
• Cells in G0 phase do not divide and may have implications for healing in cases of injury.

Cell Theory and Cellular Organization

• All living organisms are composed of one or more cells, which work together to form tissues, organs, and organ systems.
• Cells are specialized to perform specific functions in different levels of organization, such as skin cells, stomach cells, and muscle cells.

Cell Cycle

• The cell cycle consists of interphase (growing, replicating DNA, and performing cell functions) and M phase (mitosis and cytokinesis).
• The cell cycle ensures that cells grow, replicate DNA, and divide to produce more cells.

Cell Cycle Regulation

• Checkpoints are present in G1, G2, and M phases to ensure that cells are growing and replicating DNA correctly before dividing.
• Checkpoints prevent cells with damaged DNA or insufficient resources from dividing.

G1 Checkpoint

• The G1 checkpoint evaluates cell growth, DNA damage, and resource availability before allowing cell cycle progression.

G2 Checkpoint

• The G2 checkpoint verifies that DNA replication occurred correctly in S phase and that resources are available for cell division.

M Phase Checkpoint

• The M phase checkpoint ensures that chromosomes are aligned correctly in metaphase before cell division.

Proteins in Cell Cycle Regulation

• Proteins regulate the cell cycle, with positive regulators (e.g., cyclin and Cdk) promoting cell cycle progression and negative regulators (e.g., p53) initiating apoptosis in damaged cells.

Apoptosis

• Apoptosis is a mechanism of programmed cell death that eliminates damaged cells to prevent harm.

G0 Phase

• G0 is a resting phase where cells perform functions but do not prepare to divide.
• Cells in G0 phase do not divide and may be temporarily or permanently arrested, with implications for healing in cases of injury.