Cell Growth Limitations and the Cell Cycle

Cell growth is limited by several factors, which necessitate cell division:

1. DNA overload: As a cell grows, there may not be enough DNA to support its increased size.
2. Surface area to volume ratio: The cell's volume increases faster than its surface area, making it difficult for larger cells to efficiently exchange materials with their environment.

Definition: Chromosomes are structures that carry DNA, the genetic information passed from one generation to the next. Humans have 23 pairs of chromosomes.

The cell cycle consists of several phases:

1. Interphase:
   • Gap 1 (G1): Cell growth, longest phase
   • S phase (Synthesis): DNA replication, doubling the DNA set
   • Gap 2 (G2): Cell prepares for mitosis
2. Mitosis (M phase): Division of the nucleus
3. Cytokinesis: Division of cytoplasm and organelles

Highlight: Understanding the 4 stages of cell cycle is crucial for comprehending how internal and external regulators control mitosis.

Cell division is controlled by various mechanisms:

• Contact inhibition: Cells stop growing when they come into contact with other cells
• Cyclins: Proteins that regulate cell cycle timing
• Internal and external regulators

Vocabulary: Uncontrolled cell division can lead to the formation of tumors.

Example: Cancer cells differ from normal cells in that they don't respond to signals that regulate growth. This results in uncontrolled cell division, which is a hallmark of cancer.

Factors that can cause uncontrolled cell division include:

• Smoking and drug use
• Radiation exposure
• Fungal infections
• Genetic defects
• Excessive alcohol consumption

Highlight: Understanding the relationship between the cell cycle and cancer is crucial for developing treatments and prevention strategies for this disease.