Cell Biology: Cell Membrane and Mitosis

Cell Membrane

• Also known as the plasma membrane
• Semi-permeable membrane that surrounds the cell
• Composed of:
  • Phospholipid bilayer (phospholipid molecules with hydrophilic heads and hydrophobic tails)
  • Proteins (integral and peripheral)
  • Cholesterol (regulates fluidity and permeability)
• Functions:
  • Regulates what enters and leaves the cell
  • Maintains cell shape and structure
  • Provides mechanical support and protection

Mitosis

• Type of cell division that results in two daughter cells with the same number of chromosomes as the parent cell
• Occurs in somatic cells (non-reproductive cells)
• Stages:
  1. Interphase (cell growth and preparation)
  2. Prophase (chromatin condenses, nuclear envelope breaks down)
  3. Metaphase (chromosomes align at the center of the cell)
  4. Anaphase (sister chromatids separate)
  5. Telophase (nuclear envelope reforms, chromatin uncondenses)
  6. Cytokinesis (cytoplasm divides, cell splits)

Cell Division

• Process by which a cell becomes two daughter cells
• Types:
  • Mitosis (somatic cells, results in two identical daughter cells)
  • Meiosis (reproductive cells, results in four non-identical daughter cells with half the number of chromosomes)
• Cell division is necessary for:
  • Growth and development
  • Tissue repair and replacement
  • Maintenance of tissues and organs

Cytoplasm

• Jelly-like substance inside the cell membrane
• Composed of:
  • Water (about 70%)
  • Salts
  • Sugars
  • Proteins
  • Organelles (e.g. mitochondria, ribosomes, lysosomes)
• Functions:
  • Provides mechanical support and shape to the cell
  • Plays a role in cell signaling and communication
  • Involved in cell metabolism and energy production
  • Supports the movement of organelles and molecules within the cell

Cell Membrane

• The cell membrane is semi-permeable, allowing certain substances to pass through while keeping others out.
• The phospholipid bilayer is composed of hydrophilic heads and hydrophobic tails, which allows it to regulate the movement of substances across the membrane.
• Proteins embedded in the membrane, including integral and peripheral proteins, play a crucial role in the membrane's functions.
• Cholesterol helps regulate the fluidity and permeability of the membrane.

Mitosis

• Mitosis is a type of cell division that occurs in somatic cells, resulting in two daughter cells with the same number of chromosomes as the parent cell.
• During prophase, chromatin condenses, and the nuclear envelope breaks down, allowing the chromosomes to move to the center of the cell.
• In metaphase, the chromosomes align at the center of the cell, attached to the spindle fibers.
• Anaphase is characterized by the separation of sister chromatids, which move to opposite poles of the cell.
• During telophase, the nuclear envelope reforms, and chromatin uncondenses, resulting in two identical daughter nuclei.

Cell Division

• Cell division is essential for growth, development, tissue repair, and replacement, and maintenance of tissues and organs.
• The two main types of cell division are mitosis and meiosis, which differ in the number of daughter cells produced and the number of chromosomes they contain.

Cytoplasm

• Cytoplasm is a jelly-like substance that makes up about 70% of the cell's volume, providing mechanical support and shape to the cell.
• The cytoplasm is composed of water, salts, sugars, proteins, and organelles, such as mitochondria, ribosomes, and lysosomes.
• Cytoplasm plays a crucial role in cell metabolism, energy production, and cell signaling and communication.