Cell Transport and Homeostasis

Cell Transport & Homeostasis

• Homeostasis: The process of maintaining a balanced internal environment in cells and the body to ensure proper function.

• Cell Membrane: A semi-permeable barrier that regulates the movement of substances into and out of the cell.

Types of Transport

• Passive Transport: Does not require energy; substances move along their concentration gradient from high to low.

• Active Transport: Requires energy to move substances against their concentration gradient, from low to high.

  • Examples of Active Transport:

    • Sodium/Potassium Pump: An active transport mechanism that moves sodium out of cells and potassium into cells, crucial for maintaining cell function and heart health.

    • Endocytosis: The process where the cell membrane engulfs a substance, allowing the cell to "swallow" it using energy.

    • Exocytosis: The reverse process of endocytosis; it expels waste or unwanted materials from the cell, also requiring energy.

Passive Transport Mechanisms

1. Diffusion

• Definition: The natural spreading of molecules from areas of high concentration to areas of low concentration.

  • Example: The dispersion of scent from a fart in a room.

2. Osmosis

• Definition: The diffusion of water across a semi-permeable membrane, helping to maintain osmotic balance (the balance of solute concentrations).

3. Facilitated Diffusion

• Definition: The process of using channel proteins to assist larger or polar molecules in crossing the cell membrane, allowing them to pass through without energy.

Osmotic Balance

• Cells strive to balance concentrations of solutes inside and outside of themselves using osmosis.

• Types of Solutions:

  • Hypotonic:

    • Description: A solution with a higher concentration of solutes inside the cell than outside, causing water to move into the cell.

    • Result: The cell swells or may burst (lysis).

  • Isotonic:

    • Description: A solution where concentrations of solutes are equal inside and outside of the cell.

    • Result: Water is moving in and out at equal rates, maintaining cell shape and function.

  • Hypertonic:

    • Description: A solution with a higher concentration of solutes outside the cell than inside, causing water to exit the cell.

    • Result: The cell shrinks (crenates) due to loss of water.