Cellular Transport and Communication Notes

Transportation

  • Active Transport: Moves materials against concentration gradients, requiring energy.
    • Small molecules/ions transported by proteins.
    • Larger molecules/clumps transported via endocytosis/exocytosis.

Molecular Transport

  • Small molecules/ions carried by proteins.
  • Cells expend considerable energy to move ions like calcium, potassium, and sodium.
  • Enables cells to concentrate substances against their concentration gradients.

Bulk Transport

  • Involves the movement of cell membranes to transport large molecules.
  • Includes endocytosis and exocytosis.

Endocytosis

  • Material enters the cell via infolding/pockets of the cell membrane, forming vesicles/vacuoles.
  • Used to transport large molecules and even entire cells.

Photocytosis

  • Extensions of cytoplasm surround a particle, packaging it into a food vacuole.
  • Requires significant energy.

Exocytosis

  • Releases large amounts of material as vesicles/vacuoles fuse with the cell membrane.
  • Example: Water removal using contractile vacuoles.

Cells: Unicellular Organisms

  • Must maintain homeostasis, grow, respond to the environment, transform energy, and reproduce.
  • Includes some prokaryotes and eukaryotes.
  • Prokaryotes are adaptable and can live in diverse environments.
  • Yeasts are common unicellular fungi that break down complex nutrients.

Multicellular Life

  • Cells are interdependent and work together via signals and specialized tasks.
  • Cell specialization maintains homeostasis.

Cell Specialization

  • Cells become specialized for various functions, such as movement, environmental response, and substance production.

Cellular Communication

  • Large organisms rely on chemical signals, transmitted through cellular junctions.
  • Signals can alter the activity of receiving cells.
  • Cellular junctions hold cells together or allow direct passage of small molecules and chemical signals.
  • Signaling molecules bind to receptors on the cell membrane or in the cytoplasm.
  • Nerve cells (neurons) rapidly transmit impulses.
  • A steady energy supply (mitochondria) is crucial for cell function; lack of energy leads to malfunction and death.