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Terms

  • Blocks

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Original Cell Membranes

  • Functions of Cell Membranes

    • 1. Separate the intracellular components from the external environment.

    • 2. Control of the internal conditions within the cell as well as the maintenance of homeostasis.

Two Key Qualities of Cell Membranes

  1. Semi-permeability

    • Definition: Only certain materials are able to freely cross the cell membrane.

  2. Selectivity

    • Definition: The cell can control the passage of any material that cannot freely cross the membrane.

Cell Adhesion

  • Definition: When cells attach to other surfaces via specialized membrane proteins called cell adhesion molecules (CAMs).

  • Implications: Targeting CAMs can limit
    1) The spread of malignant cancers (by inhibiting metastasis).

Example of Cotransport

  • Cotransport Definition: The absorption of glucose in the kidneys and small intestines is an example of cotransport, where glucose is cotransported with sodium ions.

Antiport

  • Definition: Moves molecules in opposite directions.

  • Example: The Na+/K+ pump, which is used in nerve cells to establish the resting potential.

Ligand-Gated Ion Channel

  • Facts:

    1. Change their conformation in response to the binding of a ligand.

    2. In neurons, acetylcholine is a neurotransmitter released from nerve cells.

    3. Muscles contain nicotinic acetylcholine receptors that will trigger the opening of an ion channel when activated.

    4. Binding of acetylcholine to these receptors results in the influx of ions into the muscle, triggering a cascade that results in muscular contraction.

Cotransport Revisited

  • Definition: The movement of an ion along its concentration gradient to the movement of a solute against its concentration gradient (secondary active transport).