BIO 2.0 Cell Membrane Inner/Function Location

Phospholipid bilayer

• Location & Shape: Forms the entire cell membrane as two thin layers of phospholipids. The heads face the watery outside and inside of the cell, while the tails point toward the center.

• Function: Forms the main barrier of the cell and controls what enters and leaves.

Hydrophilic heads

• Location & Shape: Round/bulb-shaped heads located on the outer and inner surfaces of the membrane, facing the watery environments.

• Function: Interact with water and help form the membrane's outer surfaces.

Hydrophobic tails

• Location & Shape: Two thin fatty-acid tails extending inward from each head and facing each other in the center of the membrane.

• Function: Avoid water and form the membrane's water-resistant interior.

Cholesterol

• Location & Shape: Small molecules located between the phospholipid tails in the middle of the membrane.

• Function: Stabilizes the membrane and helps regulate membrane fluidity.

Integral proteins

• Location & Shape: Large proteins embedded within the phospholipid bilayer; some extend completely across the membrane like channels.

• Function: Transport substances, receive signals, and perform other membrane activities.

Peripheral proteins

• Location & Shape: Smaller proteins attached to the inner or outer surface of the membrane; they do not pass through the bilayer.

• Function: Help with cell signaling, support, and connections to other proteins.

Cytoskeleton

• Location & Shape: A network of thin protein fibers located along the inside/cytoplasmic side of the membrane and extending throughout the cytoplasm.

• Function: Maintains cell shape, provides support, and helps move/organize materials inside the cell.

ORGANZATRION

• Heads → outside edges

• Tails → middle

• Cholesterol → between tails

• Integral protein → inside/through membrane

• Peripheral protein → surface

• Cytoskeleton → just inside membrane

Main functions of Plasma Membrane

• Separates the cell from its external environment

  • Creates a boundary between the inside and outside of the cell.

• Controls what enters and leaves the cell

  • The membrane is selectively permeable.

  • Some substances can cross easily.

  • Others require proteins or cannot cross.

• Maintains the cell’s internal environment

  • Helps maintain appropriate concentrations of ions, nutrients, water, and other substances.

• Cell communication

  • Membrane proteins can act as receptors.

  • Receptors allow cells to receive signals from other cells or from the environment.

• Cell recognition

  • Membrane carbohydrates and proteins help cells identify one another.

• Cell adhesion

  • Membrane proteins help cells attach to other cells or structures.

• Provides structural support

  • Proteins in the membrane interact with the cytoskeleton.

 Selective permeability

The membrane allows some substances to cross more easily than others.