Cell Membrane Transport Flashcards

Cell Membrane Structure

• The cell membrane is the outer boundary of a cell.
• It's a phospholipid bilayer with embedded proteins and other molecules.
• Selectively permeable, controlling substance passage.

Cell Membrane Functions

• Physical Barrier: Separates extracellular and intracellular environments.
• Passage of Materials: Regulates substance movement.
• Sensitive to Changes: Responds to changes in the extracellular fluid.
• Structure: Provides support via cytoskeleton attachment.

Diffusion

• Movement of particles from high to low concentration areas.
• Results from random molecular motion due to kinetic energy.
• Passive process (no ATP needed).

Concentration Gradient

• Substances diffuse along the concentration gradient until equilibrium is reached.

Osmosis

• Diffusion of water across a selectively permeable membrane.
• Water moves from high to low concentration.
• Passive process (no ATP needed).

Facilitated Diffusion

• Diffusion across cell membranes with the help of transport proteins.
• No energy (ATP) required.
• Examples: glucose & amino acids

Active Transport

-Requires energy – adenosine triphosphate (ATP)
-Substances move from low to high concentration (against the concentration gradient)
-Example: membrane pumps (proteins)

Membrane Transport Proteins

• Aid in substance movement across the membrane.
  • Channel proteins: open channels that ONLY allow simple diffusion
  • Carrier proteins: allow facilitated diffusion and active transport.

Membrane Transport

• Passive processes: no cellular energy required (diffusion, osmosis, facilitated diffusion).
• Active processes: require ATP (membrane pumps, exocytosis, endocytosis).

Endocytosis

• Cells absorb large particles by engulfing them with their cell membrane to form a vesicle.
  • Pinocytosis: cell drinking
  • Phagocytosis: cell eating

Exocytosis

• Things exiting the cell