Lecture 6 - Lipids and membranes

CHM 230 – Lecture 6: Lipids and Membranes

J. Membrane Proteins

• Functions of Membrane Proteins

  • Membrane proteins serve various important functions in biological systems, including:

    • Transport: Facilitating the movement of substances across the membrane.

    • Communication: Involved in signaling and communication between cells.

Transport Across Membranes

• Diffusion of Small Molecules

  • Small, uncharged molecules (e.g., O2, H2O) can easily diffuse through biological membranes due to their size and lack of charge.

• Transport of Larger or Charged Molecules

  • The movement of larger or charged molecules across a biological membrane is not as straightforward and requires the assistance of transport proteins.

    • These can be specific channels or carriers that facilitate movement.

• Concentration/Charge Gradient

  • Molecules naturally move down their concentration or charge gradient, which means they move from areas of higher concentration to areas of lower concentration without energy input.

• Active Transport

  • In cases where molecules must be moved against their gradient (from low to high concentration), energy input is necessary.

  • This process requires specific proteins known as pumps, which utilize energy (often from ATP) to transport substances across the membrane.

Summary of Transport Mechanisms

• Types of Transport

  • Non-mediated Transport:

    • Occurs with substances that can move freely across the membrane (e.g., O2, H2O).

  • Mediated Transport:

    • Involves the use of specific proteins to assist movement (e.g., glucose transport).

  • Active Transport:

    • Engages energy to move molecules against their concentration gradient (e.g., Na+ transport).