Active Transport and Cell Membrane Notes

Active Transport

  • Membrane proteins facilitate nutrient and waste transport.
  • Passive transport moves solutes along the concentration gradient (high to low concentration).
  • Active transport is required when a cell needs to move solutes against the concentration gradient (low to high concentration).
  • Active transport requires energy and uses membrane proteins.

ATP -> ADP + P Active Transport

  • Active transport uses energy to move solutes against their concentration gradients through transport proteins.

  • The energy source is often ATP.

  • Active transport proteins can move one or two solutes in the same or opposite directions.

The Sodium-Potassium Pump

  • The sodium-potassium pump is found in animal cell plasma membranes.
  • It uses ATP to pump sodium and potassium in opposite directions against their concentration gradients.

Comparing Facilitated Diffusion and Active Transport

  • Facilitated Diffusion: moves molecules along the concentration gradient (high to low concentration).
  • Active Transport: Moves molecules against the concentration gradient (low to high concentration) and requires energy.

Cell Membrane

  • The cell membrane consists of proteins, cholesterol, glycoproteins, and glycolipids.

Proteins in the Cell Membrane

  • Peripheral proteins are anchored on one side of the membrane.
  • Integral proteins are embedded in the membrane.
  • Transmembrane proteins are integral proteins that span the entire bilayer.

Cholesterol in the Cell Membrane

  • Cholesterol affects membrane flexibility in a temperature-dependent manner.

Glycoproteins and Glycolipids in the Cell Membrane

  • Glycoproteins and glycolipids have sugar chains extending out of the cell.
  • They are used for communication with other cells.

Glycolipids and Glycoproteins in the Cell Membrane

  • Cells respond to the environment through interactions between glycolipids/glycoproteins and other molecules.

Fluid Mosaic

  • The plasma membrane is described as a fluid mosaic.
  • Phospholipids flow sideways within the membrane.

Fluid Mosaic

  • Proteins are like mosaic tiles in a fluid sea of lipids.
  • Proteins can move within the membrane and form connections with structures inside and outside the cell.

Membrane Protein Functions

  • In addition to transport, proteins have several functions:
    • Defense: Antibodies and receptors activate cells against pathogens.
    • Signal transduction: Receptor proteins receive signals, triggering cellular activities.

Membrane Protein Functions

  • Additional functions of membrane proteins:
    • Cell-cell recognition: Glycoproteins bind to other cells for communication.
    • Enzymatic activity: Peripheral proteins carry out biochemical reactions.
    • Cell-cell adhesion: Connections between the cytoskeleton and extracellular matrix form tissues.