Cellular Transport

HOMEOSTASIS THE PROCESS OF MAINTAINING A CONSTANT INTERNAL ENVIRONMENT DESPITE CHANGING EXTERNAL CONDITIONS

Figure 7-15 The Structure of the Cell Membrane Section 7-3 Outside of cell Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains Inside of cell (cytoplasm) Go to Section:

CELL MEMBRANE IS SELECITVELY PERMEABLE DIFFUSION OF MOLECULES OCCURS ACROSS THE CELL MEMBRANE

Movement through the Membrane Diffusion Osmosis Passive Transport Facilitated Diffusion Active Transport

PASSIVE TRANSPORT MOVEMENT OF MOLECULES FROM AN AREA OF HIGHER CONCENTRATON TO AN AREA OF LOWER CONCENTRATION KINDS: DIFFUSION OSMOSIS FACILITATED DIFFUSION DOES NOT REQUIRE THE USE OF ENERGY

DIFFUSION TERMS EQUILIBRIUM: CONCENTRATION GRADIENT: exists when particles are in higher concentration in one area and lower in concentration in another. Causes movement of the molecules EQUILIBRIUM: when the rate of particle spreading is even throughout a given area.

Osmosis THE DIFFUSION OF WATER MOLECULES FROM AN AREA OF HIGHER CONCENTRATION TO AN AREA OF LOWER CONCENTRATION THROUGH A SELECTIVELY PERMEABLE LIPID BILAYER MEMBRANE WITHOUT ENERGY When the transfer of water molecules into and out of the cell reaches the same rate, a state of equilibrium is reached.

Figure 7-17 Osmosis Cell membrane Section 7-3 Water molecules Higher Concentration of Water Cell membrane Lower Concentration of Water Sugar molecules Go to Section:

3 Osmotic Solutions Hypertonic Hypotonic Isotonic

Hypertonic Cell shrinks, because water moves out of cell, because there’s more water in cell than in solution. Salt water: 30% salt, 70% pure water Cell: 80% water start end

Hypotonic Cell swells (can burst), because water moves into cell, because there’s more water outside cell than in solution Water: 100% pure water Cell: 80% water start end

Water Water Hypertonic Isotonic Hypotonic

PROTEIN CHANNELS PROVIDE OPENINGS THROUGH WHICH SPECIFIC SUBSTANCES CAN DIFFUSE ACROSS THE MEMBRANE THESE PROTEINS ARE SELECTIVE A PROTEIN CHANNEL EMBEDDED IN THE MEMBRANE PROVIDES A DIRECT PATH FOR A CHEMICAL TO PASS DOWN ITS CONCENTRATION GRADIENT, SO IT REQUIRES NO ENERGY

Facilitated Diffusion Section 7-3 Glucose molecules High Concentration Cell Membrane Protein channel Low Concentration Go to Section:

Active Transport movement from an area of lower concentration to an area of higher concentration against the concentration gradient using energy Endocytosis – taking in materials by forming pockets Phagocytosis – taking in large particles Pinocytosis – taking in liquid/fluids Exocytosis – removing materials by fusing vacuoles