8.1 CELLULAR TRANSPORT MRS. KREITNER’S BIOLOGY CLASS

DIFFUSION Definition: The net movement of particles from an area where there are more particles of the substance to an area where there are fewer particles. Doesn’t require additional energy because the particles are already in motion. Diffusion continues until the concentration are the same in all areas of the water. Dynamic Equilibrium: The particles continue to move randomly, but the overall concentration doesn’t change.

WHAT AFFECTS THE RATE OF DIFFUSION? 1.Concentration 2.Temperature 3.Pressure When these three are in high amounts diffusion occurs more quickly because the particles collide more often. 4. Size and 5. Charge of a substance also affects the rate of diffusion.

FACILITATED DIFFUSION Ions and molecules that cells need to function can’t diffuse across the plasma membrane. Facilitated diffusion uses transport proteins to help move some ions and small molecules across the plasma membrane. No additional energy is required because particles are already moving.  Because no energy is added, it is referred to as passive transport.

OSMOSIS: DIFFUSION OF WATER Unlimited diffusion through the plasma membrane. Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis in the cell. What controls osmosis?  The concentration of water soluble molecules in a solution.

OSMOSIS DIAGRAM

ISOTONIC SOLUTION In an isotonic solution the concentration of dissolved substances in the solution are the same as the concentration of the dissolved substances inside the cell. Iso = Equal Doesn’t experience osmosis and cells retain their normal shape.

HYPOTONIC SOLUTION The concentration of dissolved substances is lower in the solution outside the cell than the concentration inside the cell. More water outside the cell than inside. Hypo = Hippo: The cell Swells and could burst (only animal cell) Experiencing Osmosis as water moves into the cell. FYI: Grocers use this type of solution on their produce to help keep it looking fresh.

HYPERTONIC SOLUTION The concentration of dissolved substances outside the cell is higher than the concentration inside the cell. Experience osmosis as the water flows out of the cell. Animal Cells shrivel, Plant Cells Wilt

ANIMAL AND PLANT CELLS

ACTIVE TRANSPORT The movement AGAINST the normal flow/concentration gradient.  Moving particles from a region of lower concentration to a region of higher concentration. Requires energy to counteract the force of diffusion.

HOW ACTIVE TRANSPORT OCCURS 1.A carrier protein first binds with a particle of the substance to be transported. * Each type of carrier protein has a shape that fits a specific molecule or ion. 2.When the proper molecule binds with the protein, chemical energy allows the cell to change the shape of the carrier protein so that the particle to be moved is released on the other side. (Like opening a Door) 3.When the particle is released, the protein’s original shape is restored.

TRANSPORT OF LARGE PARTICLES Some cells can take in large molecules, groups of molecules, or even whole cells. Requires Energy, so Active Transport Endocytosis  Endo = within  Process by which a cell surrounds and takes in materials from its environment.  Material gets a “bubble” of plasma membrane, aka a Vacuole with its contents. Exocytosis  Exo = Out  The expulsion or secretion of material from a cell.  Cell uses it to expel wastes, secrete hormones.

And now it’s time for some Educational Movies!