Ch. 5 – Homeostasis & Transport What is homeostasis? It is the biological balance of relationship between an organism’s cell and its environment. Homeostasis is maintained by the movement of molecules in and out of the cell. All organisms must maintain homeostasis.

What is diffusion? The movement of molecules from an area of greater concentration to an area of lesser concentration. (pg. 224) What is the open space in which the molecules of a substance diffuses? Concentration gradient Once the molecules are distributed equally in an area, then an equilibrium is established.

Cell Membrane What is a permeable membrane? It is where substances pass through the membrane. So, what is an impermeable membrane? A membrane that does not allow a substance to pass through its membrane. Define a semi-permeable membrane. A membrane that only allows certain molecules through the membrane.

Osmosis Define osmosis. It is the diffusion of water from an area of high concentration to an area of low concentration, through a membrane. What is it called when the concentration of a solution of molecules is higher outside the cell than what is inside the cell? Hypertonic

What would you call a cell in which the concentration of molecules is lower outside the cell, than the concentration of molecules inside the cell? Hypotonic This term means the conc. of solutes inside and outside the cell are equal. Isotonic Pg. 97

Turgor Pressure Turgor pressure is the water pressure inside the cell. The condition in which the turgor pressure is lost by water leaving the cell is called plasmolysis. Ex. Plants wilting If a cell’s turgor pressure is so much that the cell bursts this is called cytolysis. Ex. Plants freezing

Homeostasis in Cells Passive transport or facilitated diffusion- is the movement of any substance through a membrane without chemical energy needed. This does not require a live cell. Ex. Plant’s roots absorb water Active transport requires chemical energy to pass a substance through a membrane. This requires a living cell Ex. Na absorbed from a cell

Endocytosis- is the process that engulfs substances too large to pass into a cell membrane. 2 TYPES 1. Pinocytosis-is the movement of fluids into the cell. 2. Phagocytosis- is the movement of large food particles engulfed into the cell. Exocytosis- is the process that passes large molecules outside of a cell.