Movement across the Cell Membrane Section 7-3

Cell Membrane Cell Membrane

Passive Transport Passive Transport  Movement across the cell membrane that takes no energy to be done.

Diffusion Diffusion  Movement of substances from an area of high concentration to low concentration.

Concentration Concentration  Solute vs. Solvent Water: 93%: Solvent Sugar: 7%: Solute We have a 7% sugar solution.

Example of Sugar in Water  Inside the Cell  7% Glucose  ________________________  Outside the Cell  3% Glucose

Osmosis Osmosis  Movement of water across the cell membrane.

Example with Water Example with Water  Inside the Cell  98% water  ______________________  Outside the Cell  96% water

Hypertonic:  The solution has a higher concentration of solute (= lower solvent-liquid) when compared to another solution. Hypotonic:  The solution has a lower concentration of solute (= higher solvent-liquid ) when compared to another solution. Isotonic:  The solutions have the same concentration of solute. Different Solutions Bozeman Cell Membrane Video Clip Different Solutions Bozeman Cell Membrane Video Clip Bozeman Cell Membrane Video Clip Bozeman Cell Membrane Video Clip

Isotonic Solution Isotonic Solution  Inside the Cell  93% Water-7% Salt  ______________________  Outside the Cell  93% Water-7% Salt

Hypertonic vs. Hypotonic  Inside the Cell  92% Water-8% Salt  ______________________  Outside the Cell  95% Water-5% Salt

Hypertonic vs. Hypotonic  Inside the Cell  98% Water-2% Salt  _____________________  Outside the Cell  94% Water-6% Salt

Osmosis: Movement of water molecules (blue circles) through a cell membrane (red) from a region of high (water) concentration (inside cell) to a region of lower (water) concentration (outside cell). Inside the cell the solution is hypotonic with a low solute (salt) concentration. Outside the membrane the solution is hypertonic with a high solute (salt ion) concentration shown by the orange circles. The membrane is not permeable to the salt ions. Since the concentration of water molecules per unit area is higher inside the cell than outside, water moves out of the cell. Diagram Of Osmosis Through A Cell Membrane

The internal body fluids of a marine fish are hypotonic compared with the hypertonic sea water; therefore, water molecules diffuse out of the fish through the gill region. To cope with this steady loss of water, the marine fish has greatly reduced urine with little or no water loss, continuously drinks water, and excretes excess salt through the gills by active transport. Conversely, a freshwater fish is hypertonic compared with the water of a lake or pond; therefore, it continually absorbs water through the gill region. To cope with this steady influx of water molecules, the freshwater fish has copious urine, drinks very little water, and absorbs salts through the gills by active transport..