Why is water so important to living systems??? Water & Diffusion Why is water so important to living systems???

The Importance of Water http://www.youtube.com/watch?v=DAilC0sjvy0 Most life processes occur only when molecules are dissolved in water. Serves as a means of material transport Makes up 70 to 95% of most organisms

Water is polar Means that the atoms making up water share electrons in a covalent bond but share them unequally Each molecule has a positive end and a negative end Water molecules attract each other as well as ions and other polar molecules Water dissolves many ionic compounds It is an excellent solvent

Hydrogen Bonds It is a weak bond Helps hold large molecules together

Results of polarity Capillary action and Surface tension of water help it get from soil to the tops of tall trees

Resists Temperature Change Acts as an insulator, helping maintain a steady environment Since cells exist in a mostly water environment this helps cellular homeostasis

Expands when it freezes Ice is less dense than water Causes rocks to form cracks over time by freezing and thawing

Diffusion Kinetic energy- energy of motion Brownian Motion- random motion of molecules C:\Users\nsanders\Desktop\Google Chrome.lnk

Process Diffusion is the movement of particles from areas of greater concentration to areas of lower concentration Caused by the random movement of molecules The more concentrated the substance, the more rapid is the rate of diffusion Increasing the temperature also increase the rate

Results of Diffusion Diffusion occurs until dynamic equilibrium is reached There is continuous movement of molecules but no overall concentration change

Living Systems Molecules in cells are in a water solution Difference in concentration of substances across a space is a concentration gradient Diffusion moves substances from high to low concentrations Diffusion moves with the gradient and continues until dynamic equilibrium is reached OSMOSIS IS THE DIFFUSION OF WATER ACROSS A SELECTIVELY PERMEABLE MEMBRANE!