“…beneath the clothes, we find a man... and beneath the man we find... his... nucleus.”-Nacho Libre Reference Text - Modern Biology Chapter / pgs

Chapter 3-1 (pgs 49-51) Biology

 The chemical reactions of all living things take place in a watery environment  Water has many unique properties that make it one of the most important compounds in living things.

unique properties Most of water’s BIOLOGICAL functions are a direct result of its molecular structure! It’s these unique properties that make water the most important and abundant compound in living things. 1. Polarity 2. Hydrogen Bonding Adhesion & Cohesion Capillarity  Temperature moderation H H O H

three A water molecule (H 2 O), is made up of three atoms - one oxygen and two hydrogen covalently bonded together. However, these atoms do not share electrons equally oxygen atom attracts more electrons.  In each water molecule, the oxygen atom attracts more than its "fair share" of electrons. oxygennegative ◦ The oxygen end “acts” negative hydrogenpositive ◦ The hydrogen end “acts” positive O H H O H

POLAR  Because of this uneven pattern of charge, water is called a POLAR molecule. gy/Biology1111/animations/dissolve.html

 Polarity  Polarity makes water very good at dissolving things (**effective solvent).  Breaking up molecules such as sugars, proteins and ionic compounds such as salt, are essential to functions in the body.

 Water forms hydrogen bonds with other water molecules. ◦ HYDROGEN BOND ◦ HYDROGEN BOND-bond between hydrogen of one molecule and the negative region of another molecule in this case, oxygen.

A picture of Hydrogen bonds!

cling to itself other surfaces. The attractive force of the hydrogen bonds gives water the properties that causes it to cling to itself and other surfaces. We call these forces: Cohesion and Adhesion

 COHESION  COHESION-the same kind of particles being attracted to each other (water sticking to other water). surface tension- ◦ Results in surface tension- a surface film on water that allows insects to walk on the surface.  ADHESION  ADHESION-water molecules and molecules of solid surfaces are attracted to each other. ◦ EXAMPLE: water sticking to plant leaf

Surface Tension…this water strider cannot generate enough force to break through the hydrogen bonds of the water molecule !

adhesion and cohesion  Together, adhesion and cohesion enable water molecules to move through narrow tubes against the force of gravity Capillarity (capillary action) Capillarity (capillary action)-the ability of water to move through fine pores or up a narrow tube against gravity due to adhesion  Example: the flow of water through a plants stem

 Water’s  Water’s ability to absorb larges amount of energy helps keep cells at an even temperature despite temperature changes in the environment.HOMEOSTASIS

 Homeostasis -  Homeostasis - Ability to maintain a steady state despite changing conditions  Water  Water is important to this process because: a. Makes a good insulator b. Resists temperature change c. Universal solvent d. Coolant e. Ice protects against temperature extremes (insulates frozen lakes)

 On a separate sheet of paper, answer the section review questions 1- 6 in your text on page 51.  All answers should be in complete sentences.