The Chemical Basis of Life. Biology. All living organisms are made up of matter ( anything that takes up space & has mass ) Matter is composed of elements (the basic substance or chemical that cannot be broken down)
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All living organisms are made up of matter (anything that takes up space & has mass)
Matteris composed of elements (the basic substance or chemical that cannot be broken down)
There are about 25 essential elements necessary for life; 4 make up 96% of the human body (in this order): O, C, H, & N
Most of the other 4%: Ca, P, K, S, Na, Cl, & Mg
Trace elementsare found in small quantitieschemical composition of living organisms
Look at your food labels. Most contain trace elements (ie. Fe, I, Cr, Co). Water is treated with F & I.
Atoms, meaning indivisible, are the smallest units of matter, contain particles:
1. Protons (p+) have a positive charge and are located within the nucleus (center) of the atom.The proton # always remains the same.
2. Neutrons (n) have a neutral or no charge and are also located within the nucleus of the atom.
Elements have a unique # of p+; this is the atomic number. Ex.) Helium (He) has the atomic # of 2 and has 2 p+; C has 6 p+ and the atomic # of 6.
Na has 1 e- in its outermost shell; Cl has 7 e- in its outermost shell. Cl is anxious to gain 1 e- to fill the octet rule while Na is more than willing to give up that 1 e- to satisfy that rule.
Ionic bondsform as the result of e- transfer; 1 element gives/donates an e- while the other element receives/accepts the e-. In this case, Na donates, Cl receives.
These bonds result in atoms (or molecules) w/ electrical charges and are a.k.a.ions.
The compounds that formed are saltswhich exist as crystals in nature and readily dissolve in water.Ionic Bonds
Covalent Bondsare strong bonds that share e-; these formmolecules.
However, most covalent bonds do not share e- equally. These are polar covalent bonds. Ex.) H2O.
Hydrogen bondsare weak bonds that are crucialto the 3D shape of large molecules (DNA & proteins).
The properties of water include:
Adhesion is the ability of one molecule to stick to something else; in this case H2O can stick to the veins or cell walls of the plant.
Adhesion & Capillary Action:
Through cohesion and adhesion, capillary action occurs.
Surface Tension is the difficulty of H2O to stretch or break; H2O has a high surface tension (difficult to break).
Can Cohesion, Adhesion, and Surface Tension occur independently? http://www.societyofrobots.com/images/robot_JB_lizard1.jpg
Water exists naturally in 3 states: as a solid, liquid and a gas (water vapor).
When water freezes, it is less dense than when it is in liquid form. Why? H Bonds!
The H Bonds stabilize & hold a crystalline pattern (at arms length). This allows ice to float on water (in the liquid state).
This is an important property b/c only the top layer of water (in a body of water) will freeze & it will not sink.
This allows life in the water environment to survive. Also, the ice insulates the water (like a blanket from the cold air).The Properties of Water, Cont’d
Water is the solvent of life; this means it can dissolve many substances (due to its polarity).
Why is this important to life?
Buffersare substances that stabilize pH.Acids and Bases, Cont’d
__H2+ __ O2 __H2O