Chapter 2 Biochemistry Basic Chemistry and Water Chemistry

Basic Chemistry – Matter, Elements, and Compounds n MATTER: anything that takes up space and has mass. n ELEMENT: a substance that cannot be broken down by ordinary means. The material making up matter. n There are 92 naturally occurring elements, of these 25 are essential to life. 4 of these make up 96% of living matter (Carbon, Hydrogen, Oxygen, and Nitrogen).

n Small units of matter are called atoms. n Protons(+), neutrons(0), and electrons(-), are the subunits of atoms. n Protons = Atomic Number n Electrons = Atomic Number unless there is a charge. n Neutrons = Atomic Mass (larger number) – Atomic number (smaller number)

n COMPOUND: more than one element (more n n n than one capital letter). Formula EX: H 2 O or C 6 H 12 O 6 ISOTOPES: Different atomic forms caused by varying the number of neutrons. Example: Normal carbon is C-12, carbon isotope is C-14. The number is the mass of the isotope. Some isotopes are radioactive, they undergo a transformation to gain a stable condition. This transformation is called the half-life of the isotope. Protons and Neutrons make up the nucleus of the atom. Electrons orbit the nucleus.

Chemical Bonds n Covalent Bond: These bonds are the strongest of the bonds. They are formed by the sharing of the valence electrons.

n Ionic Bond: These bonds are formed by the taking of electrons. Anion: negative ion, Cland (OH) Cation: positive ion, Na+ and (NH 4)+.

n Hydrogen Bond: This bond is formed when hydrogen that is covalently bonded to an electronegative atom is attracted to another electronegative atom on another molecule.

Chemical Reactions n The combination of 2 or more elements forming a different product or products. Each reaction contains reactants and products. The reactants are written on the left side of the equation, while the products are written on the right side. n The reactants and products must contain the same number of atoms making the reaction balanced. n Example: n

Water Chemistry n Water is important to life. n Because of the unique properties of water, life exists in its present form on this planet. n Due to the polar covalent bonds that hold a water molecule together, hydrogen bonds form where the negatively charged Oxygen and the positively charged Hydrogen are located.

The results of these bonds are as follows (10): n 1. Cohesion: is the sticking together of similar molecules. Water is very cohesive. This allows water to be pulled along a pathway with relative ease.

n 2. Surface Tension: cohesion allows water to pull together and form droplets or form an interface between it and other surfaces. The measure of how hard it is to break this interface is its surface tension. n Water allows materials to rest upon it if the surface tension is not broken.

n 3. Adhesion: The sticking of one substance to another. Water is a good adhesive. It will cling on to many objects and act as a glue. n Capillary Action is an example of cohesion and adhesion working together to move water up a thin tube.

n 4. High Specific Heat: Specific heat of a substance is the heat needed (gained or lost) to change the temperature of 1 g. of a substance 1 degree Celsius. n 5. High Heat of Vaporization: Water must absorb a certain amount of additional heat to change from a liquid into a gas. This extra heat is called heat of vaporization.

n 6. Freezing and Expansion of Water: Water is most dense at 4 degrees C. At 0 degrees C. it is 10% less dense. Ice floats because maximum Hydrogen bonding occurs at 0 degrees C. n Ice (solid water) is less dense than liquid water, so ice floats, preventing lakes and oceans from freezing solid. The ice at the top of the water insulates the liquid below.

n 7. Versatile Solvent: Water is a major solvent in nature. When water and another substance is mixed the resulting solution is called an aqueous solution. n Any solution contains the following parts: Solute (what's being dissolved) + Solvent ( what is doing the dissolving) = Solution.

n 8. Diffusion : Occurs in cells when substances (oxygen, carbon dioxide, salts, sugars, amino acids) which are dissolved in water move from an area of higher concentration to an area of lower concentration.

n 9. Osmosis: The movement of water molecules through a semi-permeable membrane from an area of greater water concentration to an area of lesser water concentration.

n n 10. p. H: Refers to the dissociation of water molecules. p. H Scale: n n n The p. H scale goes from 0 14. The p. H of pure water is 7 (neutral) Substances added to water can lower or raise the p. H. A solution with a p. H below 7 is acidic. A solution with a p. H above 7 is basic (alkaline)

n Buffers: A buffer is a mixture of chemicals that keeps the p. H of a solution relatively constant. A buffer system acts by taking up or releasing H ions. They add H ions when a solution becomes basic (higher than 7) and they take H ions out of the solution when the p. H becomes acidic (lower than 7).