The Chemical Basis of Life Chapter 4 The Chemical Basis of Life

What are we? (all living things)? Bubbling beakers of chemical reactions, we call “LIFE”…

4.1 Life involves… A. Matter Anything that occupies space and has mass Physical “stuff” of the universe 3 states: solid, liquid, gas

4.1 Elements & Compounds… a. Elements Pure substance,simplest form Made up of 1 type of atom Ex: Hydrogen (H), oxygen (O), nitrogen (N) ~110 elements on Periodic Table

Open your Agenda…. Page 124

4.1 Elements verses Compounds… 2 or more elements Chemically combined in a fixed ratio Written as formulas Ex: water – H2O carbon dioxide – CO2 sugar –C6H12O6

4.1 Elements used to make the compounds found in the human body Chemical Symbol Mass (70Kg person) O 43 Kg C 16 Kg H 7 Kg N 1.8 Kg Ca 1 Kg P 780 g K 140 g S 80 g Trace elements make up <0.01% of your body

Important Elements in Life…. C HOPKINS CaFe Mg NaCl (What elements are represented here?)

The Most abundant elements in Life…. What does a goose say??? HONC (What elements are represented here?)

Now then. What are atoms? Basic building blocks of matter A desk, the air, & you are made up of atoms!

What everything is made of: basic structure Electron shell

4.2 Atoms are made out of 3 basic particles… Electrons Negative charge, no mass

within the nucleus… Proton – positively charged Neutron – no charge (neutal) Mass of each is equal. Together, give matter its mass (weight)

To make living things, we bond atoms into molecules 2 types of bonds that hold atoms together: Covalent Ionic

4.3 Covalent Bond A bond formed when 2 atoms share electrons Molecules form when 2 or more atoms are connected by covalent bonds

4.3 Ionic Bond A bond formed when an electron is transferred from 1 atom to another (one atom gains an electron; another atom loses it. Atoms become + or - ions

An ionic bond forming by transferring an e- from Na to Cl

Molecular structure is shown as a ‘molecular or structural formula’… Molecular: shows the kind of and the number of atoms Structural: shows the arrangement of atoms in a compound (the bonds)

Molecular formula of water H2O Structural formula of water

Molecular formula of glucose C6H12O6

Structural formula of glucose

4.3 Chemical Equations Represent a chemical reaction Ex. 2 H2 + O2  2 H2O

4.3 Reactants & Products Reactants = the chemicals on the LEFT side of the equation  Products = the chemicals on the RIGHT side of the equation (are made or produced in the reaction)

Balanced equations 2 H2 + O2  2H2O

4.3 Balanced Equation Example H2 + O2  H2O is unbalanced Why?

4.3 Balanced Equations To BALANCE equations, add COEFFICIENTS in front of the compounds (go back and balance w/ coefficients)

4.4 Why Life depends on water

1. Because H2O molecules are POLAR, they are weakly bonded together

This attraction = ‘Cohesion’; molecules of the same kind “stick” to one another Adhesion – attraction between unlike molecules Trees depend on these forces!! How??

2. Water is a solvent Ex. Dissolving salt into water Other substances dissolve in water. They will not separate out Ex. Dissolving salt into water

4.4 solutions contain: 1. The solvent – liquid that other substances are dissolved in. is The 1 in greater quantity (ex, Water , the “universal solvent”, because so many things disslove in it) 2. And the solute(s) – substances dissolved . Present in lesser amounts Ex. salt

When water is the solvent it forms an aqueous solution

__________________________________________________________________ Notes, p4: The pH Scale measures the concentration of hydrogen ions (H+) in an aqueous solution. It ranges from 0 to 14. Neutral __________________________________________________________________ 0 Acids 7 Bases 14

Acids have more H+ than pure H2O Acids measure less than 7 on the pH scale Examples: HCl (hydrochloric acid) Vinegar (acetic acid) Lemon juice (citric acid)

Bases have less H+ than pure H2O pH value is alwaysgreater than 7 Examples: NaOH (sodium hydroxide) KOH (potassium hydroxide) NH3 (ammonia)

Neutral Substances have a pH = 7

Buffers… Causes a solution to resist change in pH by adding or removing H+’s Many biological fluids contain buffers!! Why??

4.4 Indicators… Chemicals that turn different colors in different pH values Bromothymol Blue, Phenolphthalein, pH paper Turn to page 8 of your packet