1. Chemistry of Life
Unit 2 – Biology I

2. 2.1 Atoms, Ions, and Molecules
All living things are based on atoms and their interactions.
All organisms depend on many chemicals and chemical reaction…. Because of this, the study of living things also involves the study of chemistry.

3. Atom: The smallest basic unit of matter.
Element: One particular type of atom.
Of the 91 naturally occurring elements, only 25 are found in organisms …. Just 4 make up 96% of the human body.
Compound: Where atoms of elements are linked, or bonded, to other atoms.

4. Chemistry Basics
Compounds properties are often different from the properties of the elements that make up the compound.
Example: Water…. Hydrogen and oxygen are both gases in nature…. Together they are a liquid.
Example: A diamond is pure carbon, but carbon is also make up sugars, proteins, and millions of other compounds.

5. Chemistry Basics
Ions: An atoms that has gained or lost one or more electrons.
Ions form ionic bonds where one atom “gives” electron(s) to another
Example NaCl (salt)

6. Chemistry Basics Covalent Bonds: Form when atoms “share” electrons.
Usually very strong bonds.
Example: Carbon dioxide (CO2)

7. Water
Properties of WATER. Water’s unique properties allow life to exist on Earth
Life depends on hydrogen bonds in water.
Your cells are mostly water. Water gives cells structure and transports materials within organism.
All processes necessary for life take place with water.

8. Water Many compounds dissolve in water.
Molecules and ions cannot take part in chemical processes inside cells unless they dissolve in water.
Important materials (sugars and oxygen) can not be transported within organisms unless dissolved in blood, plant sap, or other water based fluids.

9. Water
Some compounds form acids or bases when they break up into ions when dissolved in water.
Acids: A compound that releases hydrogen ions into a solution when dissolved.
Bases: Compounds that remove hydrogen ions from solution.
pH: A way of measuring the concentration of hydrogen ions in a solution. Range 0-14 (from acidic to basic)

10. Water
Homeostasis: Regulation and maintenance of constant internal conditions in an organism.
Most organisms need to keep their pH within a very narrow range, around neutral (pH 7.0)
Different organisms need different ranges.
Water helps ensure this homeostasis is maintained.