1. Essential Chemistry for Biology
Campbell Chapter 2

2. Some definitions Matter: anything that occupies space and has mass
Three phases: solids, liquids, gases
Chemical element: a substance that cannot be broken down into other substances by chemical reactions
92 naturally occurring elements on Earth;
Listed on the periodic table
25 are essential for life
CHOPKINS CaFe

3. Atoms
Atoms: the smallest unit of matter that still retains the properties of an element.
Protons: Positively charged, in the nucleus
Neutrons: Electically neutral, in the nucleus
Electrons: negative charge, orbiting the nucleus
Multiple layers
Outer shell electrons
Atomic Number: the number of protons in an atom
Defines an element; all atoms of any element have the same number of protons
1 = hydrogen; 2= helium, 6= carbon, etc
Atomic Mass/Mass Number:
the number of protons + neutrons
Ions: unequal numbers of protons and electons
Cations: lose an electon
Anions: gain an electron
Chemical bonds

4. Molecules Molecules: combinations of two or more atoms
Compounds: substances that contain two or more elements in a fixed ratio
Water: H20
Salt NaCl
Trace elements: required in only very small amounts and essential for life
Iodine: goiter
Isotopes: different forms of atoms of a single element
Defines the isotope: C12, C13, C14
Radioactive isotopes are unstable and decay, emitting energy

5. Chemical Bonds Hold atoms close together in a molecule Three types:
Based on sharing electons in the outer shell
Three types:
Covalent: equal sharing
Ionic: absolute transfer from one atom to another
Polar bonds: unequal sharing of electrons between atoms in a molecule
Molecules can be held together in a substance
Hydrogen bonds: weak attractions resulting from uneven distribution of electrons in a molecule
Chemical reactions involve making or breaking bonds
Molecules can be formed or destroyed
They can be moved together (condensation) or apart (evaporation)

6. Chemical Reactions Rearrangement of atoms among molecules
Breaking apart: catabolism
Joining together: anabolism
Exchanging
Chemical Equations
reactants, the starting materials, and
products, the end materials
Usually include information abut the state (solid, liquid, gas, solution)
Balanced: # of atoms of each element is the same on each side of the equation
2 H2 (g) + O2 (g)  2 H2O (l)

7. Water: More Precious than Gold
Life began and evolved in water
Cells = 70-95% water
Water is the universal solvent of living things
Most biomolecules dissolve in water
Polarity of water molecules means that water dissolves a wide range of biological compounds
Heat capacity regulates internal temperature
Evaporative cooling occurs when a substance evaporates and the surface of the liquid remaining behind cools down.

8. Properties of Water
Polarity leads to surface tension, the difficulty of breaking or stretching the surface of a water droplet
essential for transport within plant tissues
high heat capacity: water resists changes in temperature
Heat: the amount of energy associated with the movement of the atoms and molecules in a body of matter
Resists evaporation and freezing
extends the liquid phase through a wide temperature range

9. Acids and Bases
Solution: a liquid consisting of a homogeneous mixture of two or more substances
Solvent: The dissolving agent
Solute: The dissolved substance
Syrup: sugar dissolved in water
Acid: molecule with a hydrogen atom that it can shed
HCl(aq)  H+(aq) + Cl-(aq)
HCOOH(aq)  H+(aq) + COOH-(aq)
Base: molecule which can accept a hydrogen atom
NH3(aq) + H2O  NH4+(aq) + OH-(aq)

10. Buffers
Aqueous solutions allow solutes to gain or lose their hydrogen ions more easily by stabilizing the products
Vinegar is acetic acid: CH2COOH
In pure form it is a neutral molecule: CH2COOH(l)
In aqueous solution it can dissociate into a hydrogen ion and an acetate ion
H+(aq) and CH2COO-(aq)
Buffers: substances that resist pH change
Biological liquids contain dissolved salts that act as buffers
Living things exist within a narrow range of acidity

11. Biology and Society Drought severe crop damage,
shortages of drinking water,
dust storms,
famine,
habitat loss, and
mass migration

12. Biology and Society: Ocean Acidification
Increases in atmospheric CO2 concentrations may lead to
the acidification of the oceans
Gas phase carbon dioxide will dissolve in ocean water
CO2(aq) + H2O  H+(aq) + HCO3-(aq)
ecological disasters
Coral reef death

13. Life cannot exist without water
If life similar to ours has evolved elsewhere in the universe, then it too would depend upon water
Researchers at NASA missions have found evidence that water was once abundant on Mars
Microbial life may exist below the Martian surface