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Glossary of AP Biology Chapter 2

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List the levels of organization
Atom, molecule, organelle, cell, tissue, organ, organ system, organism, population, community, ecosystem, biosphere
Atom
Smallest unit of matter that still retains the properties of an element
Element
Substance that cannot be broken down
Molecule
A group of two or more atoms with covalent bonds
Compound
Ex: proteins. Substance containing two or more elements in a fixed ratio.
Four chemicals most abundant in living matter
Oxygen, carbon, hydrogen, nitrogen
Other chemicals needed by the body
Calcium and phosphorus, idodine (in trace amounts), fluoride.
proton
Subatomic particle with a single positive electrical charge
Electron
Subatomic particle with a single negative charge
Neutron
electrically neutral subatomic particle
Nucleus
Atom's central core, contains protons and neutrons
Atomic number
Number of protons in element
Mass number
Protons plus neutrons
Isotopes
Same element, different mass number. Example: carbon-13 and Carbon-12
radioactive isotope
Nucleus decays spontaneously.
Importance of radioactive isotopes
Tracers for monitoring the fate of atoms in living organisms; studying photosysthesis; diagnose kidney disporders; indicate cancer.
Electron shell information
The farther an electron is from the nucleus, the greater its energy. Atoms whose outer shell is not full tend to participate in chemical reactions
What is an ionic bond? Give an example.
Two opposite charges (stealing electrons). NaCl. Sodium chloride is called a salt because it exists as a crystal
What is a covalent bond? Give an example
Two nonmetals bonding. Atoms share one or more pairs of outer shell electrons. O2.
What is the difference between double, single, and triple covalent bonds?
The number of shared pairs of electrons.
Electronegativity
An atom's attraction for its electrons. The more electronegative an atom, the more strongly is pulls shared electrons to its nucleus.
Difference in polar and nonpolar covalent bonds
Nonpolar covalent bonds share electrons equally. Polar do not. Water is polar.
Why is ice less dense than water?
because as it freezes the hydrogen bonds are stable and each water molecule forms H bonds with 4 neighbors at 'arm's length' creating a crystal. In liquid H2O, hydrogen bonds are constantly broken and re-formed.
Why is water a great solvent?
Because of the polarity of its molecules
Definition of Acid
Donates hydrogen ions to solution
Definition of Base
Accepts hydrogen ions and removes from solution
What does each number represent on the pH scale as you go up?
Each unit represents a tenfold change in the concentration of hydrogen ions in solution.
What are buffers?
buffers resist changes in pH by accepting Hydrogen when it is in excess and donating it when it is depleted.
Why does acid precipitation occur?
Results mainly from the presence of sulfur oxides and nitrogen oxides. The oxides react with water vapor in air to form sulfuric acid and nitric acid.
What is a chemical reaction?
A process leading to changes in the composition of matter. Reactants yield products.

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