BIOL 231 Unit 1 Chap 3: Chemical Levels of Organization

elements

fundamental forms of matter, 92 naturally occur on earth

atom

smallest part of an element

atomic number

number of protons

atomic mass

number of protons + number of neutrons

What determines if atoms will interact?

number + arrangement of their electrons

electrons

carry a negative charge, attracted to protons in the nucleus, contained in energy levels/shells, enable atoms to interact/form bonds

energy levels

atoms differ in the number of occupied shells

lower energy shell

closer to nucleus, filled first

outer shells filled

electrons do not form bonds/react

first electron shell

up to 2 electrons

second + third electron shells

up to 8 electrons

electron vacancies

unfilled shells make atoms more likely to react and form bonds

bond

union between electron structures of atoms

molecules

contain atoms of only one element

compounds

contain more than one element

ionic bonding

exchanges electrons

covalent bonds

sharing of electrons, atoms share a pair or pairs of electrons to fill the outermost shell, number of electron vacancies determine the number of bonds formed

nonpolar covalent bonds

atoms share electrons equally

polar covalent bonds

electrons spend more time near the nucleus with the most protons, makes a charged compound

hydrogen bonding

atom in one polar covalent molecule is attracted to an oppositely charged molecule

synthesis reaction

builds complex organic compounds from similar subunits - requires energy

decomposition reaction

breaks down complex organic compounds into smaller subunits - releases energy

carbohydrates

monosaccharides and polysaccharides

lipids

triglycerides and phospholipids

proteins

amino acids and polypeptide

nucleic acids

nucleotides, DNA, RNA, and ATP