Bio 151 chapter 2

chemical evolution

Origin of life on Earth

formation of increasingly complex compounds

4 types of atoms that make up 96% of earth

hydrogen, carbon, nitrogen, oxygen

basic atomic structure

protons +1

neutrons neutral charge

electrons -1

equal balance of protons and electrons makes a neutral charge

elements

entirely single atoms

isotopes

elements with different number of neutrons

elements will have different masses

ex: carbon-12 and carbon-13

makes up 99% of atoms in a body

carbon, hydrogen, nitrogen, phosphurus, sulfide

electrons

outer electrons shell called valence electrons

each orbital can hold up to 2 electrons

orbitals grouped togather into levels called elctron shells

smaller number of electrons are closer to the nucleus and have less energy

they stay in their own orbital

valence shell

holds valence electrons

number of unpaired valence electrons is called the varence of an atom

different atoms have different numbers of unpaired electrons

unpaired valence will react to other atoms

they are unstable

stable atoms

valence electrons shell that are full and paried

covalent bonds

form when unpaired valence electrons are with 2 atoms

2 or more connected atoms is called an molecule

compounds

molecules in which atoms of different elements are bonded together

pull shared electrons toward their nuclei with varying strengths (electronegativity)

nonpolar

covalent bonds in water molecules

Electrons are halfway between 2 atoms

shared equally

Electrons completly transferred

tranfer gives each atom a full valence shell

ionic bond

ions

atoms or molecules that carry charge

cation(ion)

atoms loses electron becomes postive

anion(ion)

atom gains electron becomes negative

polar

covalent bonds in water molecules

electrons not shared equally

partial charges exist on O and H

O has more electronegativity

Bonds strength(weakest to strongest)

non-polar (equal sharing), polar(covalent), ionic(transfer of electrons)

simple molecules

number of unpaired electrons determines number of bonds abd atom can make

water

75% of all cells

excellant solvent

solute dissolved into solvent makes a solution

substance are more likely to react when dissolved in water

water is polar

single water molecule is covelant

muitple water molecules is a hydrogen bond

oxygen atom has a partial negative charge

hydrogen has a partial postive charge

hydrophilic(water-loving molecules)

ions and polar molecules stay in solution due to their interactions with water partial charges

hydrophobic

uncharged and nonpolar compounds

do not dissolve in water

interact with other hydrophobic molecules through hydrophobic interaction

cohesion

attraction between like molecules

adhesion

attraction between unlike molecules

water is cohesive

stays togather because of hydrogen bonds

adheres to sufaces with polar or charged compounds

surface tension

cohesive force caused by attraction between molecules surface of liquid

water is less dense as a solid than as a liquid

water expands when it freezes

forms relativiy open crystal structions

WHY ICE FLOATS

water absorbing heat

high capacity for absorbing energy

water has a very high specfic heat

many hydrogen bonds must be broken for water molecules to move faster

specfic heat

amount of energy needed to rise temp. of 1 gram of substance by 1C

water molecules

can dissociate into a hydrogen ion and a hydroxide ion

H2O into H + OH

chemical equilibrium

reactions are reversible

acids

pH less than 7

substances that give up protons during chemical reaction and raise hydrogen ion concentrations

adding acid to solution increases proton concentration of solution

bases

pH greater than 7

substances that acquire protons during chemical reactions and lower hydrogen ion concentrations

adding basess to a solution decreases proton concentration

pH(power of hydrogen)

logarthic notation used to express concentrations of protons in a solution

pH scale

one unit of pH representd change in concentration of hydrogen ions equal to factor of 10

nuetral pH

7pH

indicates neither acidic or basic

buffers

helps maintain homostatis

carbon

almost all molecules in organism have this atom

except for water

forms 4 covalent bonds due to its 4 valence electons

organic compunds

molecules that contain carbon bonded to other molecules

limitless arrays of molecular shapes

different combinations of single and double bonds

marcromolecules

large molecules made of smaller molecules subunits called (monomers)

large number of monomer bonded togather via polymerization

condensation reaction (dehydration reaction)

monomer polymerize via condensation reactions

newly formed bonds relsuts in less water molecules

hydrolysis

The opposite of a condensation reaction

Water molecules react with bonds linking monomers, separating them from the polymer chain