AP Bio Unit 1.1

elements

six main of these in living organisms = CHNOPS

97% human body

trace _______ (K, Fe, Na, Ca, Cl, etc) make up others

half-life

amount of time it takes for half of radioactive isotopes to decay and become more stable

used in radioactive dating

tracers

radioisotopes used to “label” and track biological molecules (ex. with viruses)

valence shell

8 valence electrons, when bonding happens

ionic bonds

transfer electrons, become negatively or positively charged

form salts (dissolves in water from broken bonds)

covalent bonds

sharing of electrons

form molecules

don’t dissolve in water (bonds NOT broken) but can separate from each other to dissolve

requires chemical reactions to break

nonpolar

share electrons equally, no partial positive or negative charge

hydrophobic

polar

do not share electrons equally, partial positive and partial negative region

hydrophilic

molecular shapes

3d, results from covalent bonding

key to function

similar have similar functions

hydrogen bonding

because water is very polar, hydrogen takes on strong partial positive and FON takes on strong partial negative

single easily broken but many are collectively strong

cohesion and adhesion

because of h bonds, cling to each other or other polar surfaces

create capillary action (“climb” narrow spaces) —> water transported up plants against gravity (transpiration)

surface tension

force created from surface molecules attracted to below molecules

water has high of this because cohesion

form droplets (max h bonds), resistant to breaking

specific heat capacity

high in water because it absorbs lots of thermal energy without a big temp change

organisms have lots of water to maintain internal temperatures, coastal habitats have more stable climates

heat of vaporization

water has high of this because liquid has to absorb a lot of heat to break h bonds

like sweat! water takes away heat when evaporated

expands

water does this when it freezes because H BONDS STABILIZE and move apart from each other

less dense as ice

insulates lake animals and keeps it from fully freezing (ice floats)

universal solvent

water is this because of polarity

blood and cells can dissolve and transport many substances

acids

more [H+], pH less than 7

bases

more [OH-], pH greater than 7

organic molecules

carbon based molecules that exist because of living things

carbon

has 4 valence electrons, forms 4 stable covalent bonds —> huge diversity of big molecules

hydrocarbon chains, branches, and rings

functional groups

replace hydrogen in carbon backbone

determine chemical reactivity and polarity

ethanol H to OH —> hydrophobic to hydrophilic

estrogen and testosterone almost the same, but have two different functional groups so have very different effects

macromolecules

organic in living things; repeating units of monomers form a polymer

dehydration reaction

monomers connect to make polymers with a covalent bond that produces a water molecule

hydrolysis reaction

breaks polymers to monomers by CLEAVING covalent bond using a necessary water molecules

enzymes

catalyst, not consumed or changed by reaction it speeds up