Unit 3 – Lecture 2

Levels of Organization – reviewAtomMoleculeBiomolecule

[aka macro-molecule]

Organelle

CellTissueOrganOrgan systemOrganism

MoleculesMolecule – composed of two or more atoms

can be made of a single element or multiple elements

has no overall chargeexample: H2 – two atoms of hydrogen

Molecules – cont’dCompound – a molecule made of two or more

elementsmy abbreviation = cmpd(s)MUST have more than one element presentEx: H2O [2 atoms of hydrogen, 1 atom of

oxygen]ionic compounds have a positive or

negative chargeEx: NH4+

Molecules – cont’dTypes of BondsCovalent Bonds

formed when atoms share valence electrons“co” – together valence electron – electron in the outermost

shell of an atoma strong bondEx: H2O

Molecules – cont’dTypes of BondsIonic Bonds

formed when atoms gain or lose electrons by transfer

weaker than a covalent bondEx: NaCl

Properties of WaterApproximately 2/3 of your body is water…so

apparently it’s quite important…

What makes water so important??

Water is a Polar MoleculePolar Molecule: has no overall charge [hence…

“molecule”] but has a side that is more electronegative

electronegativity – the ability of an atom to attract electrons to itselfuneven distribution of electrons leads to a

negative pull on one side

Water is a Polar MoleculeThe oxygen side of the molecule is much

more electronegative than the hydrogen side

Water is a Polar MoleculeIt is the “Universal Solvent”

water given this term because it is able to dissolve many substancesthis is because of its polarity

solvent: a substance that is used to dissolve a solute.

solute: a substance that is dissolved by the solvent

Ex: water [solvent] dissolves sugar [solute]

Water is a Polar MoleculePolar is aka Hydrophilic

hydrophilic: literally, “water-loving”“hydro” = water“philos / phil / philia” = to lovedissolve easily in water [like sugar]

hydrophobic: literally, “water- fearing”“phobia / phobic / phobos” = to fearaka non-polar do not dissolve or mix easily in water [like

lipids]

Water Performs H-BondingHydrogen Bond: bond formed between a H

and a more electronegative atomis very weakis not a true “bond” but an attractionusually takes place between oxygen [O], nitrogen [N], or fluorine [F]

Water Performs H-BondingAdhesion – the ability of water to form H-bonds

with other molecules [to “stick” to other things ]

think “adhesive”ex: straw in water

water climbs above the surface levelaka capillary action

major way blood flows through the capillaries in your body and through the roots of plants.

Water Performs H-BondingCohesion – the ability of water to form H-bonds

with other water moleculescauses surface tensionEx: water drops form small spheres, can

overfill a glass, some bugs can walk on water

Water Expands when Freezingis less dense when frozen; most substances are more denseallows it to float on water when frozenif ice sunk, lakes & ponds would freeze solid

in winter

Water has a High Specific HeatSpecific Heat – amount of energy it takes for

the temperature of a substance to increase or decrease

makes homeostasis MUCH easier

MixturesMixture – a combination of multiple substances

that…can be physically separatedare not combined chemicallycan be homogenous or heterogenous

Mixtures – cont’dMixtures can be homogenous or heterogeneoushomogenous – appearance and consistency

are the same throughout “genous” – typetypically called solutions

heterogeneous – appearance & consistency are different throughoutEx: …?

Mixtures – cont’dSolution – a mixture that…is homogenousis in a single phase

solid, liquid, or gascan have different phases dissolved in one

anothergas in liquid [carbonated water]solid in solid [alloys – carbon/iron = steel;

copper/zinc = brass]solid in liquid [sugar water]etc.

Mixtures – cont’duses the term “solute” & “solvent”solubility – the ability of a substance to

dissolve in another