Unit 3 – Lecture 2

Levels of Organization – review Atom Molecule Biomolecule [aka macro- molecule] Organelle Cell Tissue Organ Organ system Organism

Molecules Molecule – composed of two or more atoms can be made of a single element or multiple elements has no overall charge example: H 2 – two atoms of hydrogen

Molecules – cont’d Compound – a molecule made of two or more elements my abbreviation = cmpd(s) MUST have more than one element present Ex: H 2 O [2 atoms of hydrogen, 1 atom of oxygen] ionic compounds have a positive or negative charge Ex: NH 4+

Molecules – cont’d Types of Bonds Covalent Bonds formed when atoms share valence electrons “co” – together valence electron – electron in the outermost shell of an atom a strong bond Ex: H 2 O

Molecules – cont’d Types of Bonds Ionic Bonds formed when atoms gain or lose electrons by transfer weaker than a covalent bond Ex: NaCl

Properties of Water Approximately 2/3 of your body is water…so apparently it’s quite important… What makes water so important??

Water is a Polar Molecule Polar 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 itself uneven distribution of electrons leads to a negative pull on one side

Water is a Polar Molecule The oxygen side of the molecule is much more electronegative than the hydrogen side

Water is a Polar Molecule It is the “Universal Solvent” water given this term because it is able to dissolve many substances this 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 Molecule Polar is aka Hydrophilic hydrophilic: literally, “water-loving” “hydro” = water “philos / phil / philia” = to love dissolve easily in water [like sugar] hydrophobic: literally, “water- fearing” “phobia / phobic / phobos” = to fear aka non-polar do not dissolve or mix easily in water [like lipids]

Water Performs H-Bonding Hydrogen Bond: bond formed between a H and a more electronegative atom is very weak is not a true “bond” but an attraction usually takes place between oxygen [O], nitrogen [N], or fluorine [F]

Water Performs H-Bonding Adhesion – 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 level aka capillary action major way blood flows through the capillaries in your body and through the roots of plants.

Water Performs H-Bonding Cohesion – the ability of water to form H-bonds with other water molecules causes surface tension Ex: water drops form small spheres, can overfill a glass, some bugs can walk on water

Water Expands when Freezing is less dense when frozen; most substances are more dense allows it to float on water when frozen if ice sunk, lakes & ponds would freeze solid in winter

Water has a High Specific Heat Specific Heat – amount of energy it takes for the temperature of a substance to increase or decrease makes homeostasis MUCH easier

Mixtures Mixture – a combination of multiple substances that… can be physically separated are not combined chemically can be homogenous or heterogenous

Mixtures – cont’d Mixtures can be homogenous or heterogeneous homogenous – appearance and consistency are the same throughout “genous” – type typically called solutions heterogeneous – appearance & consistency are different throughout Ex: …?

Mixtures – cont’d Solution – a mixture that… is homogenous is in a single phase solid, liquid, or gas can have different phases dissolved in one another gas in liquid [carbonated water] solid in solid [alloys – carbon/iron = steel; copper/zinc = brass] solid in liquid [sugar water] etc.

Mixtures – cont’d uses the term “solute” & “solvent” solubility – the ability of a substance to dissolve in another