Elements of Life

• 92 naturally occurring elements

• carbon, hydrogen, nitrogen, oxygen, sulfur, phosphorus

  • carbon and hydrogen are backbone

  • other 4 give molecules specific properties

• atom=smallest particle that retains the properties of the element

  • protons, electrons, neutrons

  • #protons defines the element

  • electrons jump and allow atoms to bond

Isotopes

• of neutrons in an element can vary

• same element, differs in neutrons

• depends on atomic mass

  

Radioisotopes

• unstable isotopes, nucleus decays

  • ex. carbon 14→ nitrogen 14

• nuclear decay emitting radiation in the form of subatomic particles or electromagnetic waves

Molecules

• molecule = group of 2 or more atoms held together by chemical bonds

• covalent = shares electrons

• ionic = transfers electrons

  • disassociates in water

• organic = contains carbon and hydrogen, use covalent bonds

  • proteins, carbs, lipids, nucleic acids

• inorganic = ionic or covalent, no CH groups

  • water, oxygen gas, nitrogen gas, salt

Interactions Within Molecules

• intramolecular forces = hold atoms together within a molecule

• covalent bonds

• ex. water

Electronegativity

• some atoms attract electrons stronger than others

• ex. H2O

• 

• electronegativity increases from left to right on periodic table

Polar Covalent Bonds

• two atoms with different electronegativities share electrons

• electrons are imbalanced, more attracted to atom with higher electronegativity

• causes atom to have a slight negative charge

Interactions Between Molecules

• intermolecular forces = hold molecules together

• weak bonds

• broken easily, with sufficient energy

• responsible for physical properties of substances

Hydrogen Bonds

• weak association between an atom with a partial - charge and a hydrogen atom with a partial + charge

• ex. water

• 

• many hydrogen bonds together can be very strong

  • backbone of DNA

Hydrophobic Interactions

• non polar molecules (oils) do not form hydrogen bonds

• non polar + polar = non polars clump, don’t mix with polar

• hydrophobic = non polar molecules do not have attractive interactions with water molecules

• hydrophilic = polar molecules that have attractive interactions with water molecules

Ions in Biological Systems

• anion = negative ion (gains electrons, non metals)

• cation = positive ion (loses electrons, metals)

• cells are aqueous environments, ions become dissociated

• ex. Li+, Na+, K+

Hydrocarbons

• long chains of carbon backbone with hydrogen

• non-polar, do not dissolve, low boiling point, flammable, energy-rick

• ex. methane, propane, butane, octane, benzene

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Functional Groups

• functional groups = a cluster of atoms that always behaves in a certain wat

  • contains oxygen, nitrogen, phosphorus, or sulfur

• attached to carbon-based structure

Structure and Shapes of Molecules

• molecular formula = shows the # of each type of atom in an element or compound

  • ex. H2O, C3H7NO2, C6H12O6

• isomers=same formula, different structure

• structural formula=shows how atoms are bonded together