1.1: Chemistry in Living System

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

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

functional group

class of compounds

structural formula

hydroxyl

alcohols

R-OH

aldehyde

aldehydes

R-CHO

keto

ketones

R>CO

carboxyl

carboxylic acids

R-COOH

amino

amines

R-NH2

phosphate

organic phosphates

R-OPO32-

sulfhydryl

thiols

R-SH

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

C6H14

molecular

C3H7

emperical

H3C-CH2-CH2-CH2-CH3

condensed

structural

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skeletal

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