Topic 1:Chemicals of life 1.Molecules and Atoms 2.Water 3.Carbon and other elements

1. Atoms and Molecules 1.1 Elements and Compounds 1.2 Elements of Life 1.3 Chemical and Physical Bonds 1.4 Importance of Carbon, Nitrogen, and Water

Organisms are composed of matter. Matter is made up of elements. Elements combine to form compounds. anything that has mass and takes up space cannot be broken down to other substances by chemical reactions

SodiumChloride Sodium Chloride + compounds have characteristics different from those of their elements Emergent Properties

Essential Elements (elements required by living organisms) macroelements C, H, O, N 96% of living matter microelements Na, K, Ca, Mg, P, S, Cl 4% of living matter trace elements Fe, I, Cu, Mn, etc. required in minute (tiny) amounts

the properties of elements depend on the chemical characteristics of their atoms

chemical characteristics of atoms depend on the arrangement of electrons in electron shells (electron configuration)

Electronegativity the attraction of an atom for electrons from other atoms important property of elements of life

Bonds Chemical Bonds Physical Bonds form between elements form between molecules Covalent Ionic Dipole Interactions Van der Waals

Chemical Bonds Covalent Bonds Ionic Bonds elements of similar electronegativity share pairs of electrons elements of very different electronegativity transfer electrons, creating ions (anions and cations)

The properties of a compound (solubility, melting point, etc.) depend on the type of bonding involved.

Covalent bonds are the most important in biological molecules because they allow for a variety of properties they can be single, double, or triple bonds HH single covalent bond OO double covalent bond NN triple covalent bond

Covalent bonds can be classified as non-polar or polar create dipoles - molecules with partial negative (-) and positive (+) charges at opposite ends non-polar covalent bonds (elements of the same or almost the same electronegativity) ethane polar covalent bonds (elements of slightly different electronegativity) water

weak attractions between molecules (not the result of chemical reactions) Physical Bonds

There are two major types of Physical Bonds Dipole Interactions Attraction between opposite poles of polar molecules (dipoles) Van der Waals Interactions (aka London Dispersion Forces) Caused by momentary asymmetric distribution of moving electrons in large non-polar molecules.

 – –  + +  + + Water (H 2 O) Ammonia (NH 3 ) O H H  + +  – – N H H H ++ ++ Hydrogen Bonds the most important dipole interaction in biology forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom from a different molecule

bonds determine the shape of the molecule

Shape of a Molecule determines the biological function Differently-shaped molecules have different functions similar shape molecules can mimic the function of another molecule (morphine/endorphins)

Carbon is the element most widely used in biomolecules due to its special properties. Organisms can obtain carbon in two ways: inorganic carbon (CO 2 ) autotrophs organic carbon (glucose) heterotrophs

Nitrogen is also essential to living organisms, making part of proteins and nucleic acids. Organisms can obtain nitrogen in two ways: inorganic nitrogen (N 2 ) atmosphere – microorganisms, fungi minerals – nitrates for plants organic nitrogen from other organisms

Water fundamental to life organisms are composed mostly of water (65% in humans, 99% in jellyfish) most chemical reactions in organisms take place in water (wet chemistry)