Chemical Basis of Life

Chemistry

• Matter is made up of separate chemical components.– Chemistry = Interactions between atoms/molecules.

• Biological function begins at the chemical level.– Hierarchical interactions add function.– Ex. Photosynthesis

Sub-cellular concepts

• Matter

• Elements

• Atoms

• Natural elements– 92– About 25 essential for life– H,O,N,C = 96% of human body– Trace elements

Periodic Table of Elements

Atomic Structure• 3 Basic subatomic particles.

– Proton– Electron– Neutrons

• Atomic Number

• Atomic Mass

• Compounds

Isotopes• Atoms representing different forms of the

same element.

• Same number of Protons, but different mass– Different number of neutrons

• Radioactive Isotopes

Electrons

• Arranged in shells

• Valence

• Reactivity

• Molecules

Molecular Structure• Structural formula

• Ball and stick

Chemical Bonding – Ionic Bonds

• Form between Ions of opposite charge

• NaCl– One atom gives up e- (cation).– One atom recieves e- (anion).– Results in filled outer shells for both.

Chemical Bonding – Ionic Bonds

Chemical Bonding – Covalent Bonds• Result from electron sharing.

– 1 or more pairs of outer shell electrons.– Number of possible bonds = number

needed to fill outer shell.

Chemical Bonding – Hydrogen Bonds

• Attraction between the (+) and (-) ends of a water molecule

• Weak bonds

• Hydrogen = positive end

• Oxygen = negative end

Water

• Polar molecule– Electronegativity– Polar covalent bonds

• Cohesion

• Adhesion

• Resistant to temperature change

More Definitions

• Solutions– Solvent– Solute

• Aqueous solution = Water is the solvent– Water = Universal solvent– Results from the Polarity

pH

• Potential hydrogen.

• H2O dissociates into H+ and OH- (hydroxide) ions.– Acids– Bases

• pH scale

pH Scale

Chemical Reactions

• Processes producing chemical changes in matter.– Reactants– Products

• Matter cannot be created or destroyed

• Energy flow

Types of Chemical Reactions

• Synthesis – Ex. A + B => AB

• Decomposition– Ex. AB => A + B

• Exchange– Ex. AB + CD => AC + BD

• Oxidation-Reduction (redox)– Ex. C6H12O6 + 6O2 6CO2 + 6 H2O + ATP