The Chemistry of Life

The Basics

• What are the properties of matter? – Mass and volume

• What are the phases of matter? – Solid, liquid, gas

• What is the smallest unit of matter?

• How are atoms and elements related?

• What is a compound, molecule, ion?

The Atom

Atoms

• An element is a substance that is made entirely from one type of atom

• All isotopes of a particular element have the same number of protons, but have a different number of neutrons.

• All known elements are arranged on a chart called the Periodic Table of Elements.

The Periodic Table

Compounds

• A compound is a substance formed when two or more elements are chemically joined. Water, salt, and sugar are examples of compounds.

Covalent Bonding

• Sharing pair of valence electrons

• Number of electrons required to complete an atom’s valence shell determines how many bonds will form

• Ex: Hydrogen & oxygen bonding in water; methane

Ionic bonding

• High electronegativity difference strips valence electrons away from another atom

• Electron transfer creates ions (charged atoms)

• Cation (positive ion); anion (negative ion)

• Ex: Salts (sodium chloride)

Hydrogen bonds

• Hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom (oxygen or nitrogen)

van der Waals interactions

• Weak interactions between molecules or parts of molecules that are brought about by localized change fluctuations

• Due to the fact that electrons are constantly in motion and at any given instant, ever-changing “hot spots” of negative or positive charge may develop

Chemical Reactions

• A chemical reaction is the pathway by which two substances bond together. 

• In fact we have already discussed several chemical reactions.  One we have mentioned is the reaction of hydrogen with oxygen to form water.  To write the chemical reaction you would place the reactants (the substances reacting) on the left with an arrow pointing to the products (the substances being formed). 

Chemical Reactions

H2 + O2 → H2O

To write a chemical reaction correctly, the number of atoms on the left side of a chemical equation has to be precisely balanced with the atoms on the right side of the equation. 

2H2 + O2 → 2H2O

Chemical Reactions

CH4 + O2 → CO2 + H2O becomes

CH4 + O2 → CO2 + 2H2O and then

CH4 + 2O2 → CO2 + 2H2O

Exothermic Reactions

Endothermic Reactions

Water

• Polar~ opposite ends, opposite charges• Cohesion~ H+ bonds holding molecules

together• Adhesion~ H+ bonds holding molecules to

another substance• Surface tension~ measurement of the

difficulty to break or stretch the surface of a liquid

• ……….

Acid/Base & pH

• Dissociation of water into a hydrogen ion and a hydroxide ion

• Acid: increases the hydrogen concentration of a solution

• Base: reduces the hydrogen ion concentration of a solution

• pH: “power of hydrogen”• Buffers: substances that

minimize H+ and OH- concentrations (accepts or donates H+ ions)

Mixtures

• Homogeneous mixture: Substance in which components are evenly mixed, (example: toothpaste, milk, perfume, steel, etc)

• Heterogeneous mixture: Substance in which components are not evenly mixed. (Don't blend together)

Solutions and Suspensions

• A solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent. A common example is a solid, such as salt or sugar, dissolved in water, a liquid.

• A suspension is a heterogenous fluid containing solid particles that are sufficiently large for sedimentation.

• A colloid is a type of mechanical mixture where one substance is dispersed evenly throughout another. Example: milk

Enzymes

• Enzymes are catalysts which speed up the rate of the reaction but do not become part of the product(s)– Most enzymes are proteins

• Enzymes bind temporarily to one or more of the reactants of the reaction they catalyze. In doing so, they lower the amount of activation energy needed and thus speed up the reaction.

Enzymes

• A substrate (reactant) molecule binds to its enzyme like a key in a lock.

Factors Affecting Enzyme Activity

• Enzyme Concentration

• Substrate Concentration

• Temperature

• pH

• Inhibitors