What is chemistry?

What do you know about each of these?• Atom• Molecule• Element• Compound• Biochemistry

Biochemistry

Ch. 3 The Chemistry of Life

You’re a big bag of chemicals!

• Most of the human body is made up of water, H2O, with cells consisting of 65-90% water by weight.

• Most of a human body's mass is oxygen. Carbon, the basic unit for organic molecules, comes in second.

• 99% of the mass of the human body is made up of just six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.

atom

• Basic unit of matter.

• Made up of protons, neutrons, and electrons

(100 million atoms = pinkie width)

http://www.csmate.colostate.edu/cltw/cohortpages/viney/atom.jpg

proton

• Small particle in nucleus (center) of atom.

• Positively charged.

• Number of protons = atomic number.

• Very small but important mass.

neutron

• same mass as protons.

• in nucleus with protons.

• no charge = Neutral

• held together with protons by strong forces.

electron

• Negatively charged particle.

• Attracted to positively charged nucleus.

• Constantly in motion in electron cloud outside nucleus.

• Very small mass (1/1840 mass of proton).

• # of electrons = # of protons, so atoms are neutral in charge.

element

• Pure substance made of atoms with same # of protons.

• > 100 known.

• Represented by one or two letter symbols: C, O, Ca, Fe

• Organized in Periodic Table of Elements.

http://www.corrosionsource.com/handbook/periodic/periodic_table.gif see also your testbook p.1064

compound

• 2 or more different elements chemically bonded

• Shown by chemical formula: H2O

molecule

• A group of atoms held together by covalent bonds.

ex: C6H12O6

• Not all molecules are compounds.

Ex: O2

Chemical bonds

valence electrons = Electrons in the outermost level of electron cloud.

http://members.tripod.com/craigjm/Atom2-2.jpg

chemical bonds

2 types: Ionic and Covalent

• Ionic bonds - electrons are moved from one atom to another to form ions (charged atoms).

• Oppositely charged ions are attracted to each other. Ex: Na+ and Cl- are ions.

• Covalent bonds - electrons are shared between atoms.

• Molecule - atoms joined by covalent bonds. Can be the same or different elements Ex: H2O , O2

• Molecules with partial charges on opposite ends are polar molecules. Ex: H2O

More protons in oxygen nucleus attract shared electrons to O end of molecule.

• Oxygen end of molecule = slightly negative.• Hydrogen end = slightly positive.

polarity

Water is a polar molecule!

• Other molecules, like CO2, are nonpolar.

Their electrons are distributed evenly, so they have no charge.

• Polar molecules do not “like” nonpolar molecules; they will not mix because they have no attractive charges.

Carbon dioxide CO2 (nonpolar molecule)

Hydrogen BondsAttraction between partial positive charge of hydrogen end (-)

and partial negative charge of oxygen end (+).

http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/graphics/water.gif

Cohesion: the attraction between molecules of the same substance.

http://wwwchem.csustan.edu/chem2000/Exp5/bulk_h2o.gif

Adhesion - attraction between molecules of different substances.

http://www.dnareplication.info/images/dnadoublehelix2.jpg

DNA

Hydrogen bonds holdDNA molecules together

Water

• Exists as solid, liquid, and gas on surface of Earth.

http://food.oregonstate.edu/images/learni/w20.jpg

Ice Floats

• When water freezes, hydrogen bonds lock the molecules in place with spaces between them.

• Ice is less dense than water, so rivers and lakes don’t freeze solid.

Why is this important to living things?

Water absorbs and retains heat

• H-bonds always breaking and forming so…

• Water absorbs lots of heat and takes a long time to cool.

• Large bodies of water moderate the temp. of earth

Mixture - material composed of two or more elements or compounds that are PHYSICALLY MIXED, NOT chemically combined.

Ex: salt and pepper, gases in atmosphere.

solutions

• Mixtures of liquids.

• When something dissolves in water, the water molecules surround the ions of the substance.

• The water is the solvent.• The dissolved substance is the solute.

Water molecules can react to form ions.

H2O + H2O H3O+ + OH-

(water hydronium ion + hydroxide ion)

(In pure water, only 1 out of 550 million molecules forms ions.)

acids

acid = compound that forms extra hydronium ions when dissolved in water.

Acidic solution have higher concentration of H3O+ ions than pure water and pH below 7.Ex: vinegar, lemon juice

bases

base = compound that gives hydroxide ions in solution.

Basic solutions have lower concentrations of H3O+ than pure water and have pH higher than 7.

Ex: bleach, lye, ammonia

pH scale• “Potential of hydrogen”• Measure of how acidic or basic a solution is

• Shows concentration of H3O+

• Ranges from 0 - 14• Lower numbers = more acidic• Higher numbers = more basic

• Each point is 10x the H3O+ ion concentration of the previous level.

http://www.guardiantrader.com/images/ph_scale.gif

Buffers

• Substance that reacts to prevent sharp, sudden changes in pH.

Ex: baking soda

• Oxygen (65%) • Carbon (18%) • Hydrogen (10%) • Nitrogen (3%) • Calcium (1.5%) • Phosphorus (1.0%) • Potassium (0.35%) • Sulfur (0.25%) • Sodium (0.15%) • Magnesium (0.05%) • Copper, Zinc, Selenium, Molybdenum, Fluorine, Chlorine,

Iodine, Manganese, Cobalt, Iron (0.70%) • Lithium, Strontium, Aluminum, Silicon, Lead, Vanadium,

Arsenic, Bromine (trace amounts) • Reference: H. A. Harper, V. W. Rodwell, P. A. Mayes, Review of

Physiological Chemistry, 16th ed., Lange Medical Publications, Los Altos, California 1977.