what is chemistry? what do you know about each of these? atom molecule element compound biochemistry

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.