Chapter 2: The Chemistry of Life Mr. Grivensky/Mr. Rutkoski

Elements and Atoms A chemical element is a substance that cannot be broken down into another substance The smallest unit of an element is an atom 1,000,000 atoms placed side by side would only measure about 1 cm across

Parts of an Atom There are 3 main parts of an atom ParticleLocationCharge ProtonNucleusPositive (+) ElectronOrbits the NucleusNegative (-) NeutronNucleusNeutral, No charge

Atoms Most of the mass (99.9%) of an atom is found in the nucleus The mass of an electron is about 1/2000 that of a Proton The opposite charges of the electrons and protons keep the electrons orbiting the nucleus Atoms of different elements differ in the number of protons, electrons, and neutrons

Bonds and Compounds There are 92 natural elements About 20 more have been created in laboratory settings Atoms form chemical bonds with other atoms to form compounds They bond in such as way as to create stable arrangements

Ionic Bonds An ion is an atom that has gained or lost an electron If an atom loses an electron, it has a positive (+) charge Atoms that gain an electron have negative (-) charges Two oppositely charged ions are attracted to one another and may form a compound

Ionic Bond Example Sodium chloride (NaCl) Na loses an electron and becomes Na + Cl gains an electron and becomes Cl - These two are attracted to one another and form NaCl

Covalent Bonds Covalent bonds form when 2 or more atoms share electrons These compounds are called molecules Molecules may contain few atoms (H 2 O) or even millions (DNA) The more electrons the atoms share, the stronger the bonds between the atoms

Chemical Formulas A chemical formula indicates the elements present in a compound and the proportions in which they combine Examples: H 2 0 (water) 2 Hydrogen atoms and 1 Oxygen C 6 H 12 O 6 (glucose) 6 Carbon, 12 Hydrogen, and 6 Oxygen

Water Liquid water is found inside every cell and most cells are surrounded by water Water is a polar molecule In a polar molecule the electrons are shared, but they spend more time around one atom than another Since the electrons in water spend more time around the Oxygen atom, that end of the molecule is slightly positive, while the Hydrogen side is slightly negative

Solutions When water dissolves a substance it forms a solution The compounds found in cells are often found in solutions containing water and dissolved chemicals This is one of the reasons water is so important to living things Parts of a solution Solute: The part that is in the smaller amount Solvent: The part that is in the larger amount Example: Salt water Water = greater amount = solvent Salt = smaller amount = solute

H+ and OH- ions Water has the ability to break down into ions of its own This results in the formation of H+ (Hydrogen ions) and OH- (Hydroxide ions) The H+ and OH- ions are two of the most reactive ions found in nature H 2 OH + + OH -

Acids and Bases Certain compounds dissociate in water to form ions Acids are compounds that produce H + ions Example: Hydrochloric acid is formed in the stomach when it dissociates HClH+H+ +Cl -

Bases Bases are compounds that produce OH - ions Example: Sodium hydroxide (NaOH) NaOHNa + +OH -

pH Scale The pH scale is used to indicate the strength of an acid or base Acids have a pH of 0 to 6 Bases have a pH of 8 to 14 A pH of 7 is considered neutral

pH Scale pH is actually a measurement of the H + ions produced A substance that produces H+ ions =.0001 ions has a pH of 3 (acid) A substance that produces H+ ions = ions has a pH of 9 (base)

Carbon Carbon is an especially important element to all living things Organic compounds are compounds which contain at least 2 Carbon atoms Carbon typically forms 4 covalent bonds to become stable It has the ability to combine with many different elements It also has the ability to form chains of Carbon atoms

Macromolecules Macromolecules are very large polymers Polymers are large molecules which are made up of many small molecules called monomers There are 4 main groups of macromolecules which are important to living things; carbohydrates, lipids, proteins, and nucleic acids

Carbohydrates Sugars and starches are examples Carbohydrates are made up of Carbon, Hydrogen, and Oxygen They usually contain 2x as many Hydrogen atoms as Oxygen atoms Example: Glucose: C 6 H 12 O 6

Carbohydrates Simple sugars make up most of the smallest of the carbohydrates Examples include: Galactose (Milk), Fructose (Fruits), and Glucose (in all cells) Each simple sugar has the same formula: C 6 H 12 O 6 ; they only differ in the arrangement of the atoms Simple sugars are easy for the cells to produce and break down; they serve as the way for cells to store and release chemical energy

Carbohydrates Organisms can also use simple sugars to assemble larger polymers 2 simple sugars joined together form a disaccharide Table sugar (sucrose is an example) Simple sugars which contain only one sugar are called monosaccharides Polysaccharides contain many sugars which can be broken down when the cell needs a simple sugar or energy Plants store energy in the form of a polysaccharide known as starch Animals store energy in the form of a polysaccharide known as glycogen

Lipids Examples of lipids are waxes, fats, and oils Lipids are also a way to store energy but they have other functions as well

Proteins Proteins are polymers that are made up of monomers called amino acids There are 20 common amino acids which make up the majority of proteins Amino acids share a common structure

Amino acid Structure CC -- N OH H H HO R Carboxyl Group (COOH) Amino Group (NH 2 ) R Group Varies from one amino acid to another In Glycine the R group is a Hydrogen atom In alanine the R group is a Methyl group (CH 3 )

Amino Acids 2 or more amino acids can be joined together by the reaction of the amino group (NH2) of one amino acid and the carboxyl group (COOH) of another The bond formed is a chain and is called a peptide bond A chain of amino acids is known as a polypeptide

Proteins A complete protein is made up of many polypeptides and may contain other chemical groups Proteins are the major components of many structures including skin, muscles, and feathers