CHEMISTRY THE STUDY OF INTERACTIONS OF ATOMS & MOLECULES

DEFINITIONS MATTER -Has weight & occupies space -Composed of elements ELEMENT -Simplest chemical substance with unique chemical properties -92 natural -26 in humans

ELEMENT continued -96% (body weight) *Hydrogen *Oxygen *Carbon *Nitrogen -Each element composed of similar atoms

ATOMS Smallest unit of element, retaining the chemical characteristics of that element Smallest unit in chemical reactions Smallest structural unit in our bodies Subatomic particles: -Proton *Positive charge *Weighs one atomic unit

ATOMS continued -Neutron *No charge *One atomic unit -Electron *Negative charge *No significant weight

ATOMS continued Atomic number -Number of protons in atom Atomic weight -Sum of proton & neutrons Atomic symbol -Each element represented by letter(s)

ATOMIC ARRANGEMENT Central nucleus of protons & neutrons Electrons in orbitals (shells) Inner orbital “full” with 2 electrons Second orbital holds up to 8 Third orbital holds 18 Valence = outermost orbital with any electrons

Atoms & Electron Shells

ATOMIC ARRANGEMENT continued The number of valence electrons affects atomic reactivity -Stable if valence is full -Reactive/unstable if incomplete valence Atoms can: -Gain/lose electrons -Lose excess neutrons (Radioactive Isotopes) -Protons are NEVER lost or gained

MORE DEFINITIONS Molecule -Two or more atoms bonded together (O 2 ) Compound -Two or more elements in a fixed ratio (H 2 O) Chemical Formula -Indicates number of atoms of each element in a molecule (CO 2 )

CHEMICAL BONDS Join atoms by valence electrons Electrons gained, lost or shared to fill valence 3 Types: -Ionic or Electrovalent -Covalent -Hydrogen

CHEMICAL BONDS continued IONIC BONDS -Transfer of electrons between atoms -Atoms that GAIN electrons have a net negative charge (anion) -Atoms that LOSE electrons have a net positive charge (cation) -Oppositely charged ions are mutually attractive -Common in inorganic molecules

CHEMICAL BONDS continued COVALENT BONDS -Electrons shared between atoms -Common in organic molecules Chemical bonds represent STORED ENERGY -Bond formation requires energy -Energy is released when bonds are broken

Polar & Nonpolar Covalent Bonding

CHEMICAL BONDS continued HYDROGEN BONDS -Form weak attraction within or between polar molecules -Involves association between slightly positive H and two other atoms (slightly negative O or N) -Easily broken by Temp or pH -Found in: H 2 O, Proteins, Nucleic Acids

Hydrogen Bonding

CHEMICAL REACTIONS SYNTHESIS -A + B  AB -Form bond, requires energy -Dehydration Synthesis *Water released as bond formed *E.g. Glycogen from glucose

Dehydration Synthesis

CHEMICAL REACTIONS continued DECOMPOSITION -AB  A + B -Breaks bonds, releases energy -Hydrolysis *Reverse of dehydration synthesis *Water used to help break bonds *E.g. Digestion of proteins into amino acids

Hydrolysis

CHEMICAL REACTIONS continued EXCHANGE -AB + C  AC + B -Involves synthesis & decomposition -Bonds broken & formed -E.g. Glucose + ATP  Glucose phosphate + ADP

INORGANIC COMPOUNDS Involve ionic bonds Don’t contain carbon (CO & CO 2 exceptions) Inorganic compounds common in cells: -Water -Oxygen (use to release energy from food) -Carbon dioxide (metabolic waste product) -Inorganic salts

INORGANIC COMPOUNDS continued Water -Most common inorganic -2/3 of body by weight -95% of cell -Solvent (dissolved substances) -Lubricant -High heat capacity

INORGANIC COMPOUNDS continued Salts -Ionic compounds -Dissociate in water -Source of ions  electrolytes -Maintain water balance -Involved in blood clotting, muscle & nerve physiology

INORGANIC COMPOUNDS continued Acids & Bases -Acid *Releases hydrogen ions (H + ) in solution *pH < 7.0 *Strong acids completely dissociate in water -Base *Releases hydroxide ions (OH - ) in solution *pH > 7.0

pH Scale -Measures [H + ] in solution -Log scale (ten- fold increase between numbers) -0 to 14, 7.0 is Neutral

Buffers -Resist changes in pH -Pick-up or release H +, keep pH of solution relatively stable -E.g. carbonic acid (H 2 CO 3 ) from CO 2 + H 2 O

ORGANIC COMPOUNDS Involve covalent bonds Contain carbon Include: -Carbohydrates -Lipids -Proteins -Nucleic acids

ORGANIC COMPOUNDS continued Carbohydrates -(CH 2 0) n -Built of monosaccharide(s) -Quickest source of energy (4 cal.gram) -May be stored for energy reserves

Glucose

CARBOHYDRATES continued Monosaccharides -Simple sugars -Ribose (5-carbon ring), Glucose (6-carbon ring), Fructose, Galactose Disaccharides -2 monosaccharides joined by dehydration synthesis (Glucose X 2 = Maltose) Polysaccharides -Long chain monosaccharides (complex carbs) -Glycogen is a polymer of glucose

Glycogen

ORGANIC COMPOUNDS continued Lipids -Composed of Fatty Acids + Glycerol (3:1) -Source of maximum energy; long-term energy storage -Insoluble in water -Make-up most of cell membrane

ORGANIC COMPOUNDS continued Proteins -Composed of Amino acids joined by peptide bonds -23 amino acids vary only in R-group -Chain of amino acids = Polypeptide -Most abundant organic compound -Functions: Structural, Carriers, enzymes, hormones, Antibodies, Buffers

Amino Acid Structure

PROTEINS continued Complex, 3-D shape determines function -Primary Level = order of amino acids in polypeptide -Secondary Level = twisting & folding of chain, held by hydrogen bonds -Tertiary Level = 3 Dimensional shape, determine function -Quaternary Level = multiple polypeptide chains

Hemoglobin

ENZYMES Protein Catalyst - Increase rate of reaction Remain unchanged Reaction specific; substrates bind at active site Function best at optimal pH & temperature

ORGANIC COMPOUNDS continued Nucleic Acids -Composed of Nucleotides *Phosphate group *Sugar (Ribose or Deoxyribose) *Nitrogenous Base  Adenine & Guanine  Thymine, Uracil (RNA), & Cytosine

NUCLEIC ACIDS continued Complementary base pairing Phosphate group & sugar form backbone Bases joined by hydrogen bonds & form rungs DNA = Deoxyribonucleic Acid -Deoxyribose -Thymine (NOT uracil) -Double-stranded -Codes for Proteins

NUCLEIC ACIDS continued RNA = Ribonucleic Acid -Ribose -Uracil (NOT thymine) -Single-stranded -Involved in Protein Synthesis

Nucleic Acids: RNA and DNA

The Structure of ATP