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 reactionsSmallest structural unit in our bodiesSubatomic 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 & neutronsElectrons in orbitals (shells)Inner orbital “full” with 2 electronsSecond orbital holds up to 8Third orbital holds 18Valence = 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 (O2)

Compound- Two or more elements in a fixed ratio (H2O)

Chemical Formula- Indicates number of atoms of each element

in a molecule (CO2)

CHEMICAL BONDS

Join atoms by valence electronsElectrons gained, lost or shared to fill

valence3 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: H2O, 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 bondsDon’t contain carbon (CO & CO2

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 (H2CO3) from CO2 + H2O

ORGANIC COMPOUNDS

Involve covalent bondsContain carbonInclude:

- Carbohydrates- Lipids- Proteins- Nucleic acids

ORGANIC COMPOUNDS continued

Carbohydrates- (CH20)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, GalactoseDisaccharides

- 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

ProteinCatalyst - Increase rate of reactionRemain unchangedReaction specific; substrates bind at

active siteFunction best at optimal pH &

temperature

Fig. 2.18

ORGANIC COMPOUNDS continued

Nucleic Acids- Composed of Nucleotides

* Phosphate group* Sugar (Ribose or Deoxyribose)* Nitrogenous Base

Adenine & GuanineThymine, Uracil (RNA), & Cytosine

NUCLEIC ACIDS continued

Complementary base pairing Phosphate group & sugar form backboneBases joined by hydrogen bonds & form rungsDNA = 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