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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 (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 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: 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 bonds
Don’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 (tenfold 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 bonds
Contain carbon
Include:
-
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, 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
Fig. 2.18
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