Chapter 2

Atom Element = the smallest unit of matter that cannot be broken down = a pure substance made of only one kind of atom

Protons = positive electric charge (1+) Neutrons = neutral charge (0) Electrons = negative charge (1-) Atoms are composed of even smaller parts, called subatomic particles.

Each element has a unique number of protons = atomic number.

Atoms have equal numbers of P and e- –The atomic number = tells the number of protons and the number of electrons

Mass number = the sum of the number of protons and neutrons in the nucleus of an atom. # Neutrons = Mass # - Atomic # # protons? # electrons? # neutrons? Carbon =

Atoms of a given element may differ in the number of neutrons = isotopes. In nature, an element occurs as a mixture of isotopes. –For example, 99% of carbon atoms have 6 neutrons ( 12 C). –Most of the remaining 1% of carbon atoms have 7 neutrons ( 13 C) while the rarest isotope, with 8 neutrons is 14 C.

YouTube - The element song

6 C Carbon 12.01

Electron Shells Energy Levels  1 st Shell = 2 electrons 2 nd Shell = 8 electrons 3 rd Shell = 8 electrons (stable) PNPN e-

Atoms are mostly “empty space” If Nucleus = golf ball  e- 1km (10 football fields)

Electron Shells Energy Levels  Valence Electrons = electrons in outer energy shell Valence Electrons do the interaction during chemical reactions. The nuclei do not come close enough to interact.

Groups/Families Periods (+ Protons/electrons)  (Reactivity/Valence e-) 

???? ?? ? /8 Valence Electrons?

Atom Interaction? ~ 50 trillion cells Each cell 1,000’s atoms Valence Electrons

Atoms want to be “stable” = full valence shell. Share or transfer electrons. To become stable, atoms will hold together by chemical bonds. –The strongest chemical bonds are covalent bonds and ionic bonds. Chemical bonds

Chemical Bond Single Atoms

A covalent bond is the sharing of a pair of electrons by two atoms. Hydrogen HH H2H2  Subscript (2 atoms)

“Hydrogen Molecule” (H 2 ) Single Covalent Double Covalent Two or more atoms held together by covalent bonds constitute a molecule “Oxygen Molecule” (O 2 )

Ionic bond = one atom strips an electron completely from the other. NaCl Ions = charged atoms or molecule

YouTube - Carl Sagan on the chemical elementsYouTube - Carl Sagan on the chemical elements

Balloon Van de Graff Machine

Top 4 Atoms found in Organisms? O = 65% C = 18.5% H = 9.5% N = 3.3%

Astronomers Life evolved in water ~75% Earth Cells 70-95% Water

H2OH2O

Polar Covalent Bond = electrons not shared equally - + “Polar Molecule”

Hydrogen bonds = a weak chemical attraction between polar molecules. H+  O-

Up to 4 per water molecule

Cohesion = water molecules bonding to each other. “Surface tension” prevents stretch or break the surface

Adhesion = clinging of one substance to another (polar  polar).

Solution = homogenous mixture. Solute =Solvent = Water is the “solvent” of life dissolving agentsubstance dissolved

Forms hydrogen bonds with charged and polar covalent molecules. Solvent? Solute? “Dissolve”

pH Hydrogen Ion  H+ “Dissociation” H 2 O H + + OH - Acid = any compound that forms hydrogen ions (H+) ions in solution Base = any compound that forms hydroxide ions (OH-) in solution pH scale = concentration of H+ in a solution Buffers = weak acids or bases that prevent sudden changes in pH “Homeostasis”

pH

Hydrogen Ion  H+

Dissociation H 2 O H + + OH - In pure water only one water molecule in every 554 million is dissociated.

pH scale = concentration of H+ in a solution = neutral (H+ = OH-) 0-6 = acidic (H+) 8-14 = basic (OH-)

Base = any compound that forms hydroxide ions (OH-) in solution Acid = any compound that forms hydrogen ions (H+) ions in solution Factor of 10

Cell pH = 6.5 – 7.5 “Homeostasis” Buffers = weak acids or bases that prevent sudden changes in pH

CARBON COMPOUNDS “ORGANIC CHEMISTRY”

96% % Life depends on 25 elements “Trace elements”

Although cells are 70-95% water, the rest consists mostly of carbon-based compounds. Proteins, DNA, carbohydrates, and other molecules are all composed of carbon atoms bonded to each other and to atoms of other elements. “CARBON COMPOUNDS”

Organic chemistry = the study of carbon compounds (organic compounds). HONSPHONSP C bonds with:

3-D

Hydrocarbons “Petroleum”

Functional groupsunique properties

Macromolecules Form MONOMERS POLYMERS “Single” “Multiple”   Large Carbon Based Molecules  Bond

MACROMOLECULES ElementsMonomersExample Carbohy- drates C,H,O 1:2:1 Monosac- carhides Starch Glucose Sucrose Lipids C,H,OGlycerol Fatty Acids Fats Oils Cholesterol Proteins C,H,O,NAmino Acids Insulin Hemoglobin Nucleic Acids C,H,O, N, P NucleotidesDNA RNA

1. CARBOHYDRATES “Sugar” Main source of energy

Glucose C 6 H Monomer = “Monosaccharide” 1:2:1

“Polysaccharide” Starch Glucose Polymer =

Monomers: 2. LIPIDS (fats, oils, waxes) Glycerol Fatty Acid

Monomer Polymer

Straight Kinked Solid at room Temp (Bad) Liquid at Room Temp (Good) Double bond prevents “packing” Store energy

Steroids Cholesterol

3. PROTEINS AA—AA—AA—AA Monomer = Amino Acids “Peptide” Bond Polymer = “Polypeptide”

20 different Amino Acids “R Group”

Proteins: Control rate of reactions Regulate cell processes Form bone and muscle Transport substances into and out of the cell Fight disease

4. NUCLEIC ACIDS Monomers = Nucleotides

 Monomer  Polymer = Nucleic Acids (DNA/RNA)

YouTube - Carl Sagan on the chemistry of life on Earth/ other planetsYouTube - Carl Sagan on the chemistry of life on Earth/ other planets

CHEMICAL REACTIONS AND ENZYMES Energy = the ability to move or change mater Chemical reactions = chemical bonds between atoms are broken and new ones formed Chemical equations:Reactants  Products NaCl  Na+ + Cl- Metabolism = all the chemical reactions that occur in an organism Activation energy = the energy needed to start a chemical reaction Enzyme = a substance that increases the speed of chemical reactions Speeds-up reaction by reducing activation energy

Chemical reactions = chemical bonds between atoms are broken and new ones formed Reactants  Products NaCl  Na+ + Cl- Chemical equations: Energy is released or stored Na + Cl  Na + Cl -

Energy Releasing Reaction “Bonds Broken” NaCl  Na+ + Cl-

Energy Absorbing Reaction “Bonds Formed” Na + Cl  Na + Cl -

Metabolism = all the chemical reactions that occur in an organism

Activation energy = the energy needed to start a chemical reaction “Push” needed

Cells require activation energy Enzyme = a substance that increases the speed of chemical reactions “catalyst”

Speeds-up reaction by reducing activation energy

1. Substrate binds to enzyme 2. Substrate is converted to products 3. Products are released 4. Active site is available for another substrate active site substrate induced fit Enzymes are unaffected by the reaction and are reusable Reaction rate is substrate concentration dependant denature

End in “-ase” Amylase Catalase