1 11/9/2015 ATOMS. 2 11/9/2015 Major atoms in biology n C H O N S P n # of atoms in outer shell –...
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Transcript of 1 11/9/2015 ATOMS. 2 11/9/2015 Major atoms in biology n C H O N S P n # of atoms in outer shell –...
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ATOMS
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Major atoms in biology
Major atoms in biology
C H O N S P# of atoms in outer shell–H, 1–C 4–N, P 5–O, S 6
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C
N P
S
Atoms are sociable
HO
HChemical bonds
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Chemical bonds.....Chemical bonds.....
CovalentNoncovalent
Strong
Puny but important
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Atoms attached via shared electrons in outer shells
H O HH HO
Covalent bonds
CC
C
C C
C
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e.g. CH3-CH3, ethane
Covalent bonds
• stable (strong)
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Covalent bond cleavage
CH3:CH3--> CH3 + CH3
Reactant Products
(Methyl radicals)
(EthaneCH3-CH3)
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Covalent bond cleavage
CH3:CH3--> CH3 + CH3Reactant Products
E = +83 kcal/mol
E is the difference between the energy of reactants and products
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Covalent bond strengths
High bond strength confers stability
0-H 110
C-H 99
C-C 83
C=C 146
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Double bonds restrict rotation
H
H
H
H
Molecule is planar (flat)
e.g. Ethylene (CH2=CH2)
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Covalent bonds are orientated in space
H
H
O104.5 deg
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Covalent Non-covalent
1-5
• 4 kinds.....
Bond strength(kcal/mol) 50-195
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Non-covalent bonds
• Hydrogen bonds
• ionic bonds
• van der Waal's interactions
• hydrophobic interactions
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Non-covalent bonds
• Hydrogen bonds
e.g. in liquid water
oxygen,
hydrogen,
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Hydrogen bond
In liquid water
Each molecule may be H-bonded to
4 others. Bonds are transient
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Typical Hydrogen bonds
H Oor
H N
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Ionic bonds
Non-covalent bonds (cont.)
Result of attraction between + and - charges of ionized atoms
e.g. Na+ Cl-
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Ionic bonds
NaCl dissolved in H2O
Na+ Cl
Note the tight shells of water molecules
Hydrated diameter of ions is important in permeability
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Van der Waals interactions
Non-covalent interactions (cont.)
Due to electron fluxes any atom can become a
transient dipole
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Van der Waals interactions
Non-covalent interactions (cont.)
2 atoms in van der Waals contact
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Van der Waals interactions
Atoms are very close
But not close enough so that their electron shells overlap. If so, they repel each other
You’re disgusting!
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Our next AttractionOur next Attraction
HydrophobiHydrophobiaaStarring a cast of thousandsof greasy characters
Hydrocarbons
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Non-covalent interactions (cont)
Hydrophobic interactions
CH
HCH
HCH
HCH
HCH
HH
Hydrocarbons
CH
HCH
HCH
HH
Combined hydrophobic and van der Waals interactions
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O
NH3 O
CH3
CH2
NH2
CH2
O H C
CH2 C
OCH2 CH2
CH2
CHCH3 CH3
CH3 CH CH2
Bonds at work, H-bonds, ionic
and vd Waals+ hydrophobic bonds
Protein
Protein
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How many water molecules in a teaspoonful?
As many as the teaspoonfuls of water present in the Atlantic Ocean
Trivia Time
A one, a two, a three...
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An everyday protein molecule, hemoglobin
All your hemoglobin alpha chains are
identical with 574 amino acids chained
together in precise sequence
In the past second you have just assembled 400 million million of them
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