BIOL 2P02 Lecture Notes - Lecture 1: Central Dogma Of Molecular Biology, Hydrogen Fuel, Ionic Bonding
3 May 2018
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Lecture 1: Chapter 1-3: Foundations and Biomolecules 03/05/2018
• What is Life (Chapter 1)
o Must contain
▪ raw materials
• carbon, oxygen, hydrogen
▪ energy
• metabolism, autotrophs,
heterotrophs
▪ envelope
• need own environment i.e. plasma
membrane, mammals maintaining
homeostasis
▪ catalysis
▪ biological info
• repository of info that makes the individual unique -DNA
▪ ability to evolve
o For something to be living it needs to be able to
▪ metabolize, reproduce, pass on info from one generation to generation, react to the
environment
• Molecular Biology
o The study of essential cellular macromolecules
o Involved in everything- cell, agriculture, medicine
o Central dogma-DNA, RNA, protein
o Ultimate goal -> have a functioning cell
• The Central Dogma
o Have DNA, and its able to replicate itself with each cellular divide and pass onto next
generation
o ‘eerse trasriptio doest ork ith the etral doga
o Genome
▪ Not all DNA makes protein
▪ <4% of DNA codes for a functional protein
▪ DNA can be transcribed into RNA ut it doesn’t enode for a protein
• Chemical Bonds
o Types of bonds
▪ definitions
o Strength of bonds
▪ Covalent, ionic -strong
▪ Van der waals -weak
→ RNA → Protei
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o Properties of bonds
• Covalent
o 2 atoms bonded together and share a pair of
electrons filling their outer shell
o Stable
o Polar- unequal sharing
o Nonpolar- equal sharing
o Nonpolar- small electronegativity difference
o Polar- large electronegativity difference
o Partial charges
▪ More electrons, more negativity
• Ionic (salt bridge)
o No partial charges
o Electronegativity is strong enough to strip electrons
• Electronegativity
o Different affinities of the bonded atoms for electrons
o How badly one of the atoms wants the electron for itself
o Electronegativities are measured on the Pauling Scale
▪ If the difference in the 2 atoms is greater than 1.67
then the bond is ionic
▪ If the difference in the 2 atoms is less than 1.67 then
the bond is covalent
▪ Higher the number, the more electronegative it is
▪ Is difference is 0, have non-polar (molecule in red),
no charge
▪ If greater than 0, have polar covalent (molecule in
yellow), B is more electronegative, has partial positive, and A has a partial positive
o Electropositive- more likely to give electrons
o Electronegative-more likely to take electrons
• Separation of positive & negative charges is called electric dipole moment
o Dipole-dipole
o Dipole-ion
• Non-uniform distribution of charge can lead to polar molecules
•
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•
• Ionic bond orientation
o Salt bridges are very important in bio b/c they are flexible and unrestrictive compared to
covalent bonds
o Bond strength- the amount of energy needed to break a bond
▪ In DNA, RNA, etc the ionic bonds are weaker and covalent are stronger
•
• Q1: The difference in electronegativity between two atoms is 1.80, what type of bond do you expect
them to form?
o Polar Covalent
o Non-polar covalent
o Ionic
o Van der waals
•
o Octet rule
o Geometry of bonds is based on how many electrons are present
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find more resources at oneclass.com
