BCH 2333 Lecture Notes - Lecture 1: Stanley Miller, Alexander Oparin, Clathrate Compound
18 Oct 2016
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Biochemistry: Study of life at a chemical level using physical and chemical principles of chemistry and
molecular biology that drive life. These principles allows us to predict certain cases.
These fundamental principles are controlled by chemistry and are shaped by evolution.
Origins of life:
• Earth is over 4.6 x109 years old. Evidence from radiochemical dating of rocks (238U decays to
206P6 –ratio of the two elements can give age of rock), astrophysics and geological
uniformitarianism.
• Oldest fossils are over 3.5 x109 years ago (start of life). Evidence from microfossils. Indirect
evidence so do not know the exact time that life occurred.
Primordial Earth –how could this have led to the formation of life?
• There was a reducing atmosphere which means no O2 was present. O2 can only be present if
something is producing it. Oxygen is too reactive.
• The gases that were probably present in the atmosphere were N2, H2O, CO2, CH4, NH3, SO2.
• No complex organic molecules
• Oparin & Haldane (1920s) proposed Energy + Atmosphere made complex organics. Proposed
energy sources were solar UV, lightning, etc. Tested hypothesis by creating an experiment by
Stanley Miller:
o Set up electrodes to mimic lightning charge. Turned it
up to 80°C and zapped it with charges. What was found was
complex organic molecules that were needed for life to evolve.
o This was consistent with the Oparin & Haldane
hypothesis.
o These molecules were found given there was energy
and time.
• Adenine, which can readily form from HCN (cyanic acid) could have been present in prebiotic
earth. This is required for DNA, RNA, NAD+, CoA, etc.
How does this become life?
Chemical evolution: The simple building blocks combine to make polymers.
• Monomers need to be at high concentration.
• Polymers ultimately become self-replicating.
• RNA Hypothesis: RNA can hold and template its old formation. It can be folded (more
stable than unfolded) and catalytic (essential as it can promote its own replication).
Thought that DNA and proteins improed ad refied hat RNA’s jo as.
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• Self-assel ad opartetalizatio lead to life. This reduced variation due to
environmental changes.
• Life: possesses the properties of repliatio, catalysis and mutability (can be changes).
• Life evolved from inanimate chemicals governed by chemical principle. Fundamental
chemical principles thus govern biochemistry.
Smallest unit of life: the cell
• Two types:
• Eukaryotes: have membrane enclosed nucleus encapsulating their genetic DNA, 10-100um
(fungi, protists, animals, plants)
• Prokaryotes: do not have a nucleus, 1-10um (bacteria, archaea)
Approx. 6000-10 000 biomolecules.
Approx. > 100 000 biomolecules
Approx. 100 000 biomolecules
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How can we hope to understand the role of molecules in a cell?
• Common theme of:
o Biomolecules are polymers
o Limited number of building blocks (approx.. 40)
o Diversity of biopolymers due to order and type of monomers.
o Best characterised are nucleic acids and proteins.
o Amino Acids only have 20 building blocks. Vast majority of chemistry in the cell is done
by proteins.
o Lipids: are held together using ester bonds. Roles: membranes and energy storage.
o Carbohydrates: Monomers held together by glycosidic bonds. Roles: structures and
energy.
Also need Mn, Fe, Co,
Zn, Na, Mg, K, Ca, Cl
*Need to know all 20
amino acids, the five
aromatic bases and the
sugars involved.
Understand building
blocks and the chemical
properties that control
them.
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