Primitive bio-chemistry to molecular biology ASTR 3300 Guest Lecture by Bonnie Meinke September 2,...
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Transcript of Primitive bio-chemistry to molecular biology ASTR 3300 Guest Lecture by Bonnie Meinke September 2,...
Primitive bio-chemistry to
molecular biology
Primitive bio-chemistry to
molecular biologyASTR 3300
Guest Lecture by Bonnie MeinkeSeptember 2, 2009
ASTR 3300Guest Lecture by Bonnie Meinke
September 2, 2009
RNA worldRNA world
Chicken and egg paradox: how could one of the key molecules (DNA, RNA, and protein enzymes) have existed without the other two?
Discovery in the mid-1980s: RNA has catalysts (ribozymes), which means a simpler RNA world may preceded the DNA and protein world
RNA worldRNA world
evidence for an early RNA world:
RNA nucleotides are more readily synthesized than DNA nucleotides
DNA could have evolved from RNA and taken hold because of its greater stability
RNA must have evolved before proteins because proteins cannot replicate in absence of RNA
RNA worldRNA worldsimple RNA organisms eventually began transcribing DNA
DNA is a more efficient replicator, so it outcompeted RNA via natural selection
viruses are parasites made of nucleic acid encased in protein coats
once inside a host organism, viruses hijack its chemical energy and replicates itself
retroviruses reverse cellular processes by transcribing RNA into DNA, which instructs the cell to produce more viral RNA
HIV
HPV
RNA and retroviruses
RNA and retroviruses
Primitive Biochemistries
Primitive Biochemistries
Organisms require energy source
Organisms that create organic matter from energy and inorganic substances are called autotrophs
What are the energy sources autotrophs utilize?
Primitive Biochemistries
Primitive Biochemistries
Organisms require energy source
Organisms that create organic matter from energy and inorganic substances are called autotrophs
What are the energy sources autotrophs utilize?
Light
Chemicals
Energy SourcesEnergy SourcesMost important energy source for Earth is the sun: Photosynthesis
uses light energy to produce sugars and oxygen from water and carbon dioxide
nCO2 + nH2O + energy (CH2O)n + nO2
Mid-ocean hydrothermal vents: chemosynthesis
Chemical energy is utilized in this process. Superheated water dissolved minerals in rock, which organisms living near such vents use to create organic compounds.
MetabolismMetabolism• Two most common metabolisms on Earth today:
• Fermentation
• Carbohydrate glucose CO2 + ethanol/ lactic acid + energy
• Only extracts 2 phosphate bonds’ worth of energy
• Respiration
• (CH2O)n + nO2 nCO2 + H2O + energy
• Extracts a whopping 36 phosphate bonds’ worth of energy!
• Much more efficient than fermentation
Molecular phylogenyMolecular phylogeny
Top-down approach to extrapolate origin of life (~ 4 Ga) from current biosphere
Phylogenetic trees show that evolution allows life to build on what has worked
Method involved in constructing a tree involves examining similar molecules in different organisms and comparing to trace a common ancestor
Phylogenic tree from ribosomal RNA
Phylogenic tree from ribosomal RNA
Life broken into 3 domains
Bacteria
Archaea
Eukarya
Tree of LifeTree of LifeThermophiles and hyperthermophiles lie near roots of branches - life has evolved from high to low temperature environments
Organisms near roots also use energy source other than light
This means last common ancestor was likely a heat-loving chemosynthetic organism such as those in hydrothermal vents today (thermophile - to be discussed week after next)