1. Cell Biology
I. Overview
II. Membranes: How Matter Get in and Out of Cells
III. Cellular Respiration
IV. Photosynthesis
V. DNA and Chromosome Structure
VI. Protein Synthesis
VII. Cellular Reproduction
VIII. Origin of Life Hypotheses

2. VIII. Origin of Life Hypotheses
Cell Biology
VIII. Origin of Life Hypotheses
Origin of life hypotheses
Evolutionary Theory

3. A. The Early Earth and Earth History
4.5 bya: Earth Forms
Graviational sorting of materials…heavy to the core, gases released under pressure…

4. The Early Earth and Earth History
- Earliest Atmosphere - probably of volcanic origin
Gases produced were probably similar to those released by modern volcanoes (H2O, CO2, SO2, CO, S2, Cl2, N2, H2) and NH3 and CH4

5. A. The Early Earth and Earth History
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks

6. A. The Early Earth and Earth History
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils
Stromatolites - communities of layered 'bacteria'

7. A. The Early Earth and Earth History
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils
Putative microfossil bacteria from Australia that date to 3.4 by

8. A. The Early Earth and Earth History
bya: Oxygen in Atmosphere
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

9. A. The Early Earth and Earth History
bya: Oxygen
1.8 bya: first eukaryote
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

10. A. The Early Earth and Earth History
bya: Oxygen
1.8 bya: first eukaryote
0.9 bya: first animals
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

11. A. The Early Earth and Earth History
bya: Oxygen
1.8 bya: first eukaryote
0.9 bya: first animals
0.5 bya: Cambrian
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

12. A. The Early Earth and Earth History
bya: Oxygen
1.8 bya: first eukaryote
0.9 bya: first animals
0.5 bya: Cambrian
0.24 bya:Mesozoic
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

13. A. The Early Earth and Earth History
bya: Oxygen
1.8 bya: first eukaryote
0.9 bya: first animals
0.5 bya: Cambrian
0.24 bya:Mesozoic
0.065 bya:Cenozoic
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

14. A. The Early Earth and Earth History
4.5 million to present
(1/1000th of earth history)
bya: Oxygen
1.8 bya: first eukaryote
0.9 bya: first animals
0.5 bya: Cambrian
0.24 bya:Mesozoic
0.065 bya:Cenozoic
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

15. B. The Formation of Biologically Important Molecules
- Oparin-Haldane Hypothesis (1924):
- in a reducing atmosphere, biomonomers would form spontaneously
Aleksandr Oparin
( )
J.B.S. Haldane
( )

16. B. The Formation of Biologically Important Molecules
- Oparin-Haldane Hypothesis (1924):
- in a reducing atmosphere, biomonomers would form spontaneously
- Miller-Urey (1953)
all biologically important monomers have been produced by these experiments, even while changing gas composition and energy sources

17. B. The Formation of Biologically Important Molecules
- Oparin-Haldane Hypothesis (1924):
- in a reducing atmosphere, biomonomers would form spontaneously
- Miller-Urey (1953)
- Sydney Fox polymerized protein microspheres

18. B. The Formation of Biologically Important Molecules
- Oparin-Haldane Hypothesis (1924):
- in a reducing atmosphere, biomonomers would form spontaneously
- Miller-Urey (1953)
- Sydney Fox polymerized protein microspheres
- Cairns-Smith ( ) - clays as templates for non-random polymerization
Murcheson meteorite - amino acids present; some not found on Earth. To date, 74 meteoric AA's.
Szostak - clays could catalyze
formation of RNA's

19. C. Acquiring the Characteristics of Life
Three Primary Attributes:
- Barrier (phospholipid membrane)
- Metabolism (reaction pathways)
- Genetic System

20. C. Acquiring the Characteristics of Life
1. Evolution of a Membrane
- form spontaneously in aqueous solutions

21. A B C D E C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
- problem:
how can pathways with useless intermediates evolve? These represent 'maladaptive valleys', don't they? A B C D E
How do you get from A to E, if B, C, and D are non-functional?

22. A B C D E C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution A B C D E

23. E C. Acquiring the Characteristics of Life Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution
suppose E is a useful molecule, initially available in the env. E

24. E C. Acquiring the Characteristics of Life Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution
suppose E is a useful molecule, initially available in the env.
As protocells gobble it up, the concentration drops. E

25. D E C. Acquiring the Characteristics of Life Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution
Anything that can absorb something else (D) and MAKE E is at a selective advantage... D E

26. D E C. Acquiring the Characteristics of Life Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution
Anything that can absorb something else (D) and MAKE E is at a selective advantage...
but over time, D may drop in concentration... D E

27. C D E C. Acquiring the Characteristics of Life Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution
So, anything that can absorb C and then make D and E will be selected for... C D E

28. A B C D E C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution A B C D E
and so on until a complete pathway evolves.

29. C. Acquiring the Characteristics of Life Evolution of a Membrane
Metabolic Pathways
Solution - reverse evolution
Problem with “Miller-Urey Experiments”
Requires source of continuous environmental energy AND carbon, and continual production of activated nucleotides to drive the reactions to form RNA.
Lightening and other sources of energy do not provide the carbon, and they are unstable and destructively high energy

30. C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
Solution - reverse evolution
Problem with “Miller-Urey Experiments”
What’s Needed:
Continuous flow of energy
Continuous flow of carbon as source of new molecules
Rudimentary catalysts (could be inorganic FeS minerals that are often at the heart of organic catalysts)
“Focusing” products to raise their concentrations to reactive levels

31. C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
Solution - reverse evolution
Problem with “Miller-Urey Experiments”
What’s Needed:
Continuous flow of energy
Continuous flow of carbon
Rudimentary catalysts
“Focusing” products
“Black Smokers”
Very hot – oC, driven by magma in contact with water.
Most stable carbon compound is CO2.
Very unstable, collapsing in decades
Do have lots of FeS compounds but precipitated organics would be blown from chimney.

32. Hydrothermal Vents

33. “White Smokers” of Today
Hydrothermal Vents
“White Smokers” of Today
Mantle rock near spreading centers is exposed to sea water; the olivine (rich in ferrous iron) is oxidized by water in an exothermic reaction, giving off heat and H2.
The warm (60-90oC), H-rich water percolates up and the carbonate minerals precipitate into microporous chimneys.
High flux of carbon and energy is channeled over inorganic catalysts
Thermal currents through pores can concentrate organics 1000 – 106 fold
Vents persist for millennia
500 um

34. H+ The role of a proton gradient:
If the formate (CO2- ) can accept a H+ to balance the charge, it won’t get rid of the electron. If the CO2 is placed in an acidic environment rich in H+, this will tend to happen.
Likewise, if the free H+ is placed in an alkali environment (rich in OH-), it will bind to form stable water. The H2 has reacted with the CO2 irreversibly.
If these fluids are separated by a thin inorganic membrane with FeS minerals, the FeS will draw the electrons from the H2 and transfer them to CO2.
Physical structure of vent drives the synthesis of organics.
These accumulate 1000x
Pore Wall
Seawater percolating through pores:
pH = 6 H+
Percolating from mantle:
pH = 11
OH- H2
FeS
H2O
CO H+  CH2OO
FeS
2e-
2 H+ e-

35. ATP STEP 2: Energy Harvest
The proton gradient can be exploited by protein synthesized organically for Energy Harvest (ATP Synthase).
So, both E harvest AND organic production
ATP

36. C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
Evolution of a Genetic System
- conundrum... which came first, DNA or the proteins they encode?
DNA
RNA (m, r, t)
protein

37. C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
Evolution of a Genetic System
- conundrum... which came first, DNA or the proteins they encode?
DNA
DNA stores info, but proteins are the metabolic catalysts...
RNA (m, r, t)
protein

38. C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
Evolution of a Genetic System
- conundrum... which came first, DNA or the proteins they encode?
- Ribozymes
info storage AND
cataylic ability

39. C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
Evolution of a Genetic System
- conundrum... which came first, DNA or the proteins they encode?
- Ribozymes
- Self replicating molecules
- three stage hypothesis

40. Stage 1: Self-replicating RNA evolves

41. (REPLICATION ENZYMES)
Stage 1: Self-replicating RNA evolves
RNA
m- , r- , and t- RNA
PROTEINS
(REPLICATION ENZYMES)
Stage 2: RNA molecules interact to produce proteins... if these proteins assist replication (enzymes), then THIS RNA will have a selective (replication/reproductive) advantage... chemical selection.

42. (REPLICATION ENZYMES)
DNA
Reverse transcriptases
m- , r- , and t- RNA
PROTEINS
(REPLICATION ENZYMES)
Stage 3: Mutations create new proteins that read RNA and make DNA; existing replication enzymes replicate the DNA and transcribe RNA.

43. Can this happen? Are their organisms that read RNA and make DNA?

44. Can this happen? Are their organisms that read RNA and make DNA?
yes - retroviruses....

46. (REPLICATION ENZYMES)
DNA
m- , r- , and t- RNA
Already have enzymes that can make RNA...
PROTEINS
(REPLICATION ENZYMES)
Stage 3: Mutations create new proteins that read RNA and make DNA; existing replication enzymes replicate the DNA and transcribe RNA.

47. (REPLICATION ENZYMES)
DNA
m- , r- , and t- RNA
Already have enzymes that can make RNA...
PROTEINS
(REPLICATION ENZYMES)
Stage 3: Mutations create new proteins that read RNA and make DNA; existing replication enzymes replicate the DNA and transcribe RNA.

48. (REPLICATION ENZYMES)
This is adaptive because the two-step process is more productive, and DNA is more stable (less prone to mutation).
DNA
m- , r- , and t- RNA
PROTEINS
(REPLICATION ENZYMES)
Stage 4: Mutations create new proteins that replicate the DNA instead of replicating the RNA...

49. (REPLICATION ENZYMES)
This is adaptive because the two-step process is more productive, and DNA is more stable (less prone to mutation).
DNA
And that's the system we have today....
m- , r- , and t- RNA
PROTEINS
(REPLICATION ENZYMES)
Stage 4: Mutations create new proteins that replicate the DNA instead of replicating the RNA...

50. D. Summary:
STEPS REQUIRED FOR THE SPONTANEOUS, NATURAL FORMATION OF LIFE, and the evidence to date:
1. Spontaneous synthesis of biomolecules - strong evidence; Miller-Urey experiments.
2. Polymerization of monomers into polymers (proteins, RNA, sugars, fats, etc.) - strong evidence;  Fox and Cairns-Smith experiments.
3. Formation of membranes - strong evidence; behavior of phospholipids in solution.
4. Evolution of metabolic systems - reasonable hypotheses, and genetic similarity in genes involved in particular pathways (suggesting gene duplication and subsequent evolution of new genes and elaboration of existing pathways)
5. Evolution of a genetic system - a reasonable hypothesis and significant corroborating evidence that it could happen. But no experimental evidence of the process evolving through all three steps.
6. How did these three elements (membrane, metabolism, genetic system come together?) a few untested hypotheses.