Cell Biology I. Overview II. Membranes: How Matter Get in and Out of Cells III. DNA, RNA, and Chromosome Structure IV. Protein Synthesis V. Origin of Life.

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Presentation transcript:

Cell Biology I. Overview II. Membranes: How Matter Get in and Out of Cells III. DNA, RNA, and Chromosome Structure IV. Protein Synthesis V. Origin of Life Hypotheses

Cell Biology I. Overview II. Membranes: How Matter Get in and Out of Cells III. DNA, RNA, and Chromosome Structure IV. Protein Synthesis V. Origin of Life Hypotheses Origin of life hypotheses Evolutionary Theory

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

A.The Early Earth and Earth History - Earliest Atmosphere - probably of volcanic origin Gases produced were probably similar to those released by modern volcanoes (H 2 O, CO 2, SO 2, CO, S 2, Cl 2, N 2, H 2 ) and NH 3 and CH 4

A. The Early Earth and Earth History 4.5 bya: Earth Forms4.0 bya: Oldest Rocks

A. The Early Earth and Earth History 4.5 bya: Earth Forms4.0 bya: Oldest Rocks3.4 bya: Oldest Fossils Stromatolites - communities of layered 'bacteria'

A. The Early Earth and Earth History 4.5 bya: Earth Forms4.0 bya: Oldest Rocks3.4 bya: Oldest Fossils Putative microfossil bacteria from Australia that date to 3.4 by

A. The Early Earth and Earth History 4.5 bya: Earth Forms4.0 bya: Oldest Rocks3.4 bya: Oldest Fossils bya: Oxygen in Atmosphere

A. The Early Earth and Earth History 4.5 bya: Earth Forms4.0 bya: Oldest Rocks3.4 bya: Oldest Fossils bya: Oxygen 1.8 bya: first eukaryote

A. The Early Earth and Earth History 4.5 bya: Earth Forms4.0 bya: Oldest Rocks3.4 bya: Oldest Fossils bya: Oxygen 1.8 bya: first eukaryote 0.9 bya: first animals

A. The Early Earth and Earth History 4.5 bya: Earth Forms4.0 bya: Oldest Rocks3.4 bya: Oldest Fossils bya: Oxygen 1.8 bya: first eukaryote 0.9 bya: first animals 0.5 bya: Cambrian

A. The Early Earth and Earth History 4.5 bya: Earth Forms4.0 bya: Oldest Rocks3.4 bya: Oldest Fossils bya: Oxygen 1.8 bya: first eukaryote 0.9 bya: first animals 0.5 bya: Cambrian0.24 bya:Mesozoic

A. The Early Earth and Earth History 4.5 bya: Earth Forms4.0 bya: Oldest Rocks3.4 bya: Oldest Fossils bya: Oxygen 1.8 bya: first eukaryote 0.9 bya: first animals 0.5 bya: Cambrian0.24 bya:Mesozoic0.065 bya:Cenozoic

A. The Early Earth and Earth History 4.5 bya: Earth Forms4.0 bya: Oldest Rocks3.4 bya: Oldest Fossils bya: Oxygen 1.8 bya: first eukaryote 0.9 bya: first animals 0.5 bya: Cambrian0.24 bya:Mesozoic0.065 bya:Cenozoic 4.5 million to present (1/1000th of earth history)

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 ( )

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

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

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

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

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

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways - problem: how can pathways with useless intermediates evolve? These represent 'maladaptive valleys', don't they? ABCDE How do you get from A to E, if B, C, and D are non-functional?

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways - Solution - reverse evolution ABCDE

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways - Solution - reverse evolution E suppose E is a useful molecule, initially available in the env.

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways - Solution - reverse evolution E suppose E is a useful molecule, initially available in the env. As protocells gobble it up, the concentration drops.

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways - Solution - reverse evolution E Anything that can absorb something else (D) and MAKE E is at a selective advantage... D

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways - Solution - reverse evolution E Anything that can absorb something else (D) and MAKE E is at a selective advantage... but over time, D may drop in concentration... D

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways - Solution - reverse evolution E So, anything that can absorb C and then make D and E will be selected for... DC

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways - Solution - reverse evolution ABCDE and so on until a complete pathway evolves.

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways 3.Evolution of a Genetic System - conundrum... which came first, DNA or the proteins they encode? DNA RNA (m, r, t) protein

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways 3.Evolution of a Genetic System - conundrum... which came first, DNA or the proteins they encode? DNA RNA (m, r, t) protein DNA stores info, but proteins are the metabolic catalysts...

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways 3.Evolution of a Genetic System - conundrum... which came first, DNA or the proteins they encode? - Ribozymes info storage AND cataylic ability

C. Acquiring the Characteristics of Life 1.Evolution of a Membrane 2.Metabolic Pathways 3.Evolution of a Genetic System - conundrum... which came first, DNA or the proteins they encode? - Ribozymes - Self replicating molecules - three stage hypothesis

RNA Stage 1: Self-replicating RNA evolves

RNA Stage 1: Self-replicating RNA evolves 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. 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. m-, r-, and t- RNA PROTEINS (REPLICATION ENZYMES) DNA Reverse transcriptases

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

yes - retroviruses....

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

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

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

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

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.