Date/Time
Date(s) - 04/09/2024
10:30 am - 11:30 am

Location
Physics and Astronomy Department

ABB 102

Speaker: Dr. Paul Higgs

Title: Professor
McMaster University
Dr. Higgs Profile Link

Title: How Did the First Protocells Work?

Abstract:
It is often said that the origin of life requires three things: a replication mechanism, a metabolism, and a compartment. We ask what kind of chemical reaction system is required to constitute a metabolism that can sustain itself inside a protocell. It is important that the metabolism should happen in the cell but not outside. We call this combination of active internal state and inactive external state “Inside-Outside Stability”. We show that this is possible when the reaction network is second order in the catalyst concentration, but not when it is first order. Theoretical models of second order reaction networks can be written down, but we do not know of real chemical systems that fit these schemes. This is an important problem for theories that propose metabolism came first. We then consider non-enzymatic templating of RNA oligomers, and we show that this is a second order system with the required properties to support a protocell. A supply of activated monomers keeps the system out of equilibrium. It is not necessary to have another (unknown) metabolic reaction system to drive templating. In this picture, templating of random oligomers is the origin of both metabolism and replication. ATP later becomes central to modern metabolism because it was previously used to drive RNA synthesis. It is well-known that biomolecules are homochiral (only one of the left and right-handed enantiomers is used). Homochirality arises from asymmetric autocatalysis. Molecules of each enantiomer catalyze formation of more molecules of the same enantiomer. Reaction systems with this property show spontaneous chiral symmetry breaking. We consider symmetry breaking reactions related to either amino acid synthesis or RNA synthesis. If these reactions occur in a protocell, the cell can become homochiral, while the outside remains racemic (as is observed in nature). Thus, the reaction that constitutes the metabolism can also be the reaction that causes chiral symmetry breaking.