D.1b: Origin of Life: RNA World
25/08/2013 § 1 Comment
I know we talked about this in class a little bit – RNA. We assume that the mechanism of life had to start somewhere and one possibility is RNA itself because of two specific properties: self-replication and catalysis. We know that RNA molecules can perform self-replication because they act as the templates that replicate DNA strands during protein synthesis or simple replication. The RNA molecules’ ability to build these templates also gives them the ability to replicate themselves. Also during protein synthesis, RNA molecules can create the peptide bond formation in the ribosome, which is a catalysis of a reaction, meaning that RNA’s ability to catalyse chemical reactions could definitely have assisted in the evolution of life.
Also, since membranes were needed to form the first cells, phospholipids naturally grouped together to form the bilayers we know of now. These phospholipids, called protobionts, allowed for an internal environment to develop.
DATA BASED QUESTIONS
RNA, page 309
1. In experiment A, outline the effect of exposing the labelled empty vesicles to vesicles containing RNA.
As more time passed, the empty vesicles in experiment A would decrease exponentially in relative surface area. Between 0 and ~18 minutes is the steepest drop and from there the drop moves at a slower rate.
2. In experiment B, outline the effect of exposing labelled vesicles containing RNA to unlabelled empty vesicles.
Contrasting to experiment A, when the labelled vesicles were escaped to unlabelled empty vesicles, the surface area of the vesicles containing RNA grew exponentially. The steepest growth runs from 0 and ~16 minutes and grows at a slower rate afterwards.
3. Evaluate the conclusion from these experiments that vesicles containing RNA can take membrane material from vesicles that do not contain RNA.
Because of osmosis, the membrane-encased environment within the vesicles that contain RNA will allow its water to move from inside it to the empty vesicles, which is why in experiment A, the RNA-filled vesicles lose their relative surface area, and why the vesicles with RNA in experiment B gain surface area. The water moves between the membranes.
4. Suggest why vesicles containing RNA would become more common.
Vesicles that have RNA would survive better under multiple circumstances and the vesicles that don’t would then die off as a result of natural selection.