In Chapter 8, we saw that ATP is the currency of the cell, powering almost all t
ID: 197379 • Letter: I
Question
In Chapter 8, we saw that ATP is the currency of the cell, powering almost all the work carried out in a typical cell. In almost all eukaryotes and aerobic prokaryotes, the majority of this ATP is synthesized from the flow of stored hydrogen ions (protons) in the form of a proton gradient. This week’s forum will explore the universality of proton gradients and provide insight into the role they may have played in the origin of life itself and why, despite their incredible biochemical virtuosity, prokaryotes have failed to develop the complex morphology (multicellularity) observed for eukaryotic cells . Read the article Why Are Cells Powered by Proton Gradients, and answer the questions that follow. ----> LINK ; https://www.nature.com/scitable/topicpage/why-are-cells-powered-by-proton-gradients-14373960
1. (a) Explain how “natural” proton gradients could have arisen at ancient hydrothermal vents. Be sure to include in your response the source of the protons. (b) Do those same “natural” gradients exist today at hydrothermal vents – why or why not?
2. From analysis of Figure 4, explain the meaning of the Figure Legend, “Why chemistry is not enough”.
3. What explanation does the paper provide as to why prokaryotic cells have shown little tendency to develop the morphological complexity observed for eukaryotic cells?
4. Speculating is a fun part of science. Many of the hypotheses put forth in this paper are highly speculative. For example, little data exists to support the hydrothermal vent origin of proton gradients. Based on our class discussions, either propose another possible origin for proton gradients, or propose a question on a point or aspect of the origin that you find unclear or confusing.
Explanation / Answer
CO2 forms carbonic acid in solution which makes the ocean acidic. This acidity would have been very high as compared to the hydrothermal vents upto four times, some billions years ago. This lead to the formation of natural proton gradient across the vent membranes and could have led to the evolution of life. In the present times, the acidity of the oceanic water is low as it was in the past, due to which the gradient is not sharp.
The study of chemisty is based on stoichiometry, which means that the equations in the chemisty can be balanced. However, aerobic respiration cannot be balanced. Therefore, chemistry by itself cannot explain the entire process.
The absence of mitochondrial genome in the prokaryotes, reduced their capability to have control for the energy expenditure required for the complex set of functioning that are normally present in eukaryotes.