Chapter 17, Problem 1FIB

Summary Introduction

Introduction:

The first cells to arise in oceans of Earth were prokaryotes. The genetic material of these cells was not contained within a nucleus. Thus, the cells obtained energy and nutrients by absorbing organic molecules from their environment.

Answer to Problem 1FIB

Correct answer:

In the early atmosphere, there were no oxygen the first cells must have derived energy by anaerobic metabolism of organic molecules. Oxygen was introduced into the atmosphere when some microbes developed the ability to perform photosynthesis and released oxygen as a byproduct. Oxygen was poisonous to many earliest cells, but some cells evolved the ability to use such oxygen in aerobic respiration, which provided far more energy.

Explanation of Solution

There was no oxygen gas in the primitive atmosphere, so cells must have metabolized the organic molecules anaerobically. Thus, anerobic bacteria were the earliest cells. Simpler molecules such as water, and carbon dioxide would still be very abundant.

Eventually, some cells evolved the ability to utilize the energy of sunlight to carry out the synthesis of high energy complex molecules from simplex molecules releasing oxygen as a byproduct.

Oxygen is potentially very dangerous to living organisms as it reacts with organic molecules resulting in their break down. Many anaerobic bacteria of today perish when exposed to oxygen which acts as deadly poison for them. Then the great advance in evolution allowed some organisms to use this oxygen in metabolism. This ability prevented them from chemical action of oxygen and allowed them to channelize the oxygen’s destructive power, through aerobic respiration to generate useful energy in the huge amount for cell.

Conclusion

Oxygen present in the early atmosphere was destruction until evolution of some cells that channelized its power for the aerobic respiration. The amount available to the cell is vastly increased when oxygen is utilized for metabolism of food.