The metabolic pathways of organism living today evolved over a long period of time- undoubtedly in a step wise fashion because of their complexity. Considering everything you have learned to date about the evolution of life on Earth, put the following in the order in which they might have evolved, and provide an explanation for your arrangement.
__prokaryotes capable of performing Krebs cycle
__eukaryotes capable of performing Krebs cycle
__prokaryotes capable of performing electron transport
__eukaryotes capable of performing electron transport
__prokaryotes capable of performing glycolysis
__eukaryotes capable of performing glycolysis
__prokaryotes capable of performing photosynthesis
__eukaryotes capable of performing photosynthesis
I have prokaryrotes in 1-4 in which glycolysis, photosynthesis, electron transport, and krebs. I just do not know how to arrange it for the eukaryotes.
My explanation for these pathways in prokaryotes is glycolysis does not require Oxygen. Photosynthesis requires electron transport which cannot occur in the absence of Oxygen. Krebs cannot occure without NAH_ so Electron tranposrt has to come before it because ET converts NADH to NAD+
I was thinking of Eukaryotes photosynthesis as the last one because according to endosymbiosis, eukaryptes would have engulf chloroplasts after mitochondria because many eukaryotes have mitochondria and not chloroplasts.
Based on the information you have provided, you have correctly arranged the order of prokaryotic pathways. Now let's consider the evolution of these pathways in eukaryotes.
1. Eukaryotes capable of performing glycolysis: Glycolysis is a fundamental metabolic pathway that produces energy from glucose. It is found in both prokaryotes and eukaryotes. Since glycolysis is an ancient pathway that doesn't require specialized compartments or organelles, it is likely to have evolved early in the history of life. Therefore, it can be placed as the first step in the evolution of eukaryotic metabolism.
2. Eukaryotes capable of performing electron transport: Electron transport is a process that uses an electron transport chain to generate energy in the form of ATP. While prokaryotes can perform electron transport, eukaryotes have more complex and efficient systems for this process. The endosymbiotic theory suggests that eukaryotic cells evolved from a symbiotic relationship between prokaryotes, specifically when an ancient eukaryote engulfed a prokaryote capable of performing electron transport (which eventually became the mitochondria). Therefore, the evolution of eukaryotes capable of performing electron transport likely occurred after glycolysis.
3. Eukaryotes capable of performing the Krebs cycle: The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid cycle, is an essential pathway for extracting energy from organic molecules. The Krebs cycle requires several enzymes and specialized compartments within the cell, such as the mitochondria. Considering that eukaryotes acquired the ability to perform electron transport before the Krebs cycle (due to the endosymbiotic origin of mitochondria), it is logical to place eukaryotes capable of performing the Krebs cycle after those capable of performing electron transport.
4. Eukaryotes capable of performing photosynthesis: Photosynthesis is a complex metabolic pathway that involves the conversion of light energy into chemical energy. Photosynthetic eukaryotes have specialized structures called chloroplasts, which likely originated from the engulfment of photosynthetic prokaryotes. Since the evolution of chloroplasts is thought to have occurred through endosymbiosis after the evolution of mitochondria, it is reasonable to place eukaryotes capable of performing photosynthesis as the last step in the evolution of these metabolic pathways.
Therefore, the final arrangement for eukaryotes would be:
1. Eukaryotes capable of performing glycolysis
2. Eukaryotes capable of performing electron transport
3. Eukaryotes capable of performing the Krebs cycle
4. Eukaryotes capable of performing photosynthesis
Remember, this is a hypothetical arrangement based on our understanding of the evolution of life on Earth. The actual timeline and sequence of these events may be more complex and still subject to ongoing scientific research.