1.All living organisms alive today are assumed to have evolved from some one-cel
ID: 147086 • Letter: 1
Question
1.All living organisms alive today are assumed to have evolved from some one-celled ancestor that lived about four billion years ago and has been called the Last Universal Common Ancestor or LUCA. LUCA has been extinct for a long time but evolutionary biologists have hypothesized as to what it was like. Given the characteristics of modern prokaryotic and eukaryotic organisms, what cellular characteristics would you suggest that LUCA had? What type of cellular respiration might LUCA have used? Why?
2. Why is water so essential for biological life? Provide examples as to how water is used in living systems.
Explanation / Answer
Characteristics of LUCA-
Circular DNA floating in the cytoplasm.
Its genetic material can be DNA or RNA.
It could survive harsh conditions like hot lava etc.
cytoplasm was enclosed by a lipid membrane.
Has ion transporters.
Cells multiply by cell division.
It reduces CO2 and oxidizes H2.
ATP served as an energy intermediate.
Ribosomes were the 70S.
Cellular respiration used-
It was anaerobic, CO2 fixing, H2 dependent with acetyl coenzyme pathway. It has FeS clusters.
2. Water is a universal solvent. Cells have cytoplasm in which all the metabolic reactions take place.
Water is used in photosynthesis to generate oxygen. Water is used by animals for all the processes in the body. The human body is made up of 70% water.
There is 20% water in bone cells and 85% in the brain.
There are many reactions like hydrolysis of fats and proteins. These reactions require water for breaking down large substances. Proteins are hydrolyzed into amino acids to generate ATP.
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