Question

1. An analogy of a rechargeable battery can be used to describe ATP. Explain this analogy in detail and evaluate whether this analogy is accurate.

2. RuBisCo is used by almost all photoautotrophs. It is believed to be the most important enzyme in the biosphere by many scientists. Defend or refute this claim. Be detailed.

3. Imagine you are a genetic engineer who is interested in plants as a method to fight climate change. What reactions and molecules in photosynthesis should you target? Explain.

Answer 1

1. ATP is the universal cellular currency in all living organisms.
Anabolic reactions are mediated by ATP hydrolysis.
Catabolic reactions are coupled to produce ATP
ATP -----> ADP + Pi
Organisms only utilize the hydrolysis of ATP to drive anabolic reactions. They do not breakdown the ATP molecule. Hence, ADP and Pi can be reused to produce ATP from coupled exergonic reactions. This is similar to rechargeable batteries which can be reused many times.

2. The given statement is true.
Rubisco is the most abundant protein on earth. It is present in all phototropic organisms. It catalyzes the carboxylation step during the light-independent reactions. i.e. it is directly responsible for the utilization/fixing of CO2 into carbohydrates.

3. A good target molecule would be Rubisco.
The Rubisco enzyme exhibits dual activity. It acts as a carboxylase to produce glucose via the C3 cycle. It can act as an oxygenase to waste metabolic energy via photorespiration.
Climate change is due to elevated atmospheric CO2 levels. We can engineer the modified Rubisco enzyme in such way that it can efficiently utilize CO2.