Nelson's second chapter generally talks about the inner workings of a cell: describing each component and how it works to fit the big picture. Reflecting on this, I am reminded of the concept of engines. The engine works by consuming fuel and producing energy for useful work. Each cell, for example in an organ, works in harmony to produce something beneficial to the body, but it requires energy from an external source like food to function efficiently.
With respect to the chapter, cells contain small systems within itself to function. As Martin and Wendy have discussed/shown in the videos, kinesin plays a huge role in the transport of vesicles within the the cell. Kinesins work with the alternating phosphorylation of ATP and re-phosphorylation of ADP attached to the heads. The energy released from the phosphorylation of ATP on the kinesin head detached one of the kinesin head and uses the energy to move the head forward the microtubule path and the ADP gets re-phosphorylated to attach the head to the microtubule which allows the other head to move forward.
Now comparing this to the workings of the engine, the system similarly undergoes three stages of the four stroke cycle: intake (fuel enters), power (fuel is burnt) and exhaust (exhaust out) stroke. The intake stroke is similar to the step when an enzyme attaches to phosphorylate ATP as "fuel" is about to enter the head. The power stroke could then be the "spark" produced when ATP is phosphorylated which enables the head to move. The exhaust stroke is alike to the ADP as the energy produced from the previous process is consumed. But unlike the engine, the cell has a way of recycling the energy rather than using new fuel to produce work.
This is just a comparison and is very open to criticism, but I'd like to think of it that way as to keep the biological systems grounded to physical theories. Thoughts?
With respect to the chapter, cells contain small systems within itself to function. As Martin and Wendy have discussed/shown in the videos, kinesin plays a huge role in the transport of vesicles within the the cell. Kinesins work with the alternating phosphorylation of ATP and re-phosphorylation of ADP attached to the heads. The energy released from the phosphorylation of ATP on the kinesin head detached one of the kinesin head and uses the energy to move the head forward the microtubule path and the ADP gets re-phosphorylated to attach the head to the microtubule which allows the other head to move forward.
Now comparing this to the workings of the engine, the system similarly undergoes three stages of the four stroke cycle: intake (fuel enters), power (fuel is burnt) and exhaust (exhaust out) stroke. The intake stroke is similar to the step when an enzyme attaches to phosphorylate ATP as "fuel" is about to enter the head. The power stroke could then be the "spark" produced when ATP is phosphorylated which enables the head to move. The exhaust stroke is alike to the ADP as the energy produced from the previous process is consumed. But unlike the engine, the cell has a way of recycling the energy rather than using new fuel to produce work.
This is just a comparison and is very open to criticism, but I'd like to think of it that way as to keep the biological systems grounded to physical theories. Thoughts?
Hi Wayne.
ReplyDeleteI disagree with your comment that "...unlike the engine, the cell has a way of recycling the energy rather than using new fuel to produce work."
I completely agree that ADP is recycled by the cell, but this does not mean that the cell no longer has need for an external fdel source. Some external source is always required for the energy which is used to rephosphorylate ADP (thermodynamics tells us this, otherwise we would be getting work for free, without any temperature gradients, etc.).
I suppose it's a little more like an electric car: it always uses the same battery, but external power is required to keep the battery charged.
James
Remember: one person's harmonious peace is another's state of armed detente! Order does not imply harmony: there is a case to be made that the order manifest in multicellular organisms is the result of intercellular war fought to a detailed standstill. -Seth
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