Is there a hemi in there?

Combo fuel/engine/chassis units (also known as trucks) perform work in moving objects from point to point against an opposing force - gravity. Affectionados say that trucks are not all alike - they vary in their capacity to perform work, on a power per unit weight basis (horsepower per pound of truck). Indeed, a given model may change (perhaps from one year to another) with respect to its horsepower per pound capacity in response to a signal (say from the consumer to the manufacturer).

Enzymatic proteins can be like trucks.

These combo fuel/engine/pump units are integral within the cell walls of living organisms. They perform work by making a conformational change to move a solute ion through the cell wall against an opposing force - the ionic concentration gradient for that particular solute. Specifically, the Na+/K+ - ATPase pump transfers sodium ions out through the cell wall, and transfers potassium ions back in, using energy from a fuel source - adenosine triphosphate (ATP). ATP attaches to an active site on the protein molecule and undergoes a chemical reaction with water to produce adenosine diphosphate (ADP). Energy is released in the hydrolysis reaction. These pumps are fundamental to the cell's very existence because they remove and replace ions that leak in and leak out of the cell respectively, thus maintaining the ionic balance across the cell wall and therefore the cell electrical potential. Maintaining the ionic balance across the cell wall is also vital to balancing the osmotic pressure on either side of the cell wall, or water could alternatively flow into or out of the cell causing its destruction.

When fish move from the fresh water of a hatchery or stream to the salt water of an aquaculture site or the open ocean shortly after the parr-smolt transformation, the fish and its cells are exposed to huge changes in osmolarity. The activity (power per unit weight of protein) of the enzymatic protein pumps in the gill cell walls of the young fish must be sufficient by that time to meet the increased demand for work to balance the salt concentrations on either side of the cell wall.

In fact, the power of the pumps in gill cells begins to increase during the parr-smolt transformation, prior to transfer to salt water, in response to a signal (the appearance of a hormone).

One of RPC's clients this year was a supplier of special feed ration systems that promote a uniform parr-smolt transformation within a fish population so that the fish are all physiologically ready for salt water at the same time.

To assist the client in applying the technology to New Brunswick's aquaculture industry, RPC developed a method of measuring the activity of the pumps in gill cells. We can determine if the fish are physiologically ready for the move to salt water - too early can cause excessive mortality (pumps too weak), too late can cause excessive grilse production in some stocks (over-production of signal hormones.).

One could say RPC tests that the right power level is achieved at precisely the right time for the enzymatic proteins in the gill cells in all the fish to cope with a greater workload. To maintain our truck analogy, we might even express it as having the right nanohorsepower per pound of protein!

 

 

 

 

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