Which of the following statements cannot be true about feedback control?

Regulation is achieved by negative allosteric control of an enzyme in the first step. This is true. The end product that we make at the end, some of it will come and attach to the enzyme. It'll attach to the allosteric site, thereby altering the size of the active site so that the substrate can no longer attach. This is negative allosteric regulation, so this is true. The end product affects its own production. Yes, if you're making more than enough of the product and you no longer want to make more, then it could come and attach to the allosteric side of the enzyme and basically deactivate or make that enzyme inactive. So in that way, it is controlling how much of it is being made.

The end product binds irreversibly to the enzyme in the first step. No, it's not irreversible. It is reversible. The end product will attach to the allosteric site and make that enzyme inactive, so it will no longer continue making the product. But, eventually, let’s say you consume all of that product and you want to start making it again. The end product will detach from the allosteric side of the enzyme, and thereby reactivate it so that it can continue to make more product. It's a way of controlling the amount of your end product being formed. When you have too much of it, an overabundance of it, you turn off the enzyme. When you have a low amount of it, you turn the enzyme back on. And this has to do with attaching and detaching to the allosteric side of the enzyme. So here, this is not true. It's not irreversible.

Feedback control can help to save the energy of the cell by shutting down an entire pathway. Yes, it costs a lot of energy to help to make these products. And if you have a ton of a product, what's the point of continuing this series of reactions? You already have enough, so it's good to shut it down until you need some more. So, yes, this would help to save the energy.

So, the only statement here that is not true about feedback control will be option c.