dude101010
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explain why irreversible steps are important in metabolic pathways are important?

I understand that an irreversible step is when a product cannot go back in a pathway but I don't know how to answer this question.

thanks for the help.
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OxFossil
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I have no idea what your exam board is looking for but here's my thoughts

1. There is no such thing as an irreversible metabolic path or step - any step can, in theory, be reversed provided enough energy is put in to reversing it. This is generally true of most chemical reactions

2. However, metabolism is purposeful. It aims, generally, to produce some useful metabolite. Typically, this involves either converting bond energy contained in energy-rich compounds (such as ATP) into energy that can be used for other purposes (driving other biochemical reactions), or else producing certain products that are in deficit from others that are in excess (for example converting a hormone precursor into the active form).

3. To ensure the metabolic process goes in the right direction, it helps to include steps that would require big energy inputs to reverse (i.e. which are effectively irreversible). A cell or system which is in total equilibrium (i.e where the reactions are in equilibrium, going equally in both directions) is a dead cell.

Does that help any?
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macpatgh-Sheldon
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Hi,

In some physiological situations, a toxic product might be converted into something less toxic or even safe - then in this case, you want the detoxification process to be irreversible, so that you do not go back to the toxic moiety e.g. the liver is the main site where these processes occur, and some of the reactions brought about by the cytochrome P450 system are irreversible.

A different situation might be when the product of a reaction is crucial for well-being or survival, or where the product is the substrate for the next step, and therefore the system cannot afford to have it reconverted to its precursor.

Technically, you could also give an example of such a reaction that is disadvantageous and non-physiological kinda, which could be seen as "important" e.g. the binding of carbon monoxide to haemoglobin (Hb) to produce carboxyhaemoglobin is irreversible, and can ultimately deplete enough Hb to cause severe symptoms or death.

M
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dude101010
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(Original post by OxFossil)
I have no idea what your exam board is looking for but here's my thoughts

1. There is no such thing as an irreversible metabolic path or step - any step can, in theory, be reversed provided enough energy is put in to reversing it. This is generally true of most chemical reactions

2. However, metabolism is purposeful. It aims, generally, to produce some useful metabolite. Typically, this involves either converting bond energy contained in energy-rich compounds (such as ATP) into energy that can be used for other purposes (driving other biochemical reactions), or else producing certain products that are in deficit from others that are in excess (for example converting a hormone precursor into the active form).

3. To ensure the metabolic process goes in the right direction, it helps to include steps that would require big energy inputs to reverse (i.e. which are effectively irreversible). A cell or system which is in total equilibrium (i.e where the reactions are in equilibrium, going equally in both directions) is a dead cell.

Does that help any?
thanks for the help! i am doing Scottish highers, by the way
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