TBR electrochemistry

[akimhaneul]

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So I am reading through the electrochemistry chapter of TBR. They say that metals low in oxidation state is a reducing agent whereas metals high in oxidation state are oxidizing agent. I don't quite understand this. I thought metals always give away electrons?


Also, why is catabolism associated with oxidation whereas anabolism is associated with reduction? Is there an intuitive reason for this?

 

[aldol16]

So I am reading through the electrochemistry chapter of TBR. They say that metals low in oxidation state is a reducing agent whereas metals high in oxidation state are oxidizing agent. I don't quite understand this. I thought metals always give away electrons?

Metals can either donate or receive electrons - that's a key function that many students who are not in chemistry miss. It's also the reason why transition metals are so good at catalysis, i.e. doing what organics cannot - they can serve as either electron sinks or electron donors.

The intuitive reason why low-oxidation state metals are reducing agents is because low-oxidation state metals can be oxidized further, i.e. they can give away more electrons. Giving electrons away to something else makes it a reducing agent. Conversely, a metal with a high oxidation state does not want to be oxidized further because of charge buildup and various other factors. In fact, that buildup of charge makes it want to accept electrons to reduce the charge on the metal, making it a better oxidizing agent.

Also, why is catabolism associated with oxidation whereas anabolism is associated with reduction? Is there an intuitive reason for this?

The intuitive reason can be reached by thinking about what anabolism needs. That is, it needs energy - you need energy to do reductive biosynthesis. So where are you getting that energy? Well, you're getting it by taking electrons from somewhere, using them to reduce NAD or NADP or FAD and thus enter into the electron transport chain, which is directly coupled to the proton motive force and ATP synthesis. Thus, the process of taking electrons from a substrate, thereby oxidizing that substrate, and putting them onto electron carriers, thereby reducing those electron carriers, must be associated with anabolism and vice versa.

 

[BerkReviewTeach]

So I am reading through the electrochemistry chapter of TBR. They say that metals low in oxidation state is a reducing agent whereas metals high in oxidation state are oxidizing agent. I don't quite understand this. I thought metals always give away electrons?


Also, why is catabolism associated with oxidation whereas anabolism is associated with reduction? Is there an intuitive reason for this?

aldol16 did a great job explaining this. I want to t add that you should be familiar with the many biological examples of this. Perhaps the most notable is Fe2+ and Fe3+ in blood. Fe2+ is in the lower oxidation state, so it can be oxidized (allowing it to pick up O2). Fe3+ is in the higher oxidation state, so it can be reduced (allowing it to release O2). Metals can take on a wide range of oxidation states, so they can range anywhere from strong reducing agents to strong oxidizing agents.

To add, this is true for some nonmetals too, such as carbon. Carbon can go from -4 (a good reducing agent) to +4 (a good oxidizing agent).