The citric acid cycle contains four 4-carbon dicarboxylic acid...

Question

The citric acid cycle contains four 4-carbon dicarboxylic acids.

b. Arrange them in order from least oxidized to most oxidized.

Accepted Answer

Hello, everyone. And welcome back. Our next question says, succinate, fumarate, malate and oxalacetate are the four di carboxylic acids utilized in a citric acid cycle. List them in order from most oxidized to least oxidized. So let's remind ourselves what this would mean in terms of what's going on in the reactions to convert one to the other. And then let's look at our Krebs A Krebs cycle or Citric acid cycle and think this through. So, of course, on a most basic level, something that's oxidized in a chemical reaction is something that it has lost electrons oxidized, loses electrons. And a way to remember it in sort of shorthand when we look at organic chemicals, is that something that's been oxidized, increases the number of co bonds and or decreases the number of ch bonds without changing the number of CC bonds. So that's kind of our shortcut to remember this. Now, let's look at our creb cycle. So we will go ahead and highlight in blue. Our actually, no, let's highlight it in pink. So it shows up a little better. Our chemicals we're looking at or compounds we're looking at, we have succinate fumarate malate and oxy acetate. We're looking at the end of that citric acid cycle. And let's think about what kinds of reactions are happening before we even need to think about the specifics of the chemical structure. So we know that in a step going from succinate to fumarate, we are reducing F AD, we're giving electrons to F AD. So succinate is losing electrons two F ad. So it gives E minus electrons to F ad when it becomes fumarate. So we know that succinate is getting oxidized to become fumarate. Now, fumarate is a little trickier because fumarate to malate, we're adding a molecule of water. So it's a little trickier. Let's return to that in a minute, then not smell it and then in the process of malate to el acetate. Sorry, I have to go down a little bit because I'm running out of space here. We see that we are reducing a molecule of N AD plus. So a mate is giving electrons two N AD plus. So that's going to be an oxidation as well. I just wrote ox. So let me just highlight in yellow. I've got our pink, I guess I've got succinate, getting oxidized to fumarate, malate, getting oxidized to oxalacetate. So last thing we need to think about is our reaction of fumarate becoming malate with the addition of a molecule of water. Well, what we need to remember is what's happening there is we have AC C double bond in fumarate and then the water is added to that double bond. So in fumarate, the cc double bond when we go into malate becomes ac c single bond and we've added a hydrogen to carbon and we've had an ox carbon one and an oxygen to carbon two in that double bond. So you can see we have increased the number of co bonds here. And actually, to be specific, this is a oh group added to that carbon because there's our water molecule. So we've added an additional co bond. So malate is more oxidized than fumarate because of that. So let's say more oxidized. So you can see we have a progression here by becoming more oxidized, starting with succinate all the way to oxalacetate. And to get technical, we knew that the first and last oxidation reactions because of the um reduction of our F AD and N AD plus. But the specific details in succinate, you have a carbon, carbon, single bond becoming a carbon, carbon double bond. So you've lost some carbon hydrogen bonds. So you've had, that's specifically, it's a more oxidized molecule. We talked about fumarate to mate and then mate to oxy acetate that alcohol group. So the Coh there ccoh has become and let me just redraw that to make it a little less confusing. So we have that alcohol group and it becomes a ketone in oxalacetate. So again, we have an additional co bond and so we've had oxidation again. So what is our order again, of most oxidized to least oxidized, screw this up a little to make some more room. So our most oxidized will be oxy acetate since we've gone through steps of oxidation to get there and then just go down the line. So, oxy acetate to malate to fumarate two s six and eight succinate being the least oxidized. So there we go our answer choice. The dic carboxylic acids involved in the citric acid cycle. In order from most oxidized to least oxidized, we're going backwards in the citric citric acid cycle. Acid cycle. Goodness. That's a tongue twister from most oxidized oxy acetate through malate, fumarate, succinate to least oxidized. So there we go. We've worked through that and I hope to see you in the next video.

The citric acid cycle contains four 4-carbon dicarboxylic acids.
b. Arrange them in order from least oxidized to most oxidized.

Key Concepts

Citric Acid Cycle

Oxidation States

Dicarboxylic Acids

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