Coenzymes in Metabolism - Video Tutorials & Practice Problems
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concept
Coenzymes in Metabolism Concept 1
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Now, co enzymes are important in metabolic reactions. We're gonna say the driving force of metabolism is the oxidation of molecules. In order to release energy, we're gonna say this is accomplished by coenzyme cycling between their oxidized and reduced forms. Now, here we're gonna say the reduced forms act as electron carriers that carry energy that is ultimately pass bonds of A TP. If we take a look here, we're going to say that we have substrate A and to show its reduced form. And remember reduction here is in terms of having hydrogen or not gaining hydrogen or not. So this substrate A would be the reduced form of it to show that we just show a hydrogen on it. Here, it undergoes oxidation where it will lose its hydrogen. So if this thing here is losing its hydrogen, where is it going? Well? If it's losing its, it's handing it over to the co enzyme here, the co enzyme in its oxidized form doesn't have it, but it gets reduced in this process. And now it's in its reduced form. The coenzyme is the carrier of the electrons in the form of this hydrogen component that hydrogen is not only h it's the electrons in the bond with it that reduced form can then take itself become oxidized back to its oxidized form. When it becomes oxidized, it's basically handing over its H to substrate b substrate games that age. And now we have it reduced form here. So basically, uh these co enzymes are kind of acting as a carrier. They're taking electrons from one molecule and hang them over to another one. Later on this again, ultimately is to help us to create lots and lots of a TP. At the end, as we progress through our topics, we'll see how this exactly is done.
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example
Coenzymes in Metabolism Example 1
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Here in this example, it says, consider the reaction given below and correctly identify the oxidizing agent. So remember your oxidizing agent is what's been reduced and what's been reduced has gained electrons or in this case hydrogen with those electrons. And remember when we're looking at oxidizing agent or reducing agent, those are the reactants. We look at the product side to see where the electrons went. But then we look back at the reactant to determine, OK, this was reduced and this was oxidized. If we take a look here, we have mate as a reactant. And then over here we have a solo acetate here. We have N ad positive, which is a coenzyme. But if we look n ad positive in this form as a reactant, but then over here, it's gained a hydrogen and not only a hydrogen but electrons, that's why it's neutral. Now, so we're gonna say N ad plus gained electrons and hydrogen. And so it was reduced and therefore, it's the oxidizing agent. Now, this question doesn't ask this, but we could also say that mate had an alcohol group here. His alcohol group was oxidized into a heat to portion here, remember we learned this several chapters ago that alcohols can be oxidized into carbon neal group C double 10. So this thing was oxidized. Therefore, with the reducing agent, the question doesn't ask this, but we're just trying to cover everything and see the difference. But again, for this particular one, the oxidizing agent would be N AD plus.
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concept
Nicotinamide Adenine Dinucleotide Concept 2
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So nicotinamide, adenine di nucleotide or N AD we're gonna say here, the nicotinamide group of N AD plus is the site of reduction that is seeking to become neutral. So we wanna lose that charge. If we look here at N AD plus, it's oxidized form nitrogen. Remember when it makes for bonds, it's positively charged. We're trying to remove this positive charge here. We're gonna say the reduction occurs by accepting two electrons. We have two electrons here. And we're gonna say here to gain one hydrogen. So here we're gonna gain the hydrogen, the hydrogen will be gained right here. And initially, we're gonna start with two hydrogens. We used one to attach it to our structure to create an A DH, the reduced form. So it to be one left. Now, here are the results of the reduction of N AD plus to N A DH. If we take a look here, the way this works is that both of these H pluses have no electrons whatsoever. And we're gonna say here that two of these electrons would bind to one of these H positives. So two electrons plus the one H positive would give us an H minus gain those two electrons. It's this H minus that is attaching itself to this site right here by attaching it to that site there. That's how it's connected to it and attaching there causes a shifting of our pie box. That's why the structure now looks like this nitrogen here is no longer making four bonds. So it's no longer positively charged. It has a long pair on it though. Again, it's not important to see how these P bonds move around through resonance. What's important to understand here is that we're gonna have this being the site where the H minus attaches. So it's important to know you have N ad plus plus two electrons plus two H plus giving us this structure being able to show the structure and that's a reduced form and then having one H positive left over as a product, right. So that's what we should take away from this particular example reaction.
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example
Nicotinamide Adenine Dinucleotide Example 2
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Which of the following correctly identifies the molecules in the given reaction. So here we have Lactaid interacting with our coenzyme. Our enzyme is lactase dehydrogenase and it's gonna create pyruvate plus N A DH plus H plus. Now, remember N ad positive represents a coenzyme and it's in its oxidized form. If we look at our options, B would be out because N ad positive is not in its reduced form. Next, let's see, we can say that lactase dehydrogenase represents our enzyme. We can say here that this lactate represents our substrate. What kind of substrate? What form is it in here? Well, here this is the oxidized form and over here is its reduced form. So we'd say that N ad positive was reduced right to give us this right now, it's in its oxidized form. If this is in an it's oxidized form, and this is a redox reaction, the substrate would have to be in its reduced form. And we know it's in its reduced form because it's a wage group is later on oxidized to a carbon group. So the substrate here is in its reduced form. So all of those are fine. Let's see, then we're gonna say ND positive is an oxidized coenzyme, oxidized co factors. Just the umbrella term, remember, coal factors can be either organic or inner pyruvate. What does pyruvate represent? Well, here, this is the reduced substrate. So this would have to be the oxidized substrate. So this is good, this is good and this is good. Now it looks like AC or D could be an answer. But what's the best answer? CO factor is just an umbrella term. We gotta be more specific N ad positive represents an organic cofactor. Therefore, it is a coenzyme. So D would be the best answer here because it goes one step further in describing what N ad positive is. Yes, it's oxidized, but more specifically, it is an organic cofactor called a coenzyme. So option D would be our final answer.
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concept
Flavin Adenine Dinucleotide Concept 3
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So F AD is called flavin adenine dinucleotide. We're gonna say the flavin group of F AD is the site of reduction that has two hydrogen atoms added to its nitrogen atoms. Now, here we're gonna say the reduction occurs by adding two electrons to two H pluses in order to form two new covalent bonds. The result of this is the reduction of F AD fa DH two. So here we have our oxidized form of the flare portion of F AD we're reacting to electrons and two H plus is here. And when we reduce this F AD, we get fa DH two, the two hydrogens that we gain one is added here and one is added here. Notice that there is a shifting of our pythons in order to do this. But what's most important is to understand that reduction is happening at this nitrogen and this nitrogen. And we have the transformation of F AD to FA DH two.
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example
Flavin Adenine Dinucleotide Example 3
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Here is this example. It says when F ad oxidizes the substrate, it converts the carbon, single carbon bonds to carbon, double bonded carbon bonds, complete the following reaction, right? So here we have succinate, we have these two sh two carbons in the middle. And then we have these carboxyl groups. At the end, we're basically going to use F AD to go from these single bonded carbon carbon bonds to double bonded carbons. So here now those two carbons are double bonded, they're both still connected to our carboxyl groups. Now, remember carbon must make four bonds. So this carbon here we see making three. So it only have one hydrogen on it. And then same thing with this one. Here, I just chose to put them opposite sides of each other. Doing this would go from succinate to what we call fumarate. Now, it's not important that we know what the name of this molecule is. For this question, I'm just naming it for you. Now, where did those two hydrogens go? Well, we see that succinate lost hydrogens. So it was oxidized, which would mean that F AD had to be reduced. And we know that when we reduce F AD it becomes fa DH two. So these will be our two products formed within this given reaction.
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concept
Coenzyme A Concept 4
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Now, here, we're going to say that coenzyme A is a coenzyme of synthese and it has a high energy file bond. So sh bond it carries in a pedal group to the creb cycle for energy production by oxidation. If we take a look here, this whole structure represents Cohens I may coins, I may is made up of three portions. We have our ad P portion right here which is a denison diphosphate. Then we have here, pantothenic acid, panthothenic acid, another common name for it is vitamin B five. So that would be this portion right here. And then finally, we have our amino ethane thy portion, which is this nitrogen portion with these two ch twos. And then the sh at the end again, it's the sh group that has an high energy bond that hydrogen can be removed from this structure. So just remember coenzyme A is just yet another simple type of coenzyme that exists.
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example
Coenzyme A Example 4
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Now here which of the following statements correctly describes coenzyme A. Here we have to select all that apply first when an acetyl group is released from acetyl coa it produces here just a coa with our thy group. So we're moving this acetyl group here and we replace it with the hydrogen. This is true. Vitamin B is present in the active site of our coenzyme A. No, that's not the active site. It's the amino ethane thy portion, the portion that has the sh group that has the high energy bond. The primary role of K A is to oxidize fatty acids. No, that's not its primary role. Its primary role is to carry an acetyl group to the CRB cycle for it to become oxidized and generate energy. Coenzyme A is composed of pantothenic acid which is vitamin B five amino ethen thiol and AD P. Yes. These are the three major components of our coenzyme A. So here, the only two answers that are true are options A and D
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Problem
Problem
Select the correct statement.
A
When FAD is reduced, it gains 2 hydrogen ions and 2 electrons, forming FADH.
B
NAD+ represents an oxidized form of the coenzyme, and acts as an oxidizing agent.
C
FADH represents an oxidized form of the coenzyme, and acts as a reducing agent.
D
After CoA is oxidized, it forms Acetyl CoA.
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Problem
Problem
Is the following reaction an oxidation or reduction? Which coenzyme would be carrying this out, NAD+ or NADH?
A
oxidation, NAD+
B
oxidation, NADH
C
reduction, NAD+
D
reduction, NADH
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