Review of Metabolism - Video Tutorials & Practice Problems
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concept
Review of Metabolism Concept 1
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In this video, we're gonna take a look at metabolism as a whole when it comes to digestion of macro molecules. Now, overall metabolism is seen as catic when we degrade larger molecules and anabolic where we're going to synthesize larger molecules. We're going to say here that these different macro molecules have a metabolic pathways that are interconnected by column metabolites. Now, we've talked about the metabolism in relation to lipids versus carbohydrates. Before now, we're gonna add an additional column when talking about proteins. Now, before we begin, our key here talks about the different pathways. Catic represents our black arrows, anabolic represents our green arrows. And then here are purple are just the transportation across our mitochondrial membrane. You might notice that in this image, we don't have any green arrows. That's because in this part, we're gonna really focus on the interconnections between carbohydrates and proteins because there are metabolites that overlap lap between them heavily lipids, we're gonna ignore because lipids don't overlap with proteins here and because lipids we've talked about in the past, we're gonna gray out a vast majority of what connects to lipids. So if you look here a lot of the green arrows that we could have had were in this are in the sections that are grayed out. Again. You can go back and take a look at our review of metabolites in relation to lipids versus carbohydrates. In earlier sections. Right now, we're mainly concerned with carbohydrates and proteins. So here, if we're looking at our carbohydrates before we do that, remember, we have the exterior of the cell, we have our cell membrane, we have our cytosol, our mitochondrial membranes and then our mitochondrial matrix with carbohydrates, we have the digestion of it to form glucose. And then through glycolysis, we create pyruvate. Pyruvate is where we're gonna start caring about the digestion of carbohydrates pyruvate itself will cross the mitochondrial membrane. So we have this purple arrow. So pyruvate is here. Again, we're not concerning ourselves with the gray portions here. From pyruvate. Pyruvic can do one of two things. Pyruvate can feed into Acey Coe which in turn feeds into the citric acid cycle. Here we have oxalacetate as a chemo tab light. In terms of citric acid cycle, we could also have pyro just going straight into the citric acid cycle. And from there it enters the etc electron transport chain and then oxidated phosphorylation for the creation of A TP. Now, how does this connect to proteins? What with proteins? We can have the digestion of proteins as it crosses the cell membrane and we have our amino acids. These amino acids can do one of two things, they can undergo transamination or they can undergo oxidative deaminate with transamination. They help to make alpha keto acids. This alpha keto acid itself can cross the mitochondrial membrane. And from there, the alpha alpha keto acid has different routes. It can take, it can change into prud itself. Thus linking it to carbohydrates because they share that metabolite in common. Or it can go into acey aceto acetyl coa which then also feeds into acetyl coa. Again, acetyl coa would feed into citric acid cycle and then etc and oxidated phosphorylation to the generation of A TP. Over here, we have oxidated deaminate. Now, here we're skipping some key parts. Remember that the ammonium ion does not directly feed into the urea cycle. We're skipping the CP molecule that is actually prepared. Remember, we're making our carbo oil phosphate group and that is what is going to enter the urea cycle. We're making this chart as simple as possible and not cramming it full of all the intermediates and all the enzymes that are involved. We talked about those in greater details and earlier videos, we're not gonna waste time talking about it here. Remember the urea cycle, we're gonna say that it's composed of reactions. 123 and four, reaction. One happens within the mitochondrial matrix reactions. 23 and four happen outside of the mitochondria in the cytosol. We know that in reaction four, we're gonna create our ornithine molecule. Again, which is regenerated to start the process again. But more importantly, we create uria as our waste material in the cytosol that's eventually excreted out in our urine. Now, what also connects proteins and carbohydrates has to do the connection between the urea cycle and the citric acid cycle. The metabolites that they share in common are your aspartate amino acid here. And then we have fate here. Now here, remember when it comes to reaction two of the urea cycle we have are aspartate molecule coming in from the outside. Well, that's coming from the citric acid cycle. And technically, the step two happens outside mitochondria. So remember it's reaction one that's happening inside the mitochondrial matrix when it comes to the urea cycle and reactions 23 and four are happening in the cytosol. We're gonna say next that fumarate. Remember, fumarate is created in reaction three of the rhea cycle which is the cleavage um step. So that's created by urea cycle that can feed into the citric acid cycle. So these two metabolites are what connects the urea cycle of proteins to the citric acid cycle that we have. Here. Again, the citric acid cycle can also connect to proteins through a longer pathway, but it also can come from carbohydrates itself. So just keep that in mind, we have these different types of macro molecules, lipids, carbohydrates and proteins. They are connected to one another because they do share certain key metabolites uh that they have in common with one another, right. So just keep a big idea, big picture when it comes to how these macro molecules are digested, the different types of structures that are produced, how they traverse across membranes and they undergo canna bolic or anabolic processes in order to generate um other molecules or to create a TP.
2
example
Review of Metabolism Example 1
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Here it says which of the following statements is true. Lipid and protein metabolism provide the only cat bolic pathways to acetyl coa formation. That statement is false. We know that carbohydrates, when we digest them, they can also provide another pathway, another catic pathway to acetyl coa formation. So this statement is false here. A transaminase is the class of enzyme that catalyzes transamination reactions. The name gives it away. This is what this enzyme is intended to do. Remember in a transamination reaction, we are exchanging in a reversible reaction. The amino group of an amino acid with the keto group of an alpha keto aid. So this statement is true when glycogen stores are at max levels, fatty acids are degraded for energy. Now, if you have a surplus of carbohydrates or sugars, we break that down first to gain energy. Alanine and an alpha ketoglutarate reacting to form pyruvate and G glutamate represents an oxidative deaminate. Remember in an oxidative deaminate, we have glutamate undergoing oxidation to create alpha ketoglutarate. We use N ad positive in order to do this, this is saying the opposite. So here it's saying that we're using an alpha kag Gluta to make uh glutamate when it should be reversed. That is what oxidative deaminate is. So here, the only statement that's true wouldn't be, have, would have to be option B.
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Problem
Problem
Which of the following statements is incorrect?
A
Ammonia molecules are converted to carbamoyl phosphate before entering the Urea Cycle.
B
The production of urea requires the reaction between water and a glutamate molecule.
C
The Urea Cycle excretes urea as a waste material by using NH4+ and aspartate as the sources of nitrogen.
D
It requires 4 total ATP molecules to produce one urea molecule.
4
Problem
Problem
In the synthetic pathway of serine, 3-phosphoglycerate must first be converted into 3-phosphohydroxypyruvate.
Identify the type of reaction represented by this conversion.
A
Condensation
B
Reduction
C
Transamination
D
Oxidation
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Problem
Problem
Which of the following statements is incorrect?
A
The products of a transamination reaction are a new amino acid and an α-keto acid.
B
The ammonium ion produced in the liver must immediately be excreted as urea because of its toxicity.
C
Glutamate converting to α-ketoglutarate and an ammonium ion represent an oxidative deamination reaction.
D
Ammonia molecules directly enter the Urea Cycle to serve as the only nitrogen source.
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Problem
Problem
Determine whether each of the following is involved in Glycolysis (A), β-Oxidation (B), Transamination/ Oxidative Deamination (C), or Urea Cycle (D).
I. _____ Using alanine transaminase on alanine and α-ketoglutarate to form pyruvate and glutamate.
II. _____ Phosphofructokinase or fructose-1,6-bisphosphate.
III. _____ The continuous regeneration of Ornithine.
IV. _____ Cleavage of a 2-carbon acetyl group.
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