Glycolysis Summary - Online Tutor, Practice Problems & Exam Prep

Glycolysis is a metabolic pathway that converts glucose into pyruvate, yielding 2 NADH and 2 net ATP after an initial investment of 2 ATP. It consists of two phases: Phase A (reactions 1-5) involves phosphorylation and isomerization, while Phase B (reactions 6-10) focuses on energy production through oxidation and substrate-level phosphorylation. Key enzymes include kinases for phosphorylation and dehydrogenases for oxidation. The overall reaction does not produce carbon dioxide or FADH₂, emphasizing its role in anaerobic metabolism.

Glycolysis Summary Concept 1

Hello everyone. In this video, we're going to take a look at glycolysis energy output. Here, we're going to say that glycolysis oxidizes glucose to pyruvate and produces 2 NADH and 4 ATP molecules. Now remember, glycolysis is made up of 2 phases, Phase A and Phase B. Phase A consists of reactions 1 to 5, and we're going to say that it requires an investment of 2 ATP. Phase B includes reactions 6 to 10, this is the energy producing phase of glycolysis. In it, we make 2 NADH and 4 ATP. Now here, our net creation of ATP is only 2, because we had to invest 2 to get 4 out. So in essence, we've only really made 2 brand new ATP. And if we take a look here, we're gonna say that our overall set of glycolysis is our starting molecule, which is glucose. In this process, we're going to wind up making 0 carbon dioxides. We're going to make 2 net ATP. We're going to make 0 FADH₂, we're going to make 2 NADH in order to make 2 Pyruvates at the end.

Now, here we're going to have some memory tools to help us remember how the phases are set up. Now, here we're going to say we have 10 reactions that are equally divided into 2 phases. Remember, phase A is reactions 1 to 5, phase B is reactions 6 to 10. Here, we're going to say that reactions 1 and 3 are irreversible and they're the ones that use ATP. Remember, phase A requires an investment of 2 ATP. Next, we're going to say our memory tool 1 to help us remember some of this is, "I irresponsibly ate one third of a pizza". Glycolysis is a cyclic type of pathway, so like a pizza cyclic. "Irresponsibly," irreversible, "ate pizza," so we're talking about ATP, and "one third," reactions 1 and 3.

Next, we're going to say reaction 6 is what produces our 2 NADH energetic molecules, reaction 7 and 10 produce 2 ATP. Memory tool 2 says that our second "six-pack" at the weekend. "2nd six-pack," we have 2 NADH that are made in reaction 6. A week is 7 days long, reaction 7. The end of glycolysis is reaction 10, so "end" is 10.

Finally, memory tool 3 tells us that row 10 is one way. When it comes to reaction 10, it only goes one way, it's not a reversible reaction. So "row 10," reaction 10 goes only one way, forward, to make our 2 pyruvates as our final molecules. So keep this in mind when we're taking an overview of the energy output of glycolysis and some key factors to remember when it comes to specific reactions of glycolysis.

Glycolysis Summary Example 1

This example asks which of the following glycolysis reactions produce ATP? Recall that glycolysis is divided into two phases. Phase A, which is the energy-consuming phase, and Phase B, which is the energy-producing phase in terms of ATP. Therefore, Phase B contains reactions 6 to 10. It's in these reactions where ATP could be produced. Because of this, that means option B is out because reactions 1 and 3 are part of Phase A, where ATP is not being produced, it's being consumed. Also, option D is out because again reaction 3 is part of Phase A. This leaves us with either option A or option C. Now remember, our memory tool 2, we're going to say "a 6 pack at weekend." This phrase helps us to recall that energetic molecules are being created. We say "6 pack," reaction 6 means we're making NADHs, and "weekend," reactions 7 and 10, with "7 days in a week" and "end" indicating reaction 10, the last reaction of glycolysis. Reactions 7 and 10 are where ATP will be produced. Hence, the answer is option C. Option A doesn't work because although reaction 6 is where we create NADH, and reaction 7 does produce ATP, reaction 6 does not produce ATP.

How many NADH molecules are produced in phase B of glycolysis?

• A. 2
• B. 3
• C. 1
• D. 4

Glycolysis Summary Concept 2

Hey, everyone. So in this video, we're going to talk about tools we can use to help us remember Phase A of Glycolysis. Now, here we're going to say glycolysis reactions can be remembered by memorizing the metabolite names. Now, memory tool 4 is, Glenn's grandpa made a fruity pie, a Fruity Berry Pie Split With Daphne Gilpin. Alright. So here, what does it stand for? We're gonna say here, that GLENZ is glucose. We know that reaction 1 is a phosphorylation reaction in which we consume ATP in order to create Glucose 6 Phosphate, which represents Grandpa. We're gonna have reaction 2 which is reversible, and it made Fructose 6 Phosphate, so this represents Fructose 6 Phosphate, an isomer of Glucose 6 Phosphate. Now, going to reaction 3 is yet again another phosphorylation reaction. Here, we're going to add an inorganic phosphate again to create fructose 1,6-bisphosphate or a fruity berry pie. Here it's split because we can go one of two ways. We can go this way or that way. We can split to make dihydroxyacetone phosphate or Daphne, or we can make Glyceraldehyde-3-Phosphate which is Gilpin. Here we're going to say that the name of the enzyme can be predicted by knowing the substrate and the type of reaction. Hint 1: Phosphorylation reactions 1 and 3 are catalyzed by kinases. Because remember, we have the transferring of an inorganic phosphate group from ATP to our specific molecule. Hint 2: isomerization reactions 2, 5 are catalyzed by isomerases. Now, exception 1: reactions 2, 3 are enzymes named as phospho substrate and then function. So here we're gonna say, exception 2, bond cleavage which is catalyzed by aldolase. So these are the two exceptions that we have. But here just remember the phrase in order for us to remember the metabolites involved, and then to remember what kind of enzymes do what type of functions from reactions 1 to 5, or phase A of glycolysis.

Glycolysis Summary Example 2

This example question asks, "Which enzyme in glycolysis catalyzes the conversion of Glucose 6-phosphate, otherwise known as G6P, to Fructose 6-phosphate, known as F6P?" First of all, Glucose 6-phosphate and Fructose 6-phosphate are isomers of one another. They have the same molecular formula but just different connections. And because they're isomers of each other, this is an isomerization reaction. The class of enzymes we would use would have to be an isomerase. If we look at our options, the answer would have to be option B. We'd use phosphoglucoisomerase to go from G6P to F6P. Options A and C deal with kinases. Remember, kinases are the class of enzymes that deal with phosphate transfers. Here that's not what's going on. We are basically going from glucose to fructose, so we are doing an isomerization. The molecule is changing its connections to go from one form to another form. We're not transferring a phosphate group from one molecule to a new specified molecule. So, we wouldn't be using a kinase. And, we haven't talked about all the laces yet, so this wouldn't work as an option either. So, here the answer would have to be option B.

Write the names of the substrate and the product of reaction 3 of glycolysis.

• A. Glucose and glucose-6-phosphate
• B. Fructose-6-phosphate and fructose-1-phosphate
• C. Fructose-1,6-bisphophate and glyceraldehyde-3-phosphate
• D. Fructose-6-phosphate and fructose-1,6-bisphosphate

Glycolysis Summary Concept 3

Everyone, in this video, we're going to go over different memory tools and hints to help us remember the parts of Phase B of glycolysis. Now, memory tool 5 is, green peas in a baked potato gratin, then 3 pomegranates and 2 pink grapes to prepare a pie. Right. So, here we start out with Glyceraldehyde 3-Phosphate, which we created in reaction 5 or phase A of glycolysis. Now we're going to start out with reaction 6 for phase B of glycolysis. Here is where we make our NADH as our energetic molecule. This allows us to add an inorganic phosphate to G3P, transforming it into 1,3-bisphosphoglycerate. So green peas in a baked potato gratin.

We're going to have reaction 7, which is where we create ATP. This is where we're going to have dephosphorylation occur, where we lose one of our inorganic phosphates. So 3-phosphoglycerate is 3 Pomegranates. Reaction 8, is where we move the inorganic phosphate from position 3 to position 2, transforming it into 2-phosphoglycerate. So, 3 pomegranates becomes 2 pink grapes. Then we're going to have reaction 9 where we're going to lose water to create PEP which is phosphoenopyruvate. PEP is connected to prepare. Then finally, we're going to have reaction 10 where we make pyruvate and also another ATP molecule. Here, pyruvate will represent our pie.

Now, here we're going to say the name of the enzyme can be predicted by knowing the substrate and the type of reaction. Hint 3, an oxidation reaction occurs in reaction 6. And remember, we talked about oxidation reactions before, our class of enzymes that we tend to use are the dehydrogenases. So it's catalyzed by dehydrogenase. Hint 4, we have dephosphorylation in reaction 7 and 10, which help us to make ATP, they are catalyzed by our kinases because they involve a phosphate transfer.

And then we have exceptions. Here, our change in the inorganic phosphate location of reaction 8 is catalyzed by a mutase. Here we're going from G3P to 2PG, we're creating isomers. So this class of isomers specifically is a mutase. Here we're going to say that we have reaction 4, which is a dehydration reaction. It's catalyzed by an enolase. So this would be the enzyme that we use.

So these are the ways that we can remember the different types of metabolites found in phase B of glycolysis and the enzymes corresponding with each of the reactions. So keep this in mind when we're asked questions dealing with Phase B of glycolysis.

Glycolysis Summary Example 3

In this example, it says, "Which enzyme in glycolysis catalyzes the conversion of 3PG to 2PG?" Now, the difference between these two molecules is that we have our inorganic phosphate moving from position 3 in 3PG to position 2 to create 2PG. The class of enzyme that we'd use specifically in order to move a functional group on a structure would have to be a mutase. So, here, if we take a look, that would mean that my answer would have to be phosphoglycerate mutase. This is the enzyme we'd have to use in order to do this.

Here, Glyceraldehyde 3-Phosphate Dehydrogenase. Dehydrogenases deal with redox reactions, oxidations, or reductions. That's not what's occurring here. We are moving the inorganic phosphate from one portion of the molecule to another portion. In essence, making a different type of isomer. But, the isomer specifically, the subset of it would have to be a mutase. So here, this would not work. This isomerase? No. Specifically, we're moving a functional group from one portion to another portion, that subset would have to be a mutase.

Now, a kinase, remember a kinase deals with phosphate transfers. That's not what's occurring here. A phosphate transfer would mean that we're adding an additional phosphate to 3PG to create something new. We are not adding a new phosphate group, increasing the number overall. We're just moving a functional group, the inorganic phosphate, to another part of the molecule. So it wouldn't be a kinase. So again, the answer here would have to be option D. It's a mutase.

What is the name of the product of glycolysis reaction 9?

• A. 3-Phosphoglycerate
• B. Phosphoenolpyruvate
• C. 2-Phosphoglycerate
• D. Pyruvate

Which two steps of phase A of glycolysis utilize ATP as a coenzyme?

• A. Reactions 2 and 3
• B. Reactions 1 and 3
• C. Reactions 4 and 5
• D. Reactions 2 and 4

What is the name of the product when 1,3-bisphosphoglycerate loses a phosphate group?

• A. Phosphoenolpyruvate
• B. 1-Phosphoglycerate
• C. 2-Phosphoglycerate
• D. 3-Phosphoglycerate

Which one of the following statements is incorrect about phase A of glycolysis?

• A. Phosphorylation in reactions 1 and 3 requires ATP as the coenzyme.
• B. Energy from ATP hydrolysis is required to cleave the C–C bond in reaction 4.
• C. Except for the energy-consuming reactions 1 and 3, the other three reactions are reversible.
• D. Isomerization of DHAP into G3P is reversible.

For each of the following reactions described below, identify a corresponding step of glycolysis.

a) ____ Phosphorylation of glucose to produce glucose-6-phosphate.

b) ____ Formation of a hexose phosphate from a hexose.

c) ____ An oxidation reaction is catalyzed by glyceraldehyde-3-phosphate dehydrogenase.

d) ____ Phosphorylation of fructose-6-phosphate to produce fructose-1,6-bisphosphate.

Each of the fungal ring reactions described below, identify a corresponding step of glycolysis. So here it says, "Phosphorylation of glucose to produce Glucose 6-Phosphate." Well, this is what kicks off glycolysis; this is reaction 1 of glycolysis. This reaction will require ATP serving as a coenzyme in order to phosphorylate the glucose. Formation of a Hexose Phosphate from a hexose. Well, glucose is a hexose ring, a sugar, and we are utilizing ATP as a coenzyme in order to add a phosphate group to it. So, glucose which is hexose is transformed into glucose 6-phosphate which is a hexose phosphate. So, this is also reaction 1. An oxidation reaction is catalyzed by Glyceraldehyde-three Phosphate dehydrogenase. This happens in step 6 of glycolysis, so Phase B of glycolysis. This is what's going to help us to change G 3P, which is Glyceraldehyde 3-Phosphate into 1,3-bisphosphoglycerate. So, here we're going to say again this is reaction 6. Phosphorylation of Fructose 6-Phosphate to produce Fructose 1,6-Bisphosphate. This is also a phosphorylation step. Remember our 2 reactions that deal with phosphorylation in glycolysis are reactions 1 and 3. So, this has to be reaction 3. So this outlines the steps which correspond to each of the following statements in regards to glycolysis.

What compound is converted to phosphoenolpyruvate in glycolysis?

• A. Pyruvate
• B. 1,3-Bisphosphoglycerate
• C. 2-Phosphoglycerate
• D. Glucose-6-phosphate

What is the name of the product of the glycolysis reaction which produces NADH?

• A. Glyceraldehyde-3-phosphate
• B. 3-Phosphoglycerate
• C. 2-Phosphoglycerate
• D. 1,3-Bisphosphoglycerate

Which reaction of glycolysis produces a hexose bisphosphate from a hexose phosphate?

• A. 1
• B. 6
• C. 3
• D. 2

Which reactions of the glycolysis pathway involve a phosphate transfer?

• A. Reactions 1, 3, 7, and 10
• B. Reactions 1, 6, 8, and 10
• C. Reactions 1, 3, 7, and 9
• D. Reactions 2, 3, 6, and 8

Which reaction of the glycolysis pathway is catalyzed by the enzyme pyruvate kinase?

• A. Reaction 9
• B. Reaction 10
• C. Reaction 6
• D. Reaction 7

Here’s what students ask on this topic:

What is the net ATP gain from glycolysis?

The net ATP gain from glycolysis is 2 ATP molecules. Although glycolysis produces a total of 4 ATP molecules, it requires an initial investment of 2 ATP molecules during Phase A (reactions 1-5). Therefore, the net gain is calculated as 4 ATP produced minus 2 ATP invested, resulting in a net gain of 2 ATP.

What are the two phases of glycolysis and their main functions?

Glycolysis consists of two phases: Phase A and Phase B. Phase A (reactions 1-5) involves phosphorylation and isomerization, requiring an investment of 2 ATP molecules. Phase B (reactions 6-10) focuses on energy production through oxidation and substrate-level phosphorylation, yielding 2 NADH and 4 ATP molecules. The net result is 2 ATP and 2 NADH, as 2 ATP were initially invested in Phase A.

Which enzymes are involved in the phosphorylation reactions of glycolysis?

The enzymes involved in the phosphorylation reactions of glycolysis are kinases. Specifically, hexokinase catalyzes the phosphorylation of glucose to glucose-6-phosphate in reaction 1, and phosphofructokinase catalyzes the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate in reaction 3. Both reactions require ATP investment.

How is NADH produced during glycolysis?

NADH is produced during glycolysis in reaction 6 of Phase B. In this reaction, glyceraldehyde-3-phosphate (G3P) is oxidized by the enzyme glyceraldehyde-3-phosphate dehydrogenase, resulting in the formation of 1,3-bisphosphoglycerate and the reduction of NAD⁺ to NADH. This reaction is crucial for the energy yield of glycolysis.

What is the final product of glycolysis?

The final product of glycolysis is pyruvate. Each molecule of glucose is converted into two molecules of pyruvate through a series of ten enzymatic reactions. Pyruvate can then enter the mitochondria for further oxidation in the citric acid cycle under aerobic conditions or be converted to lactate under anaerobic conditions.