Glycolysis Summary: Videos & Practice Problems

Glycolysis is a crucial metabolic pathway that converts glucose into pyruvate, yielding energy in the form of ATP and NADH. This process can be divided into two distinct phases: Phase A and Phase B. In Phase A, which encompasses reactions 1 to 5, there is an investment of 2 ATP molecules. This phase is essential for preparing glucose for further breakdown. In contrast, Phase B includes reactions 6 to 10, where the energy-producing events occur, resulting in the generation of 2 NADH and 4 ATP molecules.

Despite producing 4 ATP, the net gain is only 2 ATP because of the initial investment of 2 ATP in Phase A. Overall, glycolysis transforms one molecule of glucose into two molecules of pyruvate, with no carbon dioxide or FADH₂ produced, and a total of 2 NADH generated.

To better understand the reactions involved, it is helpful to remember that glycolysis consists of 10 reactions, with Phase A containing the first five and Phase B the last five. Notably, reactions 1 and 3 are irreversible and require ATP, emphasizing the investment needed in Phase A. A mnemonic to recall this is: "I irresponsibly ate 1 third of a pizza," where "irresponsibly" refers to the irreversible reactions and "1 third" highlights reactions 1 and 3.

In Phase B, reaction 6 is significant as it produces the 2 NADH molecules, while reactions 7 and 10 contribute to the production of ATP. Another mnemonic, "a second 6 pack at the weekend," can help remember that reaction 6 produces 2 NADH, with reaction 7 representing the 7 days of the week, and reaction 10 marking the end of glycolysis. Importantly, reaction 10 is irreversible, meaning it proceeds in one direction only, leading to the formation of the final products, the 2 pyruvates.

In summary, glycolysis is a vital energy-yielding process that efficiently converts glucose into pyruvate while generating ATP and NADH, with specific reactions playing key roles in this metabolic pathway.

Glycolysis is a crucial metabolic pathway that can be divided into two distinct phases: the energy-consuming phase and the energy-producing phase. The energy-consuming phase, known as Phase A, includes reactions 1 to 5, where ATP is utilized rather than produced. In contrast, Phase B encompasses reactions 6 to 10, which are responsible for generating ATP.

To identify which reactions produce ATP, it is essential to focus on Phase B. Specifically, reactions 7 and 10 are the key steps where ATP is synthesized. Reaction 6, while important for the production of NADH, does not contribute to ATP generation. This distinction is critical when analyzing the glycolysis pathway.

To aid in memorization, one can use the mnemonic "6 pack at weekend." Here, "6 pack" refers to reaction 6, which produces NADH, while "weekend" signifies reactions 7 and 10, where ATP is produced. Therefore, the correct answer to the question regarding which glycolysis reactions produce ATP is option C, as it correctly identifies the reactions that contribute to ATP synthesis.

Glycolysis is a crucial metabolic pathway that breaks down glucose to produce energy. The first phase, known as Phase A, involves a series of reactions that can be memorized using the mnemonic: "Glenn's grandpa made a fruity pie, a Fruity Berry Pie Split With Daphne Gilpin." This phrase helps recall the key metabolites involved in the initial steps of glycolysis.

Starting with the first reaction, glucose (represented by "GLENZ") undergoes phosphorylation, consuming ATP to form Glucose 6-Phosphate (Grandpa). This is followed by a reversible reaction that converts Glucose 6-Phosphate into Fructose 6-Phosphate (Fruity Pie), an isomer of the previous metabolite. The third reaction is another phosphorylation, where an inorganic phosphate is added to create Fructose 1,6-bisphosphate (Fruity Berry Pie). At this point, the pathway can diverge, leading to two possible products: Dihydroxyacetone phosphate (Daphne) or Glyceraldehyde-3-Phosphate (Gilpin).

Understanding the enzymes involved in these reactions is essential. The first and third reactions, which are phosphorylation reactions, are catalyzed by kinases. This is due to the transfer of an inorganic phosphate group from ATP to the substrate. The isomerization reaction, which occurs in the second step, is facilitated by isomerases. Notably, there are exceptions in the naming of enzymes: reactions two and three involve enzymes named for their substrate and function, while bond cleavage in reaction four is catalyzed by aldolase.

By memorizing the metabolites and the corresponding enzymes, students can effectively navigate the complexities of Phase A of glycolysis, reinforcing their understanding of this vital biochemical process.

In glycolysis, the conversion of Glucose 6 Phosphate (G6P) to Fructose 6 Phosphate (F6P) is catalyzed by the enzyme phosphoglucoisomerase. Both G6P and F6P are isomers, meaning they share the same molecular formula but differ in their structural arrangement. This transformation is classified as an isomerization reaction, which is facilitated by isomerases, a specific class of enzymes that catalyze the rearrangement of molecular structures.

It is important to distinguish isomerases from other enzyme classes, such as kinases and lyases. Kinases are responsible for transferring phosphate groups between molecules, which is not the case in this reaction since no phosphate transfer occurs. Instead, the reaction involves a simple rearrangement of the molecular structure from glucose to fructose. Therefore, the correct enzyme for this reaction is indeed phosphoglucoisomerase, confirming that option B is the appropriate choice.

In the process of glycolysis, particularly in Phase B, several key reactions transform glyceraldehyde 3-phosphate (G3P) into pyruvate, generating energy in the form of ATP and NADH. This phase can be remembered using a mnemonic: "green peas in a baked potato gratin, then 3 pomegranates and 2 pink grapes to prepare a pie."

The first reaction in Phase B, reaction 6, involves the oxidation of G3P, where NADH is produced. This reaction adds an inorganic phosphate to G3P, resulting in 1,3-bisphosphoglycerate (1,3-BPG). The enzyme responsible for this oxidation is a dehydrogenase, which facilitates the transfer of electrons.

In reaction 7, dephosphorylation occurs, leading to the production of ATP from 1,3-BPG, which is transformed into 3-phosphoglycerate (3-PG). This reaction is catalyzed by a kinase, an enzyme that transfers phosphate groups.

Next, in reaction 8, the inorganic phosphate is relocated from the third carbon to the second carbon, converting 3-PG into 2-phosphoglycerate (2-PG). This is facilitated by a mutase, an enzyme that catalyzes the rearrangement of isomers.

Reaction 9 involves the dehydration of 2-PG to form phosphoenolpyruvate (PEP), a reaction catalyzed by enolase. Finally, in reaction 10, PEP is converted into pyruvate, generating another ATP molecule. This reaction is also catalyzed by a kinase.

Overall, Phase B of glycolysis is characterized by key transformations and energy production, with specific enzymes playing crucial roles in each step. Understanding these reactions and their corresponding enzymes is essential for grasping the metabolic pathways involved in cellular respiration.

In glycolysis, the conversion of 3-phosphoglycerate (3-PG) to 2-phosphoglycerate (2-PG) is catalyzed by the enzyme phosphoglycerate mutase. This reaction involves the relocation of an inorganic phosphate group from the third carbon position in 3-PG to the second carbon position, resulting in the formation of 2-PG. The specific class of enzyme responsible for this type of reaction is known as a mutase, which is a subset of isomerases that specifically moves functional groups within a molecule.

It is important to differentiate this process from other enzymatic reactions. For instance, glyceraldehyde 3-phosphate dehydrogenase is involved in redox reactions, which include oxidation and reduction, but it does not facilitate the movement of phosphate groups within a molecule. Similarly, kinases are enzymes that transfer phosphate groups to molecules, typically increasing the overall number of phosphate groups. However, in this case, no new phosphate is added; rather, the existing phosphate is simply repositioned. Therefore, the correct enzyme for this reaction is indeed phosphoglycerate mutase, confirming that the answer is option D.