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: the energy-consuming phase and the energy-producing phase. In the initial phase, glucose is transformed into Glyceraldehyde 3-Phosphate (G3P), which requires the investment of 2 ATP molecules. This phase encompasses the first five reactions of glycolysis.

In the subsequent phase, which includes reactions 6 to 10, G3P is further processed to produce pyruvate. During this phase, the pathway generates 2 NADH and 4 ATP molecules. Although 4 ATP are produced, the net gain of ATP is 2, as 2 ATP were consumed in the first phase. Additionally, no FADH₂ is produced in glycolysis, and the total yield includes 2 NADH molecules that will be utilized in further metabolic processes.

To remember key aspects of glycolysis, it is helpful to note that reactions 1 and 3 are irreversible and consume ATP, making them critical control points in the pathway. A mnemonic to recall this is "irresponsibly ate 1 third of a pizza," where "irresponsible" signifies irreversible reactions, "8" represents ATP consumption, and "1 third" refers to the first three reactions. Furthermore, reaction 6 is notable for producing 2 NADH, while reactions 7 and 10 each generate 2 ATP. A useful memory aid for this is "second 6 pack at the weekend," where "second" indicates the 2 NADH produced in reaction 6, and "week" symbolizes the 2 ATP produced in reaction 7 and the completion of the pathway in reaction 10.

Finally, it is important to remember that reaction 10 is also irreversible, emphasizing that glycolysis proceeds in a unidirectional manner towards the production of pyruvate. Understanding these key points about glycolysis not only highlights its energy output but also its regulatory mechanisms and significance in cellular metabolism.

To effectively memorize the first five reactions of glycolysis, a helpful mnemonic is "Phil invited Phyllis for baked cookies inside." Each component of this phrase corresponds to a specific reaction type and process involved in glycolysis.

Starting with "Phil," this represents the first reaction, which is phosphorylation. In this step, glucose is converted to glucose 6-phosphate, a process that consumes one molecule of ATP. The second part, "invited," signifies isomerization, where glucose is transformed into fructose, which are isomers of each other.

Next, "Phyllis" again indicates phosphorylation, similar to the first reaction, where another ATP is consumed to convert fructose 6-phosphate into fructose 1,6-bisphosphate. The fourth part, "baked cookies," refers to bond cleavage, specifically the cleavage of the bond between carbons 3 and 4, resulting in the formation of two molecules: glyceraldehyde 3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP). Finally, "inside" highlights the fifth reaction, where isomerization occurs between G3P and DHAP, allowing them to interconvert.

This mnemonic serves as a valuable tool for recalling the types of reactions and the key transformations that occur in the initial stages of glycolysis, emphasizing the importance of phosphorylation, isomerization, and bond cleavage in this metabolic pathway.

To effectively recall the reactions 6 to 10 of glycolysis, we can use a mnemonic device: "Our Pops and Phil tried inventing dry fruity tarts." This phrase helps us remember the key components and transformations occurring in each reaction.

In reaction 6, Glyceraldehyde 3-Phosphate undergoes oxidation and phosphorylation, resulting in the formation of 1,3-bisphosphoglycerate. This step is crucial as it also produces NADH, a key electron carrier in cellular respiration.

Moving to reaction 7, the mnemonic "Phil" signifies a phosphate transfer, where 1,3-bisphosphoglycerate is converted to 3-phosphoglycerate (3-PG). This reaction is significant because it generates ATP, highlighting the energy-yielding aspect of glycolysis.

In reaction 8, the term "venting" refers to isomerization, where 3-phosphoglycerate is transformed into 2-phosphoglycerate (2-PG). This step prepares the substrate for the subsequent dehydration reaction.

Reaction 9, represented by "dry," involves dehydration, converting 2-phosphoglycerate into phosphoenolpyruvate (PEP). This reaction is essential as it sets the stage for the final step of glycolysis.

Finally, in reaction 10, "fruity tarts" indicates a phosphate transfer where phosphoenolpyruvate is converted to pyruvate. This step is critical as it also produces ATP, marking the end of the glycolytic pathway.

Overall, reactions 6 to 10 of glycolysis involve key processes such as oxidation, phosphorylation, isomerization, dehydration, and phosphate transfer, all of which contribute to the efficient conversion of glucose into pyruvate while generating energy in the form of ATP and NADH.