Intro to Gluconeogenesis - Online Tutor, Practice Problems & Exam Prep

Gluconeogenesis is the synthesis of glucose from non-carbohydrate sources, primarily occurring in the liver during low carbohydrate intake or fasting. This anabolic process converts lactate, amino acids, and glycerol into glucose, crucial for brain energy. It contrasts with glycolysis, which breaks down glucose into pyruvate. Key irreversible steps in glycolysis are bypassed in gluconeogenesis using different enzymes, activated when blood glucose levels drop. Understanding these metabolic pathways is essential for grasping energy regulation in the body.

Intro to Gluconeogenesis Concept 1

Now, there are 2 ways that we could get glucose. One way is pretty obvious. We eat carbohydrates. A second way to make glucose is to synthesize it. And this is where gluconeogenesis comes into play. Now, gluconeogenesis is when your blood glucose is low, and we're gonna say, glucose is synthesized from non-carbohydrate sources for energy. Now here we're going to say this is most active when the diet is low in carbohydrates or in times of fasting. Now, this is incredibly important that we are able to synthesize glucose during these periods because glucose serves as the major energy source for our brain. Now, here, gluconeogenesis is an anabolic process that occurs mainly in the liver. And recall, anabolism involves reactions that use energy to build larger molecules from smaller molecules. If we take a look here at the liver, our non-carbohydrate sources we have as lactate and the amino acids. They can be converted to pyruvate, which in turn can be changed into DHAP (dihydroxyacetone phosphate) . From there, it can be transformed into the creation of glucose. We can also say that we have Glycerol as yet another way of converting it into DHAP and then towards making glucose. So, just remember, when it comes to glucose, there are 2 ways that we can get it. We can eat carbohydrates or we can synthesize them. In this case, synthesis means that we have to utilize gluconeogenesis.

Intro to Gluconeogenesis Concept 2

In this video, we'll talk about the difference between gluconeogenesis and glycolysis. Now, here we're going to say that gluconeogenesis can be viewed as the reverse of glycolysis with some exceptions. So remember, with glycolysis, we're starting out with glucose, we go through 10 reactions to get to 2 pyruvate molecules. In gluconeogenesis, we're going the other way. We're trying to create pyruvate through non-carbohydrate sources, and from pyruvate, we're trying to get back to glucose. Now here, recall that when it comes to glycolysis, we say reactions 1, 3, and 10 are irreversible. Now, gluconeogenesis bypasses these irreversible reactions by using different enzymes. These enzymes are upregulated whenever your blood glucose levels are low. So that's how we're able to bypass these irreversible processes that we've seen in glycolysis.

Intro to Gluconeogenesis Example 1

In this example question, it says, "Identify all the statements that are not true about gluconeogenesis." So, option A states, "Gluconeogenesis is the exact reverse of the glycolysis pathway." This statement is not true. It is not the exact reverse; there are some exceptions that occur. That's why this is not true. It is not an exact opposite or reverse, as there are some exceptions.

Gluconeogenesis primarily occurs in the liver cells. That is true. It is most active in times of fasting or starvation. This is also true. When your blood glucose levels are low, this process will kickstart the synthesis of glucose through gluconeogenesis.

Certain non-carbohydrates have to be converted to pyruvate before entering the gluconeogenesis pathway. Yes, certain non-carbohydrates, such as lactate and amino acids, must be converted into pyruvate, from pyruvate to dihydroxyacetone phosphate (DHAP) before they can eventually become glucose. So this last statement is true.

Out of our four statements, only option A is an incorrect or false statement. Here, gluconeogenesis is not the exact reverse of the glycolysis pathway, as it is the reverse with some exceptions that exist.