Gluconeogenesis Flashcards
What is gluconeogenesis and when does it occur?
The metabolic pathway in which glucose is synthesized from non-carb sources of pyruvate (In liver and kidneys). It’s the reverse of glycolysis.
This occurs when blood glucose is low.
Why does gluconeogenesis occur in the cytosol where all of the enzymes needed for the gluconeogenesis reactions are located?
Each of the steps of gluconeogenesis require a specific enzyme to facilitate the chemical reaction. The enzymes needed for gluconeogenesis are located in the cytosol of the cell, so that is where gluconeogenesis reaction occurs.
A metabolic reaction always occurs where the enzymes needed for the reaction are located.
What is the starting input (reactant) for gluconeogenesis and what is the final output (end products)?
Pyruvate from a non-carbohydrate source is the input required for the gluconeogenesis to begin, whereas the output is glucose.
Where does the input required for gluconeogenesis come from? (Three sources)
Pyruvate from a non-carbohydrate source is needed to begin gluconeogenesis.
Comes from:
AA metabolism of alanine and aspartate
the conversion of oxaloacetate to pyruvate
the conversion of lactate into pyruvate via the Cori cycle.
What is the final output of gluconeogenesis used for? For what purpose?
The glucose produced in gluconeogenesis is moved from the cell into the blood and can be trafficked to where it is required.
eg: glucose-dependent organs such as the brain and the kidney.
Can then undergo glycolysis and the common metabolic pathway are used to generate a lot of ATP from the glucose.
Why is it necessary for us to perform the gluconeogenesis? Why is it important?
Gluconeogenesis is required in times where carbohydrate intake is restricted.
The body needs to maintain blood glucose between 4-7.8 mmol/L.
Having a constant supply of glucose in the blood allows it to be taken to cells and organs that required glucose to derive ATP (cellular energy).
Gluconeogenesis is under the control of enzymatic regulation at several steps throughout the reaction. Why is enzymatic regulation of the gluconeogenesis required?
Allows gluconeogenesis to be performed when more glucose is required to either increase the blood glucose and/or generate ATP.
OR when glucose is abundant after an individual has ingested a carbohydrate-rich meal, no more glucose needs to be made so enzymes regulation is used to stop gluconeogenesis.
Positive and negative regulators bind to the enzyme’s regulatory binding site to increase and decrease the activity of the enzyme, respectively.
Why do some of the reactions of gluconeogenesis use the exact same enzymes as those used in glycolysis?
Gluconeogenesis and glycolysis are essentially metabolic reactions that are the reverse of one another.
Gluconeogenesis uses a non-carbohydrate source of pyruvate as the input to produce glucose (output), whereas glycolysis uses glucose to produce pyruvate.
All steps are reversible except 1, 3, 10
Which steps of glycolysis can not be reversed by using the identical enzymes in gluconeogenesis?
Steps 1, 3 and 10.
How does gluconeogenesis bypass the non-reversible steps of glycolysis?
Gluconeogenesis uses different enzymes to bypass the irreversible reactions of glycolysis.
Steps 1 and 3 of glycolysis involve ADDING a Pi unit to the glycolysis compound. (Gluconeogenesis uses a different enzyme to REMOVE a Pi unit.
Step 10 of glycolysis requires TWO gluconeogenesis reactions to bypass. In the first reaction, pyruvate is converted to oxaloacetate and then the oxaloacetate is converted to phosphoenolpyruvate. The energy barrier is too large to convert pyruvate back to phosphoenolpyruvate in a single step.
What types of metabolic reactions does insulin activate? Give examples.
Options: Glycolysis, gluconeogenesis, glycogenesis, glycogenolysis.
Glycolysis to derive energy
Glycogenesis = storage as glycogen.
What types of metabolic reactions does glucagon activate? Give examples.
Options: Glycolysis, gluconeogenesis, glycogenesis, glycogenolysis.
Gluconeogenesis = makes glucose from a
non-carbohydrate source of pyruvate.
Glycogenolysis = breaks down glycogen
into glucose.
