Glycolysis Flashcards
What is Glycolysis
The catabolic pathway in which glucose (C6) is broken down into 2 molecules of pyruvate (C3). Also producing 2 ATP and 2 NADH.
Why does glycolysis occur in the cytosol where all of the enzymes needed for the glycolysis reactions are located?
Each of the steps of glycolysis requires a specific enzyme to facilitate the chemical reaction. The enzymes needed for glycolysis are located in the cytosol, so that is where the glycolysis reaction occurs. A metabolic reaction always occurs where the enzymes needed for the reaction are located.
What is the starting input (reactant) for glycolysis and what is the final output (end products)?
Input: glucose is required for glycolysis to begin.
Output:
Two pyruvate compounds
Two ATP
Two NADH
Where does the input required for glycolysis come from?
From the digestion of complex carbohydrates.
Once glucose enters the blood after digestion, the release of insulin promotes the movement of glucose into the cell.
Once inside the cell, glucose can be used in glycolysis.
What is the final output of glycolysis used for under anaerobic and aerobic conditions? For what purpose?
Aerobic (in the presence of oxygen) PYRUVATE is converted to acetyl CoA. (The central metabolite that is mainly used in the CAC).
The CAC connects to the electron transport chain/oxidative phosphorylation where a lot of ATP is made.
Anaerobic (absence of oxygen), PYRUVATE is converted to lactate which allows more ATP to be made via glycolysis.
Why is it necessary for us to perform the glycolysis reaction? Why is it important?
Glycolysis is necessary to create pyruvate, which is converted to Acetyl CoA in order to continue the bioenergetic pathway, which creates a lot of ATP.
Glycolysis is under the control of enzymatic regulation at steps 1, 3 and 10. Why is enzymatic regulation of glycolysis required?
Enzymatic control allows glycolysis to be performed only when ATP is required.
When there is already a lot of ATP glycolysis will stop and enzymes are needed to facilitate each of the glycolysis reactions.
The enzymes needed in steps 1, 3 and 10 are ALLOSTERIC enzymes with REGULATORY binding sites.
(when ATP is not required, a negative regulator binds to one of the allosteric enzymes to prevent one of the glycolysis reactions from occurring, which stops glycolysis and ATP production.
In the preparation phase of glycolysis, steps 1 and 3 of glycolysis are phosphorylation reactions which each require 1 ATP to be performed (two ATP required in total).
Do the products of steps 1 and 3 have more or less phosphate units attached than the initial reactants? How does ATP assist these reactions?
The products of steps 1 and 3 have ONE MORE phosphate unit attached than the reactant compounds.
ATP is converted to ADP via the breakage of a phosphoanhydride bond which releases energy and a phosphate unit.
The energy released from ATP assists the conversion of the reactant to the product and the phosphate unit lost from ATP attaches to the product.
Steps 6 of glycolysis is another phosphorylation reaction but in this step NAD+ is also required. In the course of the reaction NAD+ is converted to NADH. Is NAD+ oxidised or reduced in the redox reaction that converts it to NADH?
In step 6 of glycolysis, NAD+ is reduced to NADH, which allows the reactant to be oxidised where the reactant loses a hydrogen atom.
An additional phosphate unit is attached to the product in the position where the hydrogen atom had been lost (due to oxidation).
In the pay-off phase of glycolysis, steps 7 and 10 of glycolysis are substrate level phosphorylation steps. ATP is a product of each of these reactions (each reaction occurs twice for a total of 4 ATP).
Where does the additional phosphate come from to regenerate ATP (from ADP) in these steps?
The phosphate unit that attaches to ADP in order to regenerate ATP comes off the reactant of the glycolysis reaction.
As a result, the product of the reaction has one less phosphate unit than the initial reactant did.
Is Glycolysis activated or deactivated by the following:
Insulin
Glucagon
Glycolysis is activated by Insulin
Deactivated by Glucagon
What happens in step 1 of Glycolysis?
Glucose»_space;> Glucose 6-phosphate
via phosphorylation
What happens in step 2 of Glycolysis?
Glucose 6-phosphate»_space;> Fructose 6-phosphate
via isomerisation
What happens in step 3 of Glycolysis
Fructose 6-phosphate»_space;> Fructose 1,6-bisphosphate
via phosphorylation
What happens in step 4 of Glycolysis?
form dihydroxyacetone + glyceraldehyde 3-phosphate
via cleavage of C6 to 2 C3s
