L5 Glycolysis Flashcards
What are the three main metabolic processes involved in complete oxidation of glucose?
(1) Glycolysis
(2) Citric acid cycle
(3) Electron transport and oxidative phosphorylation
Are there any ATP consuming steps in glycolysis?
Yes
What is special about Hexokinase IV?
It is the only hexokinases that is glucose-specific, and it is found only in liver cells
Glycolysis supplies carbon skeleton for other biomolecules, true or false?
True
Pyruvate is converted to which metabolite for further catabolism during aerobic condition?
Acetyl Co-A
And CO2 is released in this process
Which stage of glycolysis consumes ATP, and which produces ATP?
In hexose stage, 2 ATP are consumed per glucose
In triose stage, 4 ATP are generated per glucose
Pyruvate is converted to which metabolite for further catabolism during anaerobic condition?
lactate or ethanol
Hexose stage of glycolysis is also known as what phase?
Preparatory phase
Triose stage of glycolysis is also known as what phase?
Payoff phase
In the three irreversible steps, which metabolite is transformed to which respectily?
(1) Step 1: Glucose is phosphorylated to Glucose-6-phosphate
(Adding the first phophate group)
(2) Step 3: Fructose 6-phosphate is phosphorylated to Fructose 1,6-bisphosphate
(Adding the second phophate group)
(3) Step 10: Phosphoenolpyruvate turns to Pyruvate
(Getting the last phophate down)
What is the enzyme related to Glucose being phosphorylated to Glucose-6-phosphate?
Hexokinase
What is the enzyme related to Fructose 6-phosphate being phosphorylated to Fructose 1,6-bisphosphate?
Phosphofructokinase-1
(PFK-1)
What is the function of Glucose 6-phosphate isomerase?
It converts Glucose-6-P to Fructose-6-P in step 2 of glycolysis
What is the enzyme related to Phosphoenolpyruvate (PEP) turning to Pyruvate?
Pyruvate kinase
Which is the first committed step in glycolysis?
Step 3: phosphorylation of Fructose 6-phosphate
Being the committed step means once F6P is turned to F1,6-bisP, it is for Glycolysis only and will not enter other pathways
For example, before this step, G6P can still enter Entern-Doudoroff Pathway
What is the function of Aldolase?
It cleaves the C3-C4 bond in F 1,6-bisP and produce DHAP and G3P in step 4 of glycolysis
What is the function of Triose phosphate isomerase?
It isomerizes DHAP to G3P in step 5
What type of enzyme is Triose phosphate isomerase?
It is a general acid-base catalysis
What is the function of G3P dehydrogenase?
It turns G3P into 1,3-Bisphosphoglycerate in step 6, using NAD+ and an inorganic Pi as another substrate
Which step uses NAD+ as oxidizing agent?
In step 6 when turning G3P to 1,3-Bisphosphoglycerate
In which step an inorganic phosphate is used for phosphorylation?
In step 6, when phosphorylating G3P to 1,3-BPG
What is the function of Phosphoglycerate kinase?
Use one phosphate group in 1,3-Bisphosphoglycerate to generate ATP in step 7
What does substrate level phosphorylation mean?
Phosphorylation of ADP through hydrolysis of a phosphorylated substrate
In step 7, stabilization of the product 3-phosphoglycerate if achieved by what?
Resonance hybrid formation
In which step the arsenate poisoning will affect?
Step 6 when turning G3P to 1,3-Bisphosphoglycerate with the help of NAD+, because that step uses an inorganic Pi
What is the function of Phosphoglycerate mutase?
It catalyzes intramolecular phosphoryl group transfer, turning 3-phosphoglycerate to 2-phosphoglycerate
What is the function of Enolase?
It turns 2-Phosphoglycerate to Phosphoenolpyruvate (PEP)
What is the function of Pyruvate kinase?
It uses the phosphate group in PEP to generate ATP
What process stabilizes the product pyruvate?
Tautomerization
After which step, glycolysis finally turns a profit?
After the last step of PEP hydrolysis
The process of turning pyruvate to either ethanol or lactate is both reduction or oxidation?
Reduction
The anaerobic metabolism of pyruvate generates how many ATP per pyruvate?
2 ATP per pyruvate
The anaerobic metabolism of pyruvate regenerate what metabolite for glycolysis?
NAD+
Which sugar’s entrance into glycolysis needs the UDP-glucose for sugar transfer?
Entry of galactose into glycolysis
Regulation of glycolysis is completed through which two process?
(1) Regulation of hexose transporters
(1) Regulation at 3 irreversible steps of glycolysis
What can regulate Hexokinase one two and three?
Glucose 6-phosphate(the product), it inhibits Hexokinase one two and three
What can regulate Phosphofructokinase-1?
Two metabolites can promote the function of PFK-1:
(1) AMP/ADP
(2) Fructose 2,6-bisphosphate
Two metabolites can inhibit the function of PFK-1:
(1) ATP
(2) Citrate
What can regulate Pyruvate kinase?
(1) Fructose 1,6-bisphosphate can promote it
(Feedforward activator)
(2) ATP can inhibit it
Give an example of feed forward regulation in the glycolysis process
Fructose 1,6-bisphosphate, which is a product of step 3 in glycolysis, can promote Pyruvate kinase, which is the enzyme responsible for step 10
This is really fascinating because step 3 is the committed step. Right after that we are sure we are in for glycosis instead of other pathway, the product can regulate downstream enzyme. Beutiful and magical nature.
Is Glucokinase (Hexokinase four) inhibited by G6P?
No.
The other three is inhibited, which makes glucokinase special
Does Glucokinase have a higher or lower Km lever of glucose vs other hexokinases?
Higher
Thus, activity continue to increase with increasing concentration of available glucose
ATP is one of the substrates for PFK-1, what is the other role it plays for PFK-1?
It is an allosteric inhibitor
Thus, ATP itself have contradicting influence on the phosphorylation of fructose 6-phosphate.
As substrate, the higher level of ATP, the stronger the reaction is. However, as allosteric inhibitor, the higher the level of ATP, the weaker the reaction is. This delicate regulation ensures that no waste will happen. If the ATP level is already high enough, then there is no need to further promote the reaction
Now, it is natural to understand that why AMP and ADP are allosteric activators for PFK-1
What is the role that Citrate play on PFK-1
It is a feedback inhibitor
High concentration of Citrate indicates that what happens to the citric acid cycle?
It indicates that the cycle is blocked
Is Fructose 2,6-bisphosphate a metabolite in glycolysis?
No
In Entner-Doudoroff pathway, what enzyme is absent?
PFK-1; thus, no fructose 1,6-bisphosphate formation
In Entner-Doudoroff pathway, is the triose stage still continued?
Yes
What are the two products in the Entner-Doudoroff pathway?
(1) Pyruvate
(2) G3P (will continue in the triose stage)
The Entner-Doudoroff pathway generates fewer ATP than glycolysis, why?
Because there is one 3C molecule that is directly turned to pyruvate and can not go through the process in step 10 that generates 1 ATP when turning PEP to Pyruvate. In Glycolysis, the net ATP gain is 2 per glucose, but the net gain of Entern-Doudoroff Pathway is only 1 per glucose
What is FDG used in the Positron Emission Tomography (PET)?
Fluorodeoxyglycose, It is a molecular probe that contains a neutron-deficient, radioactive element (e.g.F)
Tumor cells have very strong signal in PET due to high activities of what activity?
Glycolysis
