Glycolysis And Gluconeogenesis Flashcards
What happens to pyruvate after it has been produced from glycolysis
It is further metabolised anaerobically to lactic acid (fermentation) or to ethanol (alcoholic fermentation)
What is glycogenolysis?
The breaking of glucose molecules one at a time from glycogen in the liver/muscle
What is the equation that summarizes the process of glycogenolysis?
(Glucose)n +Pi -> (glucose)n-1 + glucose 1-p
Glucose 1-p -> glucose 6-p
From there it’s either free glucose or it enters glycolysis
Describe glycogenolysis in the liver?
Glycogenolysis provides glucose for the blood stream
Glucose 6-p is mainly dephosphoryalted to free glucose
Describe glycogenolysis in muscle?
Glycogenolysis provides energy for the exercising muscle, the glycogen stores are broken down to produce glucose that enters the glycolysis pathway
What are the 2 enzymes at play in glycogen breakdown?
Glycogen phosphorylase
Phosphoglucomutase
What is phosphorolysis?
Addition of Pi followed by cleavage of the bond
Explain the role of the enzyme glucose-6-phosphatase?
It converts glucose 6-p -> glucose
In the liver, a phosphate group can be removed and glucose is released
Muscle does not contain Glucose-6-phosphatase
What is the ATP net gain in glycogenolysis?
3 ATP molecules as opposed to only 2 in glycolysis as the G-G6P is absent
What is gluconeogenesis?
The formation of glucose from non-carbohydrate sources
Typically occurs in liver and is not simple the reverse of glycolysis but some of the same enzymes are used
describe the steps in gluconeogenesis?
Pyruvate -> phosphoenolpyruvate
-> fructose 1,6- biphosphate -> fructose -6-phosphate -> glucose
What are the enzymes involved in gluconeogenesis and how do the molecules AMP and ATP affect them?
The conversion of fructose 1,6-biphopshate to fructose-6-phosphate requires the enzyme fructose 1,6 phosphatase
-ATP stimulates this but AMP inhibits it
What does PFK do in terms of gluconeogenesis?
Due to cycle (see diagram)
Conversion of fructose-6-phosphate to fructose 1,6-biphosphate requires PFK
AMP stimulates and ATP inhibits
Where can the non-carbohydrate sources be from in reference to gluconeogenesis?
From glycerol.
Also could be from amino acids (alanine,glutamine,aspartate) - go to liver and then pyruvate etc
Best source however is lactate, it can go to the liver and form new glucose
Where can pyruvate go?
Pyruvate can go to the TCA cycle
OR
pyruvate can go to lactate which is a process that regenerates NAD (NAD+) limits rapid glycolysis
The production of lactate restores what? And how?
It restores redox balance (regenerates NADH to NAD+)
This balances the NAD+ which was reduced to NADH during glycolysis
How is lactate formed?
LDH catalyses production of lactate (removes a hydrogen)
This process is higher in type 2 fibers
In vitro studies have shown that a low pH results in inhibition of what?
Phosphorylase
Hexokinase
Phosphofructokinase
Myosin ATPase is inhibited by IMP
what releases more energy, the conversion of pyruvate to lactate of oxidation of pyruvate to acetyl CoA?
The oxidation of pyruvate to acetyl CoA releases more energy which then feed to the TCA cycle
what is pyruvate dehydrogenase?
It is present in the mitochondrial matrix and is the rate limiting enzyme in the conversion of pyruvate to acetyl CoA. It forms part of the pyruvate dehydrogenase complex (PDH)
Pyruvate -> Acetyl CoA (generates NADH)
