This week is all about glycolysis…… It is a bit difficult to grasp at first but with a little time and alot of drawing you would get it!!!!!!!
All tissues use the glycolytic pathway for the breakdown of glucose to provide energy. This energy is in the form of ATP.
Glucose to pyruvate takes place in two stages these are:
The first five reactions of glycolysis correspond to an energy investment stage
The other five reactions of glycolysis constituted energy generating stage
Below shows a diagrammatic explanation of the steps in glycolysis it is simple yet effective.
The Fate of Pyruvate
Diagram showing the fate of pyruvate under different conditions:
Aerobic conditions
FATE NUMBER 1:
This is where pyruvate is converted to acetyl CoA. The enzyme pyruvate dehydrogenase (PDH) uses Thiamine prophosphate (TTP) to catalyse the reaction. It is irrevisible.
NOTE: The most ATP is generated in this fate.
Anaerobic conditions
These two fates can sometimes be referred to as fermentation.
This process helps regenerate NAD+.
FATE NUMBER 2
Pyruvate is converted to lactate by the enzyme lactate dehydrogenase (LDH).
FATE NUMBER 3
Pyruvate decarboxylase uses TPP to convert pyruvate to acetaldehyde
THEN
Using alcohol dehydrogenase acetaldehyde is convert to ethanol
NADH is converted to NAD+
NOTE: No ATP is generated.
Feeder Pathways for Glycolysis
In glycolysis most carbohydrates except glucose are transformed into one of the glycolytic intermediates:
1. The storage polysaccharides glycogen and starchh
2. The disaccharides maltose, lactose, trehalose and sucrose
3. The monosaccharides fructose, mannose and galactose
Metabolism of Fructose
takes place via two routes
1. Adipose tissue muscle and kidney
Fructose to (enzyme used is Hexokinase ) Fructose 6 phosphate
It can then undergo glycolysis
2. In the Liver
The enzyme used is glucokinase this does not phoshorylate the frustose. Here fructose is metabolised.
POINTS TO NOTE:
- Glycolysis takes place in the cytosol of cells.
- There are two phases in glycolysis these are: The Energy investment phase & Energy generation phase
- Glycolysis produces 2 pryuvate molecules.
- ATP is initially needed.
- ATP is generated.
- The fate of the pryuvate form differs depending on the conditions.
- There is a disease called Galactosemia which is a genetic disease caused by the inability of the body to convert galactose to glucose.
REFERENCES
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