PAK262_002

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GLUCOSE CATABOLISM

GLYCOLYSIS Lecture 002

Learning outcomes

Dr. rer.nat. Syafrizayanti 2

Menguraikan jalur katabolisme glukosa dan regulasinya

Menjelaskan metabolisme heksosa selain glukosa

Menjelaskan tahap-tahap reaksi jalur pentosa fosfat

2. Katabolisme glukosa 2.1 Pendahuluan glikolisis

2.2 Reaksi-reaksi jalur glikolisis

2.3 Metabolisme anerobik piruvat

2.4 Pengaturan jalur glikolisis

2.5 Metabolisme heksosa lainnya

2.6 Jalur pentosa fosfat

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Overview of metabolism

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Major pathways of glucose ulizaon

Dr. rer.nat. Syafrizayanti 4 3/2/15

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Two phases of glycolysis


Preparatory or investment

Pay-off or generation


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Phosphorylaon of glucose


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Conversion of Glucose 6-Phosphate to Fructose 6-Phosphate


The phosphohexose isomerase reacon


glucose

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Phosphorylaon of Fructose 6-Phosphate to Fructose 1,6-Bisphosphate


Cleavage of Fructose 1,6-Bisphosphate


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The class I aldolase reaction (animal and plant)

catalyze reactions that proceed through neutral Schiff base or enol intermediates

The class II aldolases reaction (in bacterial) use a metal ion to stabilize the negative charge on an enolate intermediate

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Interconversion of the Triose Phosphates


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Oxidaon of Glyceraldehyde 3-Phosphate to 1,3-Bisphosphoglycerate



The glyceraldehyde 3-phosphate dehydrogenase reaction.

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Phosphoryl Transfer from 1,3-Bisphosphoglycerate to ADP

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Conversion of 3-Phosphoglycerate to 2-Phosphoglycerate


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The phosphoglycerate mutase reaction

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Dehydraon of 2-Phosphoglycerate to Phosphoenolpyruvate


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Transfer of the Phosphoryl Group from Phosphoenolpyruvate to ADP

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Glycolysis overall reaction

Note: the NADH formed in the process must be continually reoxidized to keep the pathway supplied with its primary oxidizing agent, NAD+ .


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Metabolic fate of NADH and pyruvate


NADH is energy - two possible fates: If O2 is available, NADH is re-oxidized in

the electron transport pathway, making ATP in oxidative phosphorylation

In anaerobic conditions, NADH is re-oxidized by lactate dehydrogenase (LDH), providing additional NAD+ for more glycolysis

Pyruvate is also energy - two possible fates:

aerobic: citric acid cycle anaerobic: LDH makes

lactate

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Under aerobic condions the pyruvate is completely oxidized via the citric acid cycle to CO2 and H2O.


Under anaerobic condions pyruvate must be converted to a reduced end product in order to reoxidize the NADH produced by the GAPDH reaction, there are two ways:


homolactic fermentation

alcoholic fermentation

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Homolacc Fermentaon Converts Pyruvate to Lactate


Alcoholic Fermentaon Converts Pyruvate to Ethanol and CO2


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Cellular glycolysis regulaon



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A comparison of G for the reacons of glycolysis

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Metabolism of hexoses other than glucose

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The pentose phosphate pathway


Group discussion

1. Describe how fructose, galactose, and mannose enter the glycolytic pathway

2. Summarize the reaction of each stage of the pentose

phosphate pathway


PAK262_002

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