![CONTD
2,3-BPG, the most concentrated
organophosphate in the
erythrocyte, forms 3-PG by the
action of bisphosphoglycerate
phosphatase.
The concentration of 2,3-BPG varies
inversely with the [H+], which is
inhibitory to catalytic action of
bisphosphoglyceromutase.](https://image.slidesharecdn.com/carbohydratemetabolismday1-150827043835-lva1-app6891/75/Carbohydrate-metabolism-part-1-26-2048.jpg)
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Carbohydrate metabolism, part 1
- 1. INTERMEDIARY METABOLISM OF CARBOHYDRATES (DAY:1:INTRODUCTION & GLYCOLYSIS) Dr. Ifat Ara Begum Assistant Professor Dept. of Biochemistry Dhaka Medical College Dhaka
- 2. INTRODUCTION It denotes thevarious biochemical processes responsible for the formation, break down and interconversion of carbohydrates in living organisms. The most important carbohydrate is glucose
- 3.
- 5. METABOLIC PATHWAYS FOR CARBOHYDRATES Anabolicpathways: Glycogenesis, Gluconeogenesis, Lipogenesis, Uronic acid pathway. Catabolic pathways: Glycolysis, Oxidation of pyruvate to acetyl co A, TCA cycle, Glycogenolysis, HMP shunt. Amphibolic pathway: TCA cycle
- 7. 1. GLYCOLYSIS/ EMBDEN- MEYERHOF-PARNASPATHWAY The stepwise degradation of glucose (and other simple sugars) It is unique in that it can function either aerobically or anaerobically, depending on the availability of oxygen and ETC It is the paradigm (synonym. model) of metabolic pathways
- 8. CONTD This pathway that converts glucose(or glycogen) into pyruvate in aerobic condition and lactate in anaerobic condition. It is a determined sequence of ten enzyme-catalyzed reactions. The intermediates provide entry points to glycolysis. most monosaccharides (like fructose and galactose can be converted to one of these intermediates.
- 9. CONTD Substrate: Glucose/glycogen Product: Pyruvate(aerobically), Lactate (anaerobically) Site: Almost all tissues Compartment: Cytosol Nature: Catabolic Rate limiting enzyme: PFK Hormonal control: Insulin (+), Glucagon (-)
- 10. CONTD The entire glycolysispathway can be separated into two phases: I. The Preparatory Phase – in which ATP is consumed and is hence also known as the investment phase. The first 5 steps are regarded as preparatory phase II.The Pay Off Phase – in which ATP is produced. The last 5 steps are regarded as pay off phase
- 11.
- 12. II) PAY OFFPHASE
- 14. ANAEROBIC GLYCOLYSIS Occurs incells lack of mitochondria like RBC, leucocytes, renal medulla, lens, cornea. Here, pyruvate is reduced by NADH to lactate by LDH. The NADH utilized in this step is obtained from the reaction catalyzed by glyceraldehydes 3 PO4 dehydrogenase .
- 15. CONTD C C CH3 O− O O C HC CH3 O− OH O NADH + H+ NAD+ LactateDehydrogenase pyruvate lactate
- 16. CONTD The formation oflactate allows NAD to be reused by glyceraldehydes 3 PO4-DH, so that glycolysis proceeds even in the absence of O2. The occurrence of uninterrupted glycolysis is very essential in skeletal muscles during strenuous exercise where O2 supply is limited.
- 17. CONTD Lactate serves asa fuel source for cardiac muscle as well as brain neurons. Astrocytes, which surround and protect neurons in the brain, ferment glucose to lactate and release it. Lactate taken up by adjacent neurons is converted to pyruvate that is oxidized via Krebs Cycle.
- 18. BASIC PROCESSES INVOLVEDIN GLYCOLYSIS
- 19. WHY G-6-P ISFORMED?
- 21. FATE OF G-6-PO4 Itis an important compound at the junction of several metabolic pathways: Glycolysis Gluconeogenesis Pentose phosphate pathway Glycogenesis Glycogenolysis
- 24. LUEBERING-RAPOPORT PATHWAY It is abiochemical pathway in mature erythrocyte involving the formation of 2.3-bisphosphoglycerate and which regulates oxygen release from Hb and delivery to tissues. It is also called Luebering-Rapoport shunt. 2,3-BPG combines with Hb and reduces affinity for O2.
- 25. CONTD The normal glycolyticpathway generates 1,3-BPG, which may be dephosphorylated by phosphoglycerate kinase (PGK), generating ATP But it may be shunted into the Luebering- Rapoport pathway, where bisphosphoglycerate mutase catalyzes the transfer of a phosphoryl group from C1 to C2 of 1,3- BPG, giving 2,3-BPG.
- 26. CONTD 2,3-BPG, the mostconcentrated organophosphate in the erythrocyte, forms 3-PG by the action of bisphosphoglycerate phosphatase. The concentration of 2,3-BPG varies inversely with the [H+], which is inhibitory to catalytic action of bisphosphoglyceromutase.
- 27.
- 28. IMPORTANCE OF 2,3-BPG When2,3-BPG binds to deoxyhemoglobin (The form of hemoglobin without oxygen), it acts to stabilize the low oxygen affinity state (T state) of the oxygen carrier. By selectively binding to deoxyhemoglobin, 2,3- BPG stabilizes the T state conformation, making it harder for oxygen to bind hemoglobin and more likely to be released to adjacent tissues. 2,3-BPG is part of a feedback loop that can help prevent tissue hypoxia in conditions where it is most likely to occur.
- 29. CONTD Conditions of lowtissue oxygen concentration such as high altitude (2,3- BPG levels are higher in those acclimated to high altitudes), airway obstruction, or congestive heart failure will tend to cause RBCs to generate more 2,3-BPG in their effort to generate energy by allowing more oxygen to be released in tissues deprived of oxygen. Ultimately, this mechanism increases oxygen release from RBCs under circumstances where it is needed most.
- 30. CONTD This release ispotentiated by the Bohr effect in tissues with high energetic demands. Bohr effect is another useful way to solve the affinity problem of the hemoglobin, and it is related to the pH and the CO2. It’s important to highlight that the behavior of myoglobin doesn’t work in the same way, as 2,3-BPG has no effect on it.