4. (20 pts) There is a difference in the way that oligosaccharides are degraded

Question

4. (20 pts) There is a difference in the way that oligosaccharides are degraded (reduced to monosaccharide size) prior to entering glycolysis. a) What are the reactants and products (in words not structures) when polysaccharide phosphorylase is used to degrade glycogen? b) What additional reaction does the product of polysaccharide phosphorylase require before it proceeds into the steps in glycolysis? c) Is there any advantage to degrade an oligosaccharide by polysaccharide phosphorylase rather than by hydrolysis? d) Why aren't dietary starches (amylose or amylopectin) degraded by polysaccharide phosphorylase?

Explanation / Answer

1. Glycogen phosphorylase yields glucose 1-phosphate(product) by cleaving glycogen(substrate) by the addition of orthophosphate. Phosphorylase catalyzes the removal of glycosyl residues from the ends with a free 4-OH group of glycogen molecule. Orthophosphate cleaves the glycosidic linkage among the C-1 carbon atom and the glycosidic oxygen atom which helps in retaining the ? configuration at C-1.

2. Glycogen phosphorylase induces phosphorolytic cleavage of glycogen and produces glycogen-1-phosphate. a non-reducing terminus is removed when cleavage of glucose is done from glycogen. Furthermore, if the glucose-1-phosphate generated from glycogen is converted into glucose-6-phosphate by phosphoglucomutase, it can continue straight to glycolysis.the immediate advancement to glycolysis causes ATP consumption exclusion which is essential for converting glucose to G6P. three ATPs are produced if the glucose produced from glycogen is used by glycolysis.

3. the application of phosphorolysis to metabolize glycans is essentially more energetically advantageous for cells than hydrolysis considering the discharged sugar - 1 - phosphates feed immediately into the glycolysis metabolic pathway without the expenditure of ATP

4. due to the linearity of Amylose it only holds one non-reducing end that glycogen phosphorylase can work on. While glycogen has various branches where glycogen phosphorylase can work on. so, Amylose would demand extra time to break down, as it is linear, therefore it is not a suitable source of energy for immediate mobilization of glucose.

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