Biochemistry Book Chapter 7

[krybczy1]

Hello, there is one particular statement on page 159 of the Biochem textbook that I am confused about. The sentence reads "In liver cells, the glucose stored in glycogen is primarily mobilized for gluconeogenesis when blood glucose levels are low"... I am confused because I thought that these are two separate processes, one in which glycogen reserves are broken down first to regulate blood glucose levels, and once depleted, gluconeogenesis takes over starting from noncarbohydrate precursors to create new glucose molecules to maintain blood glucose homeostasis.

[NS_Tutor_Alex]

Hi krybczy1,

Great question here! You're correct in your understanding of what occurs in times of low glucose in the blood stream, that being the breakdown of glycogen in order to export glucose to the blood stream. In breaking down glycogen, Glucose-1-phosphate is produced and then is converted to G-6-P by phosphoglucomutase. At this point, the fate of G-6-P is uncertain as it could go into glycolysis, the pentose phosphate pathway or, G-6-P can be dephosphorylated, producing glucose which is then exported to the bloodstream. If this occurs, it is an example of gluconeogenesis, just not the traditional pathway we think about when we hear or see that word.

Hope that helps!

Alex

[krybczy1]

That makes a lot more sense, thank you!