Question

Propose a reason for gluconeogenesis needing different steps.?

Answer 1

• Gluconeogenesis occur in mitochondria or cytoplasm depending on the type of substrate used.
• If there is glucose starvation, pyruvate may enter the gluconeogenesis pathway.
• Gluconeogenesis occurs mainly in liver (about 90%) and some in kidneys (10%)
• 2 Pyruvate + 4ATP + 2GTP + 2NADH +6H2O - > Glucose + 4ADP + 2GDP + 6Pi + 2NAD+ + 2H+

• The glycolytic pathway, is regulated by concentration of sugar (glucose), certain enzymes, some products formed during the pathway itself, hormones (insulin/ glucagon), ATP/ADP/AMP,
• Phosphofructokinase (PFK) plays the key role in the regulation of glycolysis, though hexokinase controls the initial glycolytic step.
• The first irreversible reaction in glycolytic pathway (the slowest and rate limiting step) is phosphorylation reaction mediated by PFK

• Gluconeogenesis is favoured by accumulation of Acetyl co A and pyruvate.
• Breakdown of fatty acid enhances acetyl co A accumulation.
• Also, gluconeogenesis may be considered as reverse process of glycolysis, but the irreversible steps needs to be bypassed.
• Thus, decreasing glycolytic pathway is essential, which is mediated by accumulation of certain glycolysis intermediates, or blocking enzymes that promotes glycolysis.

• Thus, different bypass reactions are required for gluconeogenesis process.This results in excess and overall large delta G value.

• Thus, several steps are required for gluconeogenesis, to bypass the regulatory steps of glycolysis.