SA Gluconeogenesis

Question 1

What is gluconeogenesis, and what useful purposes does it serve in people?

Answer 1

Gluconeogenesis is the biosynthesis of glucose from simpler, noncarbohydrate precursors such as oxaloacetate or pyruvate. During periods of fasting, when carbohydrate reserves have been exhausted, gluconeogenesis provides glucose for metabolism in tissues (brain, erythrocytes) that derive their energy primarily from glucose metabolism.

Question 2

In gluconeogenesis, how do animals convert pyruvate to phosphoenolpyruvate? Show structures, enzymes, and cofactors.

Answer 2

yruvate is converted into phosphoenolpyruvate in two steps: (1) Pyruvate + HCO − + ATP → oxaloacetate + ADP + Pi
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(2) Oxaloacetate + GTP → CO2 + GDP + phosphoenolpyruvate
The first reaction is catalyzed by pyruvate carboxylase, which requires biotin as a cofactor; the second, by phosphoenolpyruvate carboxykinase. [See Fig. 20-3, p. 727].

Question 3

What are the biological functions of the pentose phosphate pathway?

Answer 3

he pentose phosphate pathway produces pentose phosphates (for nucleotide synthesis) and NADPH (reducing agent for biosynthetic processes).