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Feeder Pathways
Feeder pathways are metabolic routes that provide substrates for central
metabolic pathways like glycolysis and the citric acid cycle.They include
pathways such as
glycogenolysis, and
the pentose phosphate
pathway.
Gluconeogenesis
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Gluconeogenesis is the synthesis of glucose from non-carbohydrate
precursors, primarily occurring in the liver and kidneys.
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It involves reversing glycolysis, with some unique steps to bypass
irreversible reactions.
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The first step is catalyzed by
pyruvate carboxylase, converting pyruvate to oxaloacetate in the mitochondria.
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Oxaloacetate is then converted to phosphoenolpyruvate by
PEP carboxykinase.
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The rate limiting step is catalyzed by
fructose-1,6-bisphosphatase.
Dive deeper: Alanine and glutamine are amino acids that
contribute to gluconeogenesis by
serving as precursors for pyruvate and oxaloacetate, respectively. During
periods of fasting or intense exercise, these amino acids can be released
from muscle tissue and transported to the liver, where they are converted
into glucose to help maintain blood sugar levels. Gluconeogenesis occurs
in the cytoplasm of the cell. In
addition to nucleotide synthesis, the pentose phosphate pathway generates
NADPH and ribose-5-phosphate, which are essential for
fatty acid synthesis and nucleotide
synthesis.
Practice Questions
Which of the following is found in gluconeogenesis but not glycolysis? Type the letter of your answer: C
a. Pyruvate
b. Fructose-1,6-bisphosphate
c. Oxaloacetate
d. Phosphoenolpyruvate
Which best describes the difference between gluconeogenesis and glycolysis? Type the letter of your answer: B
a. Gluconeogenesis is the breakdown of glucose, while glycolysis is the synthesis of glucose.
b. Gluconeogenesis synthesizes glucose from non-carbohydrate precursors, while glycolysis breaks down glucose into pyruvate.
c. Gluconeogenesis occurs in the mitochondria, while glycolysis occurs in the cytoplasm.
d. Gluconeogenesis is a catabolic pathway, while glycolysis is an anabolic pathway.
What is the primary role of the pentose phosphate pathway? Type the letter of your answer: A
a. To synthesize nucleotides and fatty acids
b. To synthesize carbohydrates and nucleotides
c. To synthesize fatty acids and carbohydrates
d. To produce ATP and GTP