Biochemistry Glycolysis/Gluconeogenesis

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In summary, reactions b and e are blocked because they involve the enzyme pyruvate carboxylase, which requires biotin as a cofactor. This is important for the conversion of pyruvate to oxaloacetate and ultimately glucose. The other reactions are not affected by avidin because they do not involve biotin enzymes.
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JOJOwwwAiri
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Homework Statement
Avidin, a 70-kd protein in egg white, has very high affinity for biotin. In fact, it is a highly specific inhibitor of biotin enzymes. Which of the following conversions would be blocked by the addition of avidin to a cell homogenate?
(a) Glucose & pyruvate
(b) Pyruvate & glucose
(c) Oxaloacetate & glucose
(d) Malate & oxaloacetate
(e) Pyruvate & oxaloacetate
(f) Glyceraldehyde 3-phosphate & fructose 1,6-bisphosphate
Relevant Equations
N/A
The answer is that reactions in parts b and e would be blocked but I don't understand why the answer is that and what's the logic involved in getting the correct answer. Could somebody explain the general approach in understanding and solving this type of question to me? Thanks in advance!
 
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I guess the answer requires knowing two key facts:
1) The enzyme pyruvate carboxylase (which converts pyruvate to oxaloacetate) uses biotin as a cofactor (hence reaction e is blocked).
2) For pyruvate to be converted to glucose (via gluconeogenesis), pyruvate must be able to be converted to oxaloacetate via pyruvate carboxylase (so reaction b is also blocked).

The other reactions are not catalyzed by biotin enzymes and hence would not be affected by avidin.
 

FAQ: Biochemistry Glycolysis/Gluconeogenesis

What is the purpose of glycolysis and gluconeogenesis in the body?

Glycolysis is the process by which glucose is broken down into smaller molecules to produce energy in the form of ATP. Gluconeogenesis, on the other hand, is the process by which glucose is synthesized from non-carbohydrate sources. Both processes are essential for providing the body with a constant supply of glucose, which is the main source of energy for cells.

What are the key enzymes involved in glycolysis and gluconeogenesis?

The key enzymes involved in glycolysis are hexokinase, phosphofructokinase, and pyruvate kinase. These enzymes catalyze the breakdown of glucose into pyruvate. In gluconeogenesis, the key enzymes are glucose-6-phosphatase, fructose-1,6-bisphosphatase, and phosphoenolpyruvate carboxykinase. These enzymes catalyze the synthesis of glucose from non-carbohydrate sources.

How is the regulation of glycolysis and gluconeogenesis controlled?

The regulation of glycolysis and gluconeogenesis is controlled by various hormones and enzymes. Insulin stimulates glycolysis and inhibits gluconeogenesis, while glucagon has the opposite effect. Enzymes involved in these processes are also regulated by allosteric regulation and covalent modification, such as phosphorylation.

What is the role of ATP in glycolysis and gluconeogenesis?

ATP is a crucial molecule in both glycolysis and gluconeogenesis. In glycolysis, ATP is produced through substrate-level phosphorylation, where a phosphate group is transferred from a substrate to ADP to form ATP. In gluconeogenesis, ATP is required for the synthesis of glucose from non-carbohydrate sources.

How does the regulation of glycolysis and gluconeogenesis contribute to metabolic disorders?

Imbalances in the regulation of glycolysis and gluconeogenesis can contribute to metabolic disorders such as diabetes. In diabetes, there is a deficiency of insulin, leading to increased gluconeogenesis and decreased glycolysis, resulting in high blood glucose levels. On the other hand, overactive glycolysis and underactive gluconeogenesis can also lead to metabolic disorders such as hypoglycemia.

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