Question

31. Acetoacetate and B-hydroxybutrate (ketone bodies) can provide a source of fuel (energy) in some tissues a). (2 pts) Does the synthesis of p-hydroxybutyrate require NAD or NADH (circle the correct choice)? он H2 I H2 11 OOC-o B-Hydroxybutyrate acetoacetate b). (2 pts) Is the synthesis of ß-hydroxybutyrate favorable? (See Table 1). Provide support for your answer (points will not be given without this). 0.(3 pts) Calculate the AG for this reaction using Table 1. Make certain to include units. Table 1. Some Standard Reduction Potentials Half reaction Acetoacetate + 2H +2eB-hydroxybutyrate -0.346 NAD+2e-NADH -0.32

Answer 1

A) β-oxidation {NADH/NAD } ----------- Malate to OA 2.

OA is also used by gluconeogenesis.

3. Acetyl CoA is an allosteric activator of pyruvate carboxylase.

Pyruvate ---PC-------- OA

But pyruvate concentration is low due to decreased glycolysis as in starvation & DM

B) The three ketone bodies are ¾Acetoacetate, β-Hydroxy butyrate and Acetone. Ketone bodies are produced from acetyl-CoA, mainly in the mitochondrial matrix of liver cells when carbohydrates are so scarce that energy must be obtained from breaking down of fatty acids.

Ketone Bodies as Fuel

water soluble transported across the inner mitochondrial membrane as well as across the blood-brain barrier and cell membranes.

Source of fuel for brain, heart and muscle

Major energy source(75%) for brain during starvation

Ketone bodies are transported from the liver to other tissues, where acetoacetate and β-hydroxybutyrate can be reconverted to acetyl-CoA to produce energy.

The heart gets much of its energy from ketone bodies, although it also uses a lot of fatty acids