Energy needs, brain

Ketones in starvation increase the amount of O2 needed to burn fuel to CO2 (CO2 / O2) only a small amount as compared to fats. The energy yield per carbon for ketones is similar to glucose. The brains energy needs and O2 availability can be met nearly as well by ketones, as by glucose. (Table 10.3). 

The energy needed to transport ions across the membrane is obtained by the cell in chemical reactions occurring in it that is, the oxidation of organic substances with oxygen (for more details, see Section 30.2). Every second about 10 to 10 ions are transported across 1 m of membrane area. This process requires 20 to 30% of all energy generated by the cell. It has been calculated that the total power of the ionic pumps in the cells of the brain is about 1 watt. 

E. The energy needs of the brain and other glucose-requiring organs are satisfied during the post-absorptive period through provision of glucose by the liver. 

Net glycogen breakdown enables the liver to secrete glucose to provide for the energy needs of much of the body, particularly the brain. 

Symptoms of PDH deficiency include weakness, ataxia, and psychomotor retardation due to damage to the brain, which is the organ most reliant on the TCA cycle to supply its energy needs. 

Brain tissue does not contribute to the energy needs of other tissues. Rather, it makes major demands on the glucose supply, accounting for upwards of 50% of the glucose con-... 

This inequality means that a maximal net rate of ATP production is incompatible with the optimal efficiency. Cellular pathways balance the rate and efficiency of ATP production with respect to the energy needs of the cell. For example, heart and brain mitochondrial systems utilize more oxygen and produce ATP at a faster rate than the... 

The metabolic patterns of the brain, muscle, adipose tissue, kidney, and liver are strikingly different. Let us consider how these organs differ in their use of fuels to meet their energy needs ... 

How does the liver meet its ovm energy needs a-Ketoacids derived from the degradation of amino acids are the liver s own fuel. In fact, the main role of glycolysis in the liver is to form building blocks for biosyntheses. Furthermore, the liver cannot use acetoacetate as a fuel, because it has little of the transferase needed for acetoacetate s activation to acetyl CoA. Thus, the liver eschews the fuels that it exports to muscle and the brain. 

Glycogen is a minor energy store. The amount stored in the body is sufficient to supply the energy needs of the brain for only 3 days of fasting. Clearly, the energy value of the nutrients in the bloodstream itself is minimal. 

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