Lecture_15_3-11-10-PDF_41129

Lecture_15_3-11-10-PDF_41129 - Reminder Most fatty acids...

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Most fatty acids have even numbers of carbon atoms (condensation of C2 units, We will learn in Chapter 19-4) Therefore most of them are completely converted to acyl-CoA b -oxidation b a b a Reminder
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However, some plants and marine organisms synthesize aftty acids with an odd number of carbon atoms Once down to the three carbon , more reaction steps require Reminder
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Once down to the three carbon, propionyl CoA, a biotin carboxylase is needed to put a CO 2 on the carbon backbone. The mutase arranges Methylmalonyl-CoA to succinate CoA , using a vitamin B12 containing enzyme. Note the stereo specific requirement for the mutase
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Page 692 The mutase arranges Methylmalonyl-CoA to succinate CoA , using a containing enzyme.
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Figure 20-17 Vitamin B12 (derivative of cobalamin) The Nobel Prize in Chemistry 1964 "for her determinations by X-ray techniques of the structures of important biochemical substances" Dorothy Crowfoot Hodgkin United Kingdom University of Oxford, Royal Society Oxford, United Kingdom b. 1910 d. 1994 Box 20-2, p697
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High Density Lipoproteins ( HDL ) = good Low Density Lipoproteins ( LDL ) = bad Good and Bad " blood cholesterol levels Reminder
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3. Ketone bodies 4. Fatty Acid Biosynthesis A. Transport of mt acetyl-CoA into the cytosol B. Aceyl-CoA Carboxylase C. Fatty acid synthase D. Elongases and Desaturases E. Synthesis of Triacylglycerols Lec15
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Ketone Bodies Soluble form of energy derived from fats by the liver. Brain adjusts to use ketone bodies for energy after several days of starvation.
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Substances with a molecular weight higher than 500 daltons generally cannot cross the blood-brain barrier (BBB) , while smaller molecules often can. Blood-Brain Barrier BBB blocks all molecules except those that cross cell membranes by means of lipid solubility (such as oxygen, carbon dioxide, ethanol, and steroid hormones) and those that are allowed in by specific transport systems (such as ketone bodies , sugars and some amino acids).
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Fatty acids can be used as the major fuel for tissues such as muscle, but they cannot cross the blood-brain barrier , and thus cannot be used by the central nervous system (CNS)*. This becomes a major problem during starvation (fasting), particularly for organisms such as ourselves in which CNS metabolism constitute a major portion of the resting basal metabolic rate. What is needed is an alternate fuel source based on fat rather than muscle. The so-called ketone bodies serve this function. *Note that brain is 2% of body weight but uses 12% of body energy
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Ketone bodies Derived from fatty acid degradation they can be converted to citric acid intermediates . Acetone is not available as fuel to any significant extent, and is thus a waste product .
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A ketone is either the functional group characterized by a carbonyl group (O=C) linked to two other carbon atoms or a chemical compound that contains this functional group.
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This note was uploaded on 09/15/2010 for the course BCHS 3305 taught by Professor Fujita during the Spring '10 term at University of Houston.

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Lecture_15_3-11-10-PDF_41129 - Reminder Most fatty acids...

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