1 chapter 17: oxidation of fatty acids keystone concepts the insolubility of triglycerides in...
DESCRIPTION
3 How are dietary lipids processed?TRANSCRIPT
![Page 1: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/1.jpg)
1
Chapter 17: Oxidation of Fatty Acidskeystone concepts
• The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated
• Fatty acids are oxidized in the mitochondria• Fatty acids must be transported across the inner mitochondrial
membrane• Oxidation of fatty acids in the mitochondria has three stages • Oxidation of unsaturated and odd chain fatty acids requires
additional reactions• In mammals, an alternative pathway for acetyl-CoA produces
ketone bodies
![Page 2: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/2.jpg)
Emulsification
• Fats are not water soluble
• Made soluble by bile salts (amphipathic) that are made in the liver and stored in the gall bladder
• Converted to mixed micelles of bile salts and triacylglycerols
![Page 3: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/3.jpg)
3
How are dietary lipids processed?
![Page 4: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/4.jpg)
Fat Metabolism
I’m not fat, I’ve just got a lot of potential energy!
![Page 5: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/5.jpg)
Fatty Acids and Energy• Fatty acids in triglycerides are the principal
storage form of energy for most organisms.– Hydrocarbon chains are a highly reduced form of
carbon.– The energy yield per gram of fatty acid oxidized is
greater than that per gram of carbohydrate oxidized.
![Page 6: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/6.jpg)
Beta Oxidation
The break down of a fatty acid to acetyl-CoAunits…the ‘glycolysis’ of fatty acids
Occurs in the mitochondria
STRICTLY AEROBIC
Acetyl-CoA is fed directly into the Krebs cycle
![Page 7: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/7.jpg)
Activation and Transported to Mitochondria
• FA + CoA + ATP fatty acyl-CoA + AMP + 2Pi
• Coupled to the cleavage of ATP
• Acyl CoA Synthetase – a family of isozymes specific for short, medium and long chain FA that catalyze production of fatty acyl-CoA
• Transported through inner mitochondrial membrane via carnitine– uses specific acyl carnitine transporter
![Page 8: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/8.jpg)
Beta Oxidation
• Breakdown of fats into – Acetyl coenzyme A --> Krebs Cycle– FADH2 --> Oxidative Phosphorylation– NADH--> Oxidative Phosphorylation
• Breaks off two carbons at a time to acetyl CoA
![Page 9: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/9.jpg)
9
b-oxidation –first of three stages of fatty acid oxidation
![Page 10: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/10.jpg)
10
4 Steps of b-oxidation1. Dehydrogenation of the fatty acyl-CoA to
make a trans double bond between α and β carbon.• Short, medium, and long chain acyl-CoA
dehydrogenases• e- removed transferred to FAD
2. Hydration of the double bond
3. Dehydrogenation of the b-hydroxyl group to a ketone
- e- removed transferred to NAD+
4. Acylation – addition of CoA and production of acetyl-CoA
Step 1
Step 2
Step 3
Step 4
![Page 11: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/11.jpg)
Energy Yield from b-Oxidation • Yield of ATP per mole of stearic acid (C18).
![Page 12: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/12.jpg)
Ketone Bodies• Ketone bodies: acetone, b-hydroxybutyrate, and
acetoacetate;– are formed principally in liver mitochondria.– can be used as a fuel in most tissues and organs.
• Formation occurs when the amount of acetyl CoA produced is excessive compared to the amount of oxaloacetate available to react with it and take it into the TCA; for example:– intake is high in lipids and low in carbohydrates.– diabetes is not suitably controlled.– starvation.
![Page 13: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/13.jpg)
13
ketone bodies: another fate for acetyl-CoA
• Formed in the liver• Exported• Oxidized in citric acid cycle• Step 1: thiolase reversed – joins 2
acetyl-CoA• Step 2: acetyl-CoA condensation• Step 3: cleavage of acetyl-CoA • Step 4: reduction or
decarboxylation
![Page 14: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/14.jpg)
14
ketone bodies provide energy
![Page 15: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/15.jpg)
15
Amino acid oxidation
keystone concepts:• Dietary proteins - primary source of biologically useful N in
animals
• Amino groups transferred to α-ketoglutarate forming glutamate and an α-keto acid
• Deaminated amino acids produce carbon skeletons that enter the citric acid cycle
• Most amino acids are glucogenic, some are both glucogenic and ketogenic,
just 2 are solely ketogenic
![Page 16: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/16.jpg)
16
amino acid oxidation• How much energy do organisms derive from amino acids?
• That depends upon the organism
Carnivores (~90% after a meal)
Humans (10-15%)
• What distinguishes amino acid catabolism from the oxidative processes discussed thus far?
• Every amino acid contains an amino group; amino acid oxidation produces high quantities of toxin: Ammonia – NH4
+
![Page 17: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/17.jpg)
N balance = Nin - Nout
1. AA are used for Protein Synthesis & N containing compounds
2. AA in excess are degraded (used for energy)N is disposed of in urea (80%) or creatinine
![Page 18: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/18.jpg)
Positive Nitrogen Balance
![Page 19: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/19.jpg)
Negative Nitrogen Balance
1. Stress
2. Decreased Intake
3. Lack of an essential AA
![Page 20: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/20.jpg)
20
we cannot make essential amino acids
![Page 21: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/21.jpg)
Metabolic Pool of Amino Acids
• Metabolic pool AA has no storage form in mammals (as with other life forms) as free AA or as specialized storage form (such as glycogen for glucose, TG for FA) but a certain percentage of muscle & structural proteins are “expendable”.
• AA are used for proteins, N compounds, energy (also via glucose) but increased protein breakdown will eventually compromise normal protein function.
• Therefore need a small mobile pool of free AA in cells and blood
![Page 22: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/22.jpg)
22
Dietary proteinis degraded toamino acids
Proteases in the stomach and small intestine
Peptidases at the intestinal mucosa
![Page 23: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/23.jpg)
Protein CatabolismOverview of Protein catabolism.
![Page 24: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/24.jpg)
24
first step in amino acid oxidation• Removal of the amino group• Formation of an a-keto acid• How?• Aminotransferases (transaminases)• Collects the amino groups from many amino acids in
the form of L-glutamate amino group carrier
![Page 25: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/25.jpg)
25
nitrogen excretion: urea cycle
![Page 26: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/26.jpg)
Amino Acid Catabolism
• The breakdown of amino acid carbon skeletons follows two pathways.– glucogenic amino acids: those whose carbon
skeletons are degraded to pyruvate or oxaloacetate, both of which may then be converted to glucose by gluconeogenesis.
– ketogenic amino acids: those whose carbon skeletons are degraded to acetyl CoA or acetoacetyl CoA, both of which may then be converted to ketone bodies.
![Page 27: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/27.jpg)
Major Functions of Amino Acids Derived from Dietary Protein
OxidationGlycogenic amino acids: --Blood glucose--EnergyKetogenic amino acids: -Acetyl CoA-Stored fat-Energy
Biosynthesis of nitrogen-containing metabolites
Heme Blood cellCholine PLGlycosamine SugarNucleotides DNAProtein synthesis ProteinBiogenic amines NeurotransmittersCarnitine HeartCreatine phosphate « Energy »
![Page 28: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/28.jpg)
Amino Acid Catabolism• Catabolism of AA carbon skeletons.
![Page 29: 1 Chapter 17: Oxidation of Fatty Acids keystone concepts The insolubility of triglycerides in dietary lipids and adipose tissue must be accommodated Fatty](https://reader035.vdocuments.net/reader035/viewer/2022062311/5a4d1b777f8b9ab0599b7793/html5/thumbnails/29.jpg)
Amino Acid Catabolism