Molecule Catabolism (Lec 4) Flashcards
Lipid Classification
- Lipids that contain fatty acids (complex lipids), further separated into storage lipids and membrane lipids
- Lipids that do not contain fatty acids (choleserol, vitamins, pigments)
Fatty Acids
Carboxylic acids with hydrocarbon chains containing 4 to 36 carbons
Saturated Fatty Acids
No double bonds between carbons in the chain
Monosaturated Fatty Acids
1 double bond between carbons in the chain
Polysaturated Fatty Acids
More than 1 double bond between carbons in the chain
Fuel Storage: Fatty Acids
Fatty acids carry more energy per carbon because they are more reduced and carry less water as opposed to Polysaccharides
Glucose vs. Fats
Glucose and Glycogen: fullfil short-term energy requirements, quick delivery
Fats: fullfil long-term energy needs, slow delivery, good storage
Fatty Acid Transport into Mitochondria
Triacylglycerides (TAGs) are degraded into Glycerol and Fatty Acids and transported into the Mitochondria for β oxidation via acyl-carnitine/carnitine transporter
Acyl-carnitine/Carnitine Transporter
Fatty Acyl-CoA + Carnitine -> Fatty Acyl-Carnitine –> Carnitine + Fatty Acyl-CoA
Fatty Acid Oxidation
Stage 1: oxidative conversion of 2 carbon units into Acetyl-CoA via β oxidation, generating NADH and FADH2
Stage 2: Oxidation of Acetyl-CoA in Citric Acid Cycle generating NADH and FADH2
Stage 3: Generation of ATP from NADH and FADH2 via Electron Transport Chain
The β-Oxidation Pathway
Each pass removes one acetyl moiety in the fomr of Acetyl-CoA
Fatty Acid Oxidation
Performed by a single multi-function, multi-subunit protein (Hetero-octamer). ATP total yield = 108ATP
Hetero-Octamer
Built up of:
- 4 Alpha subunits (responsible for binding to membrane)
- 4 Beta subunits
Oxidation of Unsaturated Fatty Acids: Isomerase
Converts Cis double bonds starting at Carbon 3 to trans double bonds
Oxidation of Unsaturated Fatty Acids: Reductase
Reduces Cis double bonds not at Carbon 3
Ketone Bodies
When oxaloacetate is depleted, Acetyl-CoA is converted into Ketone Bodies. 3 forms exit the liver: Acetone, Acetoacetate, and β-hydroxybutyrate
Formation of Ketone Bodies: Part 1
3 Acetyl CoA -> HMG-CoA
Formation of Ketone Bodies: Part 2
HMG-CoA -> 3 Ketones
Catabolism/Anabolism of Fatty Acids
Catabolism (Beta Oxidation)
- produces Acety-CoA, reducing power (NADH, FADH2)
- takes place in the mitochondria
Anabolism
- requires Acetyl-CoA, Malonyl-CoA and reducing power (NADPH)
- takes place in Cytosol in animals
Fatty Acid Synthesis
Overall goal: attach acetate unit (2-carbon) from malonyl-CoA to a growing chain (Palmitate) and then reduce it.
Fatty Acid Synthesis Steps
- Condensation of the growing chain with activated acetate
- Reduction of carbonyl to hydroxyl
- Dehydration of alcohol to trans-alkene
- Reduction of alkene to alkane
Fatty Acid Synthesis: Step 1
Malonyl-CoA Is Formed from Acetyl-CoA and Bicarbonate
- catalyzed by acetyl-CoA carboxylase (ACC)
Fatty Acid Synthesis: Step 2
Elongation of Fatty Acyl chain by 2 Carbons per step
- catalyzed by Fatty Acid Synthase (FAS)
Amino Acid Catabolism
- Recycled into new proteins
2. Oxidized for energy (removal of amino group in Urea cycle, entry into central catabolism (TCA cycle)
Excretory Forms of Nitrogen
- Ammonium
- Urea
- Uric Acid
Enzymatic Transaminations
Transfer of one amine to usually α-ketoglutarate results in synthesis of glutamate. Catalyzed by amino-transferases
The Glucose-Alanine Cycle
Works to remove lactate in bloodstream by converting it into Pyruvate and then converted into Alanine for transport to liver
The Urea Cycle: Initial Phase
- NH4+ from excess Glutamate converted to Carbomoyl Phosphate
The Urea Cycle: Following Phases
- Carbomoyl Phosphate condensed with Ornithine to produce Citrullene
- Citrullene combines with Aspartate (uses ATP) to form Argininosuccinate
- Argininosuccinate is cleaved to form Arginine
- Arginine is hydrolysed to regenerate Ornithine
- Process begins again
Ketogenic vs. Glucogenic AA’s
Ketogenic: can be converted to Ketone bodies
Glucogenic: can be converted to Glucose
End Products of Amino Acid Degredation
Can be converted to Acetyl-CoA (7), Pyruvate (6), α-ketoglutarate (5), Succinyl-CoA (4), Fumarate (2) and Oxaloacetate (2)
Biosynthesis of Amino Acids and Nucleotides
Transaminations and rearrangements using Pyridoxal Phosphate (PLP). Catalyzed by amidotransferases
Amino Acid Origins
Citric Acid Cycle: α-ketoglutarate, oxaloacetate
Glycolysis: pyruvate, 3-phosphoglycerate, phosphoenolpyruvate
Pentose Phosphate Pathway: ribose 5-phosphate, erythrose 4-phosphate
