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56 Cards in this Set
- Front
- Back
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The bodies major store of energy is in the form of?
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Triglycerides which are found mainly in adipocytes (fat cells)
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What about TG's makes them a good energy storage form?
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Many of their C-C bonds in their FA's are highly reduced and have many e-'s for electron transport and eventual production of ATP
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Are FA's hydrophobic or hydrophilic?
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Hydrophobic, and they contain very little water. They yeild 9 kcal of energy per gram.
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How many kcals/g do the following contain?
FAT PROTEIN CHO (carbohydrate) EToH |
9 kcal/g (FAT)
4 kcal/g (PROTEIN) 4 kcal/g (carbs) 7 kcal/g EToH |
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What action starts the process of liberating energy stores from adipocytes?
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Epinephrin binding receptors on the surface of adipocytes and effecting a cAMP signal cascade which stimulates Hormone-Sensitive Lipase to clip a FA tails one at a time off of a TG's within the adipocytes.
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What is hormone sensitive lipase and what stimulates its activity?
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Hormone sensitive lipase is a hormone found within adipocytes which is activated by protein kinase activation by cAMP.
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What is the result of low insulin on TG's?
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Low insulin levels stimulates an increase in cAMP activity which leads to TG catabolism.
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What do lipases produce?
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Glycerol + (2) FA's
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What inactivates hormone sensitive lipase activity?
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Phosphatase
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Is glycerol kinase found in adipocytes?
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No. So the glycerol is sent to the liver for process.
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In the liver what does glycerol kinase do?
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Converts glycerol to glycerol-po4 which can become DHAP for glycolysis or gluconeogenesis (equals bad times). Or the Gly-po4 can be used for TG synthesis
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What is the fate of the FFA's after they are liberated from TG's by hormone sensitive lipase?
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The FFA's diffuse through the adipocyte membrane and are bound by albumin in the blood and can diffuse into cells which need them for energy production
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Which 3 tissues DO NOT use FA's at all?
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1. Brain
2. RBC's 3. Adrenal Medulla |
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By what process do we use FFA's for energy production?
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Beta Oxidation of FFA's
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What two tissues use FFA's most?
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Skeletal muscle loves FFA's, as well as the liver.
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So FFA's diffuse into the cytosol of cells which need them, what process traps them in the cytosol?
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Conversion to FA CoA via Fatty acyl CoA synthase, which uses a PPi (equiv. of 2 ATP's)
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Where does Beta Oxidation actually take place?
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Mitochondrial matrix
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How do FA-CoA's get from cell cytosol to mitochondrial matrix?
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They are transferred using Carnitine. FA-CoA is bound to carnitine in the inner mitochondrial membrane becoming acyl-carnitine, then another CoA is added via carnitine acyl transferase yeilding Acyl CoA in the mitochondrial matrix.
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The process of getting FA-CoA into the mitochondrial matrix is regulated by what enzyme?
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It is inhibited by Malonyl CoA found in the cytosol. Malonyl CoA is a substrate for FA synthesis so it wouldn't make sense to be breaking it down. It inhibits the carnitine acyltransferase.
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What regarding FA CoA length has been implicated is SIDS cases?
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Shortage of medium-length FA CoA
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What is the role of carnitine in the inner mitochondrial membrane?
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It is an acyl carrier protein, carries the acyl group across the membrane.
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When does Beta Oxidation begin?
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Once the Acyl CoA has entered the mitochondrial matrix.
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In Beta Oxidation Acyl CoA is converted to Trans delta-2 enoyl CoA by which enzyme?
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Acyl CoA DH, and there is an energy yeild of (1) FADH2.
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Trans delta-2 enoyl CoA is converted to 3-HA CoA by which enzyme?
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Enoyl CoA Hydratase
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What enzyme converts 3-Hydroxyacyl CoA to Ketoacyl CoA?
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L-3-Hydroxyacyl CoA DH, 2nd indirect energy harvest occurs here in the form of NADH.
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What enzyme converts Ketoacyl CoA to Acyl (n-2) CoA + (1) AcCoa?
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Beta-Keto Thiolase, with the addition of CoA
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What substrates exist in the cycle of Beta Oxidation?
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Acyl CoA
Trans delta 2 enoyl CoA 3 Hydroxyacyl CoA KetoAcyl CoA Acyl (n--2) + (1) AcCoA |
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Energy yield from Beta Oxidation per round?
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Using:
Acyl-CoA, FAD, NAD+, H2O, CoA Getting: Acyl n-2 CoA FADH2 (2 ATP) NADH (3 ATP) AcCoa (12 ATP) Total: 17 ATP per round. |
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Beta Oxidation of (1) palmitate yields?
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(7 cycles, ([#carbons/2)]-1), 7 FADH2 (14 ATP), 7 NADH (21 ATP), 8 CoA (96 ATP). Total=131 ATP
BUT cost (2) ~p so total yield is 129 ATP A TG with 3 palmitates is worth 129*3=409 ATP |
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In beta oxidation of an odd numbered FA or in case of an unsaturation other enzymes are needed. Which are they?
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Isomerase (converts cis to trans)
Epimerase (shifts hydroxyl group |
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What happens to the energy yield in the case of an unsaturated FA or odd chain length?
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Reduced by 2 ATP/C=C bond. This is because the AcylCoA Dehydratase rxn is skipped (losing an FAD going to FADH2)
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In beta oxidation of an odd chain length FA what happens in the last step that is different from even chain length beta oxidation?
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The last cycle will yield (1) AcCoA and (1) Propionyl CoA which is 3 C's rather than two (2) Carbon AcCoA
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What happens to Propionyl CoA after Beta Oxidation?
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Converted by Propionyl CoA Carboxylase to Methylmalonyl CoA using ATP and gainin CO2. This is then converted to Succinyl CoA by methylmalonyl CoA mutase and is sent on to be used by the TCA cycle.
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What important cofactor is required for converting propionyl CoA?
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Vitamin B12 is needed as a cofactor for methylmalonyl CoA mutase.
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Attributes of FA synthesis after a meal.
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-Stim by insulin, inhib by glucagon
-Happening in liver -Occuring in the cytosol -Citrate is the trans. carrier -Holder is ACP -Product is Palmitate -Activated by Citrate -Inhibited by FA CoA |
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Attributes of FA synthesis during starvation.
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-Low insulin
-High glucagon -Occuring in muscle/liver -Occuring in the mitochond. -Transport carrier=Carnitine -Holder is CoA -Product is AcCoA -No activator on list -Inhibited by Malonyl CoA |
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How does the liver convert AcCoA into Ketone bodies?
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There are liver enzymes that convert them to:
Acetoacetate Beta-hydroxybutyrate Acetone (non-metabolizable and toxic) |
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What are the three ketone bodies produced by the liver from AcCoA?
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Acetoacetate
Beta-hydroxybutyrate Acetone |
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What advantage do ketone bodies have over FA's in the blood?
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Ketone bodies are water soluble so they can float freely and unbound. Skeletal muscles and reanal cells can convert acetoacetate and beta-hydroxybutyrate back into AcCoA.
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Can liver cells use the ketone bodies they produce?
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No, they cannot.
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During what situation are ketone bodies being made?
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During periods of starvation. They are also being produced in cases of untreated diabetes mellitus where the body think its in a prolonged fast due to insulin insensitivity where the cells are starving for glucose which they aren't recieving.
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What is the rate limiting enzyme for keton body synthesis in the liver?
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HMG-CoA Synthase, requires acetyl CoA to be introduced to AcetoAcetyl CoA (Whicc was obtained from combining (2) acetyl CoA units via Thiolase)
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What is the product of HMG-CoA synthase?
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Hydroxymethylglutaryl CoA ("HMG-CoA") which is a 6 C molecule
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What is the function of HMG-CoA lyase?
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Removes an AcCoA from HMG-CoA yielding Acetoacetate (a 4 C structure)
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What are the fates of acetoacetate in regards to ketone bodies?
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Acetoacetate, a 4 C ketone body can be converted to 3-OH-Butyrate (beta-oh-butyrate) via 3-OH butyrate DHase. Or, can spontaneously eject a CO2 and become acetone which is toxic to the blood and is exhaled in the lungs.
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What can ketosis be mistaken for in certain circumstances?
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Intoxication, breath will smell like alcohol.
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What happens to Acetoacetate and or 3-OH-Butyrate (Beta-OH-Butyrate)?
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Enters circulation and is taken up by tissues such as skeletal muscle.
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What is the ATP loss when converting acetoacetate to beta-oh-butyrate?
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Uses an NADH so we are essentially tearing up a check for 3 ATP, this process is very generous.
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In muscle tissue what is the ultimate fate of Beta-OH-Butyrate?
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It is converted to (2) AcCoA which then enter the TCA cycle.
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Why can't the liver use ketone bodies?
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It lacks the enzyme thiophorase
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What is the result of elevated levels of the ketone bodies acetoacetate and Beta-OH-butyrate?
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They are both acids so the physiologic result is called Acidosis, low blood pH.
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What is ketonemia?
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High blood [ketone]
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What is ketonuria?
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High uring [keton]
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What enzyme converts Beta-OH-butyrate to Acetoacetate?
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Beta-OH-butyrate DH, energy yield of (1) NADH
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What is the function of Thiophorase?
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Converts acetoacetate to Acetoacetyl CoA (this is through the conversion of succinyl CoA to succinate in the TCA)
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What enzyme cleaves Acetoacetyl CoA?
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Thiolase, with the addition of (1) CoA needed to yield (2) AcCoA
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