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26 Cards in this Set
- Front
- Back
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Before FA catabolism occurs it has to be activated... where does this occur and how?
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in cytosol acyl CoA synthetase synthesizes thioester linkage to coenzyme A and produces fatty acyl CoA
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The transfer of the fatty acid unit involves carnitine palmitoyl transferase I (CPT I or CoA-carnitine acyltransferase I), What negatively regulates the CPTI?
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manolyl CoA
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a. Regulation of B-oxidation is primarily by?
b. Availability of fatty acids can be stimulated/inhibited by? |
a. fatty acids, oxidized enzymes (NAD and FADH)
b. stimulated by glucagon and epi inhibited by insulin |
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What inhibits step 4 of B-oxidation (ketothiolase)?
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high mitochondrial acetyla CoA
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what is the purpose of the uncoupling mechanism of brown fat?
what protein is responsible for this mechanism? |
it generates excess heat, which helps to keep newborns warm
thermogenin |
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What are two other types (routes) of FA oxidation
Where do they occur? What is uniqueness of these oxidation types? |
- alpha (a) peroxisomal and detected in brain tissue does not require CoA intermediates or high energy phosphates
- omega (w) microsomal involving enzymes P450 in the ER - neither is feedback regulated |
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What is the characteristic features of a carnitine metabolism deficiency? MC type?
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hypoketotic hypoglycemia which can lead to hepato-encephalopathy and can be lethal
- also causes muscle weakness and hypotonia MC is MCAD (Medium-chain acyl CoA dehydrogenase) |
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A CPT-I deficit affects primarily liver and leads to?
What meds inhibit CPT-1? |
reduced FA oxidation
ketogenesis elevted plasma free carnitine Meds- oral hypoglycemic agents inhibit CPT-1 |
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Acyl CoA dehydrogenase deficiency leads to what?
Named? |
increased dicarboxylic acids, increased glucose and ketones
- due to impaired B-oxidation - Medium chain acyl CoA dehydrogenase (MC genetic disorder) |
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Role of peroxisomes?
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long chain reduction one carbon at a time to prepare for B-oxidation
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What enzyme is missing/deficiency in Refsum disease?
Symptoms? Tx? |
phytanoyl CoA hydroxylase can not create pristanic acid
-Symptoms • Retinitis pigmentosa • Cerebellar ataxia • Chronic polyneuropathy - Treatment- Low-phytanic acid diet provides marked improvement |
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•Symptoms
• Retinitis pigmentosa • Cerebellar ataxia • Chronic polyneuropathy dx? |
Refsum disease
defect in single peroxisomal enzyme phytanoyl CoA hydroxylase |
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Name the three main ketone bodies?
Where does this occur? |
liver mitochondrial matrix
• Acetoacetate • b-hydroxybutyrate • Acetone |
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Rate determining enzyme in metabolic processes of ketogenesis
When the products from the rate limiting enzyme is made and leaves the mitochdria.... what does it leave as and what does it eventually make? |
HMG-CoA synthase
- leaves as mevalonate the precursor for cholesterol |
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Why can't ketone bodies be catabolized in liver?
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succinyl CoA acetoacetate CoA transferase is not in the liver
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How does an activated fatty acid get shuttled into where it will be beta oxidized?
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Carnitine shuttle-
1. Acyl CoA is conjugated to carnitine by CPT1 (carnitine palmitoyl transferase I) located on the outer mitochondrial membrane 2. Acylcarnitine is shuttled inside by a carnitine acylcarnitine translocase 3. A reversal exchange takes place through CPTII and carnitine comes off and we are left with Fatty acyl CoA ready for oxidation :) |
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Describe the products and steps of one round of B-oxidation?
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1 NADH, 1 FADH2, 1 acetyle CoA
Step 1: Acyl CoA becomes enoyl CoA by acyl CoA dehydrogenase (makes FADH2) 2. enoyl CoA hydrase makes L-3hyroxyacyl CoA 3. L-3-hydroxyacyl CoA dehydrogenase makes 3-ketoacyl CoA and NADH 4. 3-ketothiolase cleaves product to acetyl CoA and an acyl CoA (fatty acid now 2 C's shorter) |
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What are the basic summary steps of what goes on in B-oxidation in one cycle?
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1. First oxidation
2. hydration 3. second oxidation 4. thiolysis |
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How much ATP and show how you calculate it from B-oxidation of Palmitate (16-C)
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7 repetitions of the B-oxidation spiral)
7x 4= 28 TCA- 8 acetyl CoA= 8 x 10= 80 108-2 = 106 |
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What is the difference between b-oxidation of for unsaturated fatty acids?
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same but 2 additional enzymes... an isomerase and a reductase
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Where might alpha oxidation be used or what might it be used on...
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- a oxidation occurs in the peroxisomes useis phytanoyl CoA hydroxylase
long chain fatty acids greater than 20 before they go into the mitochondria |
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What is the key enzyme used in alpha oxidation?
What does it convert? What if there is def? (symptoms?) |
phytanoyl CoA hydroxylase which converts phytanic acid to pristanic
- deficeincy causes Refsum disease symptoms- retinitis pigmentosa, cerebellar ataxia, chronic polyneuropathy |
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This syndrome is caused by a lack of reduction of peroxisomes, characterized by accumulation of long chain fatty acids and branched chain, pristanic acids in plasma and tissues..
Results in? What population is MC? |
Zellweger syndrome
- infants usually results in death during 6-12 months |
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What happens when there is a deficiency of acyl CoA dehydrogenase?
Called what? Inheritance? (characterized by?) |
leads to impaired B-oxidation
- called medium chain acyl CoA dehydrogenase (MCAD) deficiency (MC genetic disorder) - AR disease which characterized by hypoketotic hypoglycemia |
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Describe the three main levels of Regulation of Ketogenesis?
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1. Substrate- level regulation- more Free FA's will increase ketogenesis in liver
2. Carbohydrate utilization- if low carb usage or deficit in usage, there increases ketogenesis 3. Gluconeogenesis- ketone bodies are produced during this time while deriving energy from B-oxidation |
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Where are ketones broken down?
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NOT IN THE LIVER FUCK FACE! (due to lack of sucinyl CoA Acetoacetate CoA transferase)
- heart and skeletal muscle and secreted in the urine as salts |
