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18 Cards in this Set

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Describe adipose tissue (TAG) lipolysis and the regulation of hormone sensitive lipase (HSL).
TAG is broken down to glycerol and NEFAs in white adipose tissue by hormone-sensitive lipase (HSL).

HSL is up-regulated by catecholamines (epi and norepi) which stimulate its phosphorylation.

It is down-regulated by insulin which enhances its dephospohorylation form.
Indicate mechanism of fatty acid transport to the tissues.
Both glycerol and NEFA diffuse out of the cell where the NEFA is attached to Albumin for transport to the tissues.
Describe fatty acid activation
A thioester bond is formed between the COOH group of a NEFA and the thiol group of Coenzyme A (CoA-SH)

Thiokinase (acyl-CoA synthetase) is the enzyme and is endergonic and so linked to ATP - ADP + Pi.
Describe the carnitine shuttle mechanism
1. in the Outer Membrane - Acyl-CoA + carnitine → acyl-carnitine by CPT-1 (carnitine palmitoyl transferase I)
2. Acyl-carnitine passed through porin channel protein to intermembrane space.
3. Inner Membrane bound acyl-carnitine translocase passes acyl-carnitine into the matrix with the enzyme CPT II (carnitine palmitoyl transferase II)
4. CoA is converted to Acyl-CoA in the matrix
5. Carnitine is passed through the membrane by the same translocase.
Explain the biochemical consequences of defects in transport of fatty acids (carnitine deficiency and CPT deficiency)
CPT 1 Deficiency - affects liver, reduced FA oxidation, hypoketotic, hypoglycaemic, probably lethal

CPT II Deficiency - affects skeletal/cardiac muscle, cardiomyopathy, muscle pain, cramps (after exercise), muscle necrosis (myoglobinuria)

Acyl-carnitine translocase deficiency - muscle weakness, hypoglycaemic, hyperammonaemic & cardiomyopathy. Fatal in infancy.

Plasma membrane (OCN-2) carnitine transporter deficiency (in muscle) - Myopathic Carnitine Deficiency (Systemic carnitine deficiency) - defective sodium-dependent transport. Low intracellular carnitine levels, compromised acyl-oxidations in tissues, mild cramps to severe weakness.

Secondary carnitine deficiency - metabolic, not inheritable, defects in beta-oxidation pathway lead to acyl-carnitine accumulation which are excreted from the kidneys.
List the reactions of the mitochondrial beta-0xidation pathway (not substrate names)
Fatty acyl CoA
1. Acyl CoA Dehydrogenase (oxidation)
2. Enol CoA hydratase (hydration)
3. 3-Hydroxyacyl CoA dehydrogenase (oxidation)
4. beta-Ketoacyl-CoA thiolase (cleavage requiring 2 CoA)
Fatty acyl CoA and Acetyl CoA
Outline the energetics of beta-oxidation
1. Divide the number of carbons in half
2. That is the number of Acetyl-CoAs made
3. Subtract one for the number of FADH2 and NADH
4. Each Acetyl CoA = 12 ATP, FADH2 = 2 ATP, NADH = 3 ATP
Indicate the end products of oxidation of odd chain fatty acids
The final acyl group is a 3-C propionyl-CoA. It is converted to succinyl-CoA.
indicate the biochemical defect in Refsum's disease
Refsum's disease (phytanic acidstorage syndrome) is the result of the inability to metabolise phytanic acid and its aggregation in tissue and blood.
Cause - Autosomal recessive
Symptoms - progressi ve neurolgical difficulties (tremors, unsteady gain and poor night vision)
Pathology - segmental demyelination of peripheral nerves with hypertrophy second to Schwann cell proliferation
Treatment - strict dietary management avoiding green vegetables.
Distinguish between medium-chain acyl-CoA dehydrogenase deficiency and Jamaican vomiting sickness based on the pathogenetic mechanism and biochemical alterations
Med-Chain Acyl-CoA dehydrogenase deficiency (MCAD) is a congenital deficiency where this enzyme is missing.

Jamaican Vomiting Sickness is a result of the toxin in unripe akee fruit. The toxin is an irreversible inhibitor of short and medium chain acyl-CoA dehydrogenases.
Outline peroxisomal alpha- and beta-oxidation
Peroxisomal alpha-oxidation reduces fatty acids one carbon at a time.
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Peroxisomal beta-oxidation specifically oxidized VLCFAs.
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Discuss Zellweger's syndrome as a disorder of peroxisomes
Defective peroxins (proteins for peroxisomal biogenesis) lead to an absence of peroxisomes. VLCFAs accumulate in plasma and tissues and become toxic in the CNS.
Describe the pathway of hepatic ketogenesis and list the ketone bodies
Acetone - Acetoacetate - β-hydroxybutyrate

1. Ketothiolase condenses 2 acetyl-CoAs into Acetoacetyl-CoA
2. It condenses with another acetyl-CoA to form β-hydroxy-β-methylglutaryl-CoA (HMG-CoA)
3. HMG-CoA Lyase removes an acetyl-CoA forming Acetoacetate.
4. Acetoacetate may undergo spontaneous decarboxylation in the blood to form acetone.
Explain ketone body utilization in peripheral tissues
Acetoacetate can be reconverted to acetyl-CoA once you are out of the liver. It is catalyzed by syccinyl-CoA:acetoacetate-CoA (thiophorase). The brain uses this during periods of starvation as ketonebodies can pass the blood-brain barrier.
Prepare a concept map indicating the steps involved in the generation of ketosis in starvation and uncontrolled type 1 diabetes mellitus
X
Correlate laboratory data in ketoacidosis (laboratory data in blood and urine) to the clinical signs in the patient; including hyperventilation
X
Outline oxidation of branched chain fatty acids
1. Peroxisomal oxidation removes single carbons from branched fatty acids until they are unbranched.
2. The fatty acid is passed to the beta-oxidation pathway (peroxisomal or not)