8 - Lipids 2

Question 1

What are the classes of complex lipids and where are they found?

Answer 1

Question 2

What is the clinical significance of glycerophospholipids? What happens when their function is disrupted?

Answer 2

Question 3

What is the clinical significance of Sphingolipids? What happens when their function is disrupted?

Answer 3

Question 4

Answer 4

Question 5

Answer 5

Question 6

Answer 6

Question 7

Answer 7

Question 8

What is an eicosanoid?

Answer 8

Question 9

How are eicosanoids synthesized?

Answer 9

Arachidonic acid and Cyclooxygenase pathway

Question 10

Where can the function of eicosanoids be seen in the body?

Answer 10

Question 11

What are the states in fatty acid and triacyglycerol metabolism?

Answer 11

Fed State, Fasted state, Prolonged fasted state

Question 12

What are the diseases associated with fatty acid and triacylglycerol catabolism?

Answer 12

Question 13

How is lipolysis hormonally regulated?

Answer 13

Question 14

Give an overview of fatty acid and triacylglycerol catabolism?

Answer 14

• Oxidative process (mitochondria or peroxisomes)
• The catabolism of fatty acids, via β-oxidation
• Release of two carbons/cycle
• Main working-products: Acetyl-CoA, FADH2, NADH
  Importance of β-oxidation:
  During overnight fasting, fatty acids are a major fuel source for cardiac muscle, skeletal muscle, and liver.
  Brain has a limited capacity to use fatty acids for fuel: the conversion of FAs to ketone bodies during β-oxidation provides fuel for the brain during prolonged fasting.

Question 15

How are fatty acids transported into cells for catabolism?

Answer 15

Question 16

How are fatty acids “activated” or primed for catabolism? Why is activation important?

Answer 16

Fatty acid activation allows entering mitochondria
* Fatty acyl-CoA diffusely pass via outer membrane
(Porins opening)

Question 17

How are fatty acids transported to the matrix of the mitochondria for catabolism? What is the disease associated with this mechanism?

Answer 17

Carnitine can be obtained from the diet or synthesized from the amino acid lysine and methionine in liver and kidneys * Carnitine deficiency
* Primary Carnitine deficiency (PCD)
* Deficiency in the organic carnitine transporter novel type II (OCTN2).
Encoded by Solute carrier family 22 member 5 (SLC22A5)
* Muscle weakness
* Treatment: Life-long supplementation of oral L-carnitine (100 to 200 mg/kg
daily)

Question 18

How is β-oxidation performed when fatty acids reach the mitochondrial matrix?

Answer 18

Question 19

How does the length of the fatty acid chain affect its catabolism?

Answer 19

Medium-chain FAs
* Superior solubility compared to long-chain fatty acids
* Enter the mitochondrion via diffusion
* Medium-chain enzymes cleaves two-carbons/cycle
Odd-Chain FAs
* Two-carbons cleavage occurs until five-carbon fatty acyl-CoA is formed
* Thiolase: forms Acetyl-CoA + propionyl-CoA, propionyl-CoA is converted to succinyl-CoA (Moves to TCA Cycle)
Very-long chain FAs
* Cannot enter mitochondria
* Processed in peroxisomes
* β- and α-oxidation pathway

Question 20

What diseases are associated with fatty acid metabolism?

Answer 20

Zellweger syndrome
* Peroxisomal dysfunction
* Inability to import very-long-chain Fatty acids
* Multiorgan disorder
* High mortality (6 months of age)
* Hepatic, cerebral and renal degeneration
* Hypotonia
* No Cure

Question 21

When/why are ketone bodies formed?

Answer 21

Question 22

How are ketone bodies formed?

Answer 22