LECTURE 5 (Lipid degradation) Flashcards
What are the properties of Fatty acids in the body?
- Stored in adipose tissue (as TAGs)
- Serve as the body’s major fuel storage reserve
- Yield from complete oxidation of Fatty acids to CO2 and H2O is 9 kcal/g (higher than in proteins + carbohydrates)
What is Hormone-sensitive lipase?
An enzyme that removes fatty acid from TAG in adipocytes
ACTIVATION: by glucagon and epinephrine
What happens when Fatty acids are released from TAG?
Free fatty acids move through the cell membrane of adipocyte -> Bind to plasma ALBUMIN -> Transported to tissues -> Oxidised for energy
What happens to Glycerol released during TAG degradation?
It cannot be metabolised by adipocytes because they lack GLYCEROL KINASE -> Glycerol is transported through the blood to the liver where it can be phosphorylated -> Glycerol phosphate can be used to form TAG in liver or converted to DHAP
Why is Glycerol easily transported to liver?
Glycerol is water-soluble
Which processes are Facilitated by Insulin?
- Glucose entering White adipose tissue via GLUT 4
- Lipogenesis (conversion into fatty acids)
- Esterification of fatty acids into TAGs
Which process is inhibited by Insulin?
Breakdown of TAGs into Fatty acids
Describe Fatty acid breakdown
- Fatty acids transported via Albumin
- Taken up by tissues
What is Fatty acid breakdown not used by?
- RBC: glycolysis only (no mitochondria)
- BRAIN: glucose and ketones only
Why does brain metabolism not favour the burning of fatty acids to provide energy?
- ATP generation linked to B-oxidation of fatty acids demands more O2 than glucose -> enhance risk for neurons to become HYPOXIC
- B-oxidation of fatty acids generates SUPEROXIDE
[poor anti-oxidative defense in neurons -> severe oxidative stress] - Rate of ATP generation from Fatty acids to too slow
[cannot keep up with rapid, continuous neuronal firing]
What happens when Fatty acids reach tissues?
Fatty acids metabolised by BETA-OXIDATION mitochondrial pathway -> 2-carbon units are removed from FAs -> Produces acetyl-CoA, NADH and FADH2
What is the function of the Carnitine shuttle?
Transport long-chain fatty acyl CoA subunits across mitochondrial membranes from outside to inside
Describe the steps of Beta-oxidation of Fatty acids
1) Fatty acid conversion into FATTY ACYL-COA
2) Transport of fatty acyl-CoA from cytosol into inner mitochondria
3) Beta-oxidation
What is the Carnitine shuttle inhibited by?
MALONYL-COA
Explanation: When fatty acid synthesis occurs in cytosol -> newly make palmitate cannot be transferred into mitochondria and is degraded
What are the properties of Carnitine?
- Obtained from meat
- Synthesised from lysine and methionine
- De novo synthesis only in liver & kidney
- Skeletal muscle contains 97% of all carnitine in body