Fatty acid degradation

9 important questions on Fatty acid degradation

What are the 4 functions of fatty acid?

  • Building blocks
    • phospholipids and glycolipids constituents of membrane
  • Targeting
    • bind to protein directing them to designated location in membrane
  • Messengers
    • serve as hormones and intracellular messenger molecules
  • Energy
    • stored as triacyglycerols (TAG)

What is the structure of triglycerides? Where are they stored?

Triacyglycerols
  • glycerol is the hook where the fatty acid are attached to
  • stored in fat cells/lipid droplets, called adipocytes

How are triglycerides (fat) taken up from the food?

Triglycerides (TAG) is broken down by lipase (from pancreas) forming 2 fatty acids and 1 monoacylglycerols. Both molecules can go through the intestine wall and form triglcyerides again. The tirglyceries and other lipids/protein form chylomicrons (lipoprotein) goes to the lymphatic to the blood, Lipases takes the fatty acids up and puts it in the adipose tissue.
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What are the steps when fat is being burned due to fasting/hunger state?

  1. Mobilization
  2. Activation and transport
  3. Degradation

How are long fatty acids (>C20) degraded?

Peroxisome
  • first step  of fatty acid degradation in peroxisome, which is catalyzed by a FAD containing dehydrogenase, the electrons are directly transferred to molecular oxygen to yield hydrogen peroxide H2O2
    • electrons are lost and will produce less ATP in the later TCA cycle
  • H2O2 is degraded by catalase in H2O and O2
  • The remaining of the reaction are the same
  • peroxisome have no TCA cycle, the formed acetyl-CoA is transported to mitochondria for degradation to CO2 and H2O

What happens when a fatty acid degradation occurs with an odd number of carbon atoms?

Last step of thyolysis step results into propionyl-CoA (C3-CoA) and acetyl-CoA (C2-CoA).
  • Propionyl-CoA is converted into succinyl-CoA (C4-CoA), which is an intermediate of the TCA cycle and can be converted into oxaloacetate (C4) to make glucose
  • Propionyl-CoA carboxylase

What happens when a fatty acid degradation occurs which is unsaturated?

It requires additional enzymes

for odd carbon atom
  • isomerase: shifts the position of the double bond from an odd carbon atom to a even carbon atom.


for even carbon atom
  • isomerase
  • reductase

Each unsaturated fatty acid can be completely degraded with only 2 additional enzyme

What is the use of ketone bodies?

Keton bodies are provided by the liver during fasting and starvation (glucagon, promotes triglycerol breakdown). The fatty acid are converted into ketone bodies that can be used in other tissues (heart muscle cell, skeletal muscle and brain) as a source of energy via blood transportation. The ketone body go into the mitochondria of these tissues to make ATP.

How are ketone bodies formed and where?

  • Only in liver
  • are formed from acetyl-CoA when fat breakdown predominates used as a source of energy in the body
  • Acetoacetate(C4) can be converted to acetyl-CoA and is an important fuel in some tissues (heart muscle, skeletal muscle, brain)
    • 2 acetyl groups attached to each other
    • can be converted to acetyl-CoA

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