QOTD:

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QOTD "The important thing in science is not so
much to obtain new facts as to discover new
ways of thinking about them." - Sir William
Bragg
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Fatty acid biosynthesis and breakdown occur by
different pathways. Use different enzymes. Occur
in different parts of the cell. Breakdown
Mitochondrial Synthesis cytosolic
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Fatty acids are elongated by other systems after
palmitate (16C). Some fatty acids are
de-saturated (oxidised) to put double bonds into
the structure . BUT only upto C9
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Figure 25-28 A comparison of fatty acid b
oxidation and fatty acid biosynthesis.
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n ( x,y..)
1
2
5
8
18
C-C-C-C-C-C-C-C-C-CC-C-CC-C-C-C-COOH
Animals cannot put double bonds in this part of
the molecule, plants can!
Essential fatty acids Linoleate 182(?9,12)
Arachidonate 204(?5,8,11,12)
3. Synthesis of fatty acids
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Regulation

• Primarily at AcetylCoA Carboxylase
• First committed step in synthetic pathway
• Citrate activates AcetylCoA carboxylase
• Palmitate inhibits AcetylCoACarboxylase
• Malonyl CoA inhibits mitochondrial transport of
  FACoA
• cAMP dependent phosphorylation inhibits
  AcetylCoACarboxylase and activates lipase in
  adipocytes.
• Insulin dependent dephosphorylation activates
  enzyme

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Fig 25-40 Sites of regulation of fatty acid
metabolism.
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Functions of fatty acids

• As constituent of triglycerides
• represent the major store of energy in
  triglyceride we saw how fatty acids (e.g. from
  diet or from storage as triglyceride) were
  oxidised to provide energy (ß-oxidation).

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Function of fatty acids

• As constituent of phospholipids and glycolypids
• Cell and organelle membranes
• Nerve Cell membranes
• Large number of disorders associated with
  glycolipid disorders
• Precursor of Eicosanoids (Prostaglandins are one
  type).