Lipid and amino acid metabolism Flashcards
what happens to amino acids that are not used for protein synthesis
where is the major site of this
they are degraded
liver
what toxic substance is made from the breakdown of some amino acid side chains
how is it safely excreted
ammonia and ammonium ions
urea cycle
what can the carbon skeleton of ketogenic amino acids be broken down to
acetyl-CoA or acetoacetyl-CoA
ketone bodies or fatty acids
what can the carbon skeleton of glycogenic amino acids be broken down to
pyruvate or TCA intermediates
converted to phosphoenolpyruvate then into glucose
what can result from fat deficiencies
membrane disorders
increased skin permeability
mitochondrial damage
deficiencies of fat-soluble vitamins
what is the main energy storage form in adipose tissue
what is its structure
triglycerides = triacylglycerols
glycerol head and 3 fatty acid chains
what are the main products of fat digestion
glycerol
fatty acids
monoglycerides
what happens to different lengths of fatty acids when they are broken down from triglycerides
short and medium-length FAs enter portal blood
longer chains and monoglycerides are re-synthesised to triglycerides
what are chylomicrons
small fat packages coated with protein phospholipid and cholesterol
transported via lymph and blood
what initially starts the lipolysis of stored fat
hormone-sensitive lipases
before fatty acids can be oxidised they have to be converted to what?
where does this occur
CoA derivatives
cytosol
how does acyl-CoA get transported to the mitochondrial matrix for further oxidation?
the carnitine shuttle
translocase facilitates the antiport of acyl-carnitine into the mitochondrion and carnitine out
explain beta-oxidation of fatty acids
A 4-step cycle of reactions in the mitochondrial matrix
each producing:
1 acetyl-CoA
1 FADH2
1 NADH + H+
1 fatty acyl-CoA shortened by 2 carbons (unless last one)
how to calculate the yield of beta-oxidation of fatty acids
the cycle is repeated once for every two carbons - one time
creating:
- 1 NADH + H+ and FADH2 for every cycle
- half as many acetyl-CoA as the number of carbons on the acyl group
- 1 GTP, 1 FADH2 and 3 NADH from TCA of acetyl-CoA
- p/o ratio of ATP for NADH and FADH2 - 2 from activation step
when does lipogenesis occur
when there is excess energy intake
