Topic 7: Energy Production - Lipids Flashcards
what is the structure of lipids
diverse
insoluble in water - hydrophobic
C, H, O and P and N
more reduced than carbs - release more energy when oxidised, so requires more O2
what are the classes of lipids
- fatty acid derivatives: fatty acid - fuel molecules. triacylglercrides - fat in adipose, phopsholipids - membranes and plasma lipoproteins, eicosanoids - local mediators
- hydroxy-methyl-glutaric acid derivatives (6C): ketone bodies - water soluble fuel molecules, cholesterol - membranes and steroid hormone, cholesterol esters - cholesterol storage, bile acids and salts - lipid digestion
- vitamins - A, D, E and K
how is a healthy man’s energy store distributed
triacylglerols, glycogen, muscle protein
more triacylglycerol in overweight (high energy content - lots to lose)
how much energy is needed
10-11000KJ per day
what are triacylglycerols
the fats that are storage fats in adipose tissue or fatty tissue
glycerol backbone (3C) attached to fatty acid side chain
space filling molecules
how are tiacylglycerols synthesised
glycerol and 3 fatty acids by esterification (removal of water)
opposite is lipolysis - break down
how are triacylglyerols stored
hydrophobic - stored in anhydrous form
in specialised tissue - adipose
when are triacylglyerols used
in prolonged exercise, starvation, during pregnancy
storage/mobilisation is under hormonal control
what tissues are imvolved in triglyceride metabolsim
GI tract - to glycerol and fatty acids
glycerol enters blood to liver - metabolised
fatty acids packed into chylomicrons in blood, released into circulation via lymphatics, which are transported to adipose tissue where stored. can be broken down into fatty acids for muscles for energy use
stage 1 of triglyceride metaboism
extracellular
pancreatic lipases cleave lipids into fatty acids and glycerol
then recombined into small tissue and transported as TAG by lipoproteins (chylomicrons)
if consumer tissue - fatty acid oxidation = energy (require mitochondria which brain and RBC dont have)
if adipose tissue -when in excess and stored as TAG - can be transported when mobilised on albumin to consumer tissues
how are triglycerides mobilised
hormone sensitive lipase
activated by if glucagon/adrenaline - increase
inhibited if insulin if energy levels high - decrease (so inhibit breakdown, so stored)
how are fatty acids made to be stored in adipose tissue
when lots of glucose - lots of glycerol-1-p
triglycerides - fatty acids and glycerol
fatty acids converted fatty acyl coA
then combined with glycerol-1-p to form triglyceride (to store)
how and why is fatty acid not stored in adipose
less glucose - less glycerol - 1 -phosphate
so re synthesis of triglyceride inhibited - levels of fatty acid build up - released into circulation - picked up by albumin - consumer tissues (less glucose - fatty acid as alternative fuel)
what is the formulae for fatty acids
CH3(CH2)nCOOH
fatty acids can be
unsaturated or saturated
amiphipathic - both hydrophobic and philic
