Fat metabolism (lecture 30) Flashcards
how are fats stored?
triglycerides
what are triglycerides made of?
glycerol and 3 fatty acids
an ester
how are triglycerides stored?
in white adipose tissue
provides thermal and electrical insulation
helps maintain body temp and cell structure
why is cholesterol bad for your health?
body cannot metabolise cholesterol
has to be recycled in the liver
why are fats a more efficient energy source compared to carbohydrates?
in glucose, carbons are partially oxidised
in palmitic acid, carbons are fully saturated
• releases more electrons
• can generate more ATP
• main storage of fatty acids
how do triglycerides vary?
in length and saturation
a double bond makes a ∆ fatty acid
• looses 2 hydrogens
• cis/trans isomerism
why are saturated fats bad?
straight molecules form very dense layers which are difficult to metabolise
double bonds form kinks which make it less dense when stored - makes it more accessible for enzymes
what is catabolism?
the breakdown of triglycerides (fatty acids)
what are the 3 stages of catabolism?
lipolysis
activation of fatty acids
oxidation of fatty acids - beta oxidation
what happens in lipolysis?
triglyceride broken up into glycerol and fatty acids
lipase breaks ester bond to release fatty acids
glycerol is recycled back to the liver
• glycerol converted to glycerol-3-phosphate by glycerol kinase
• this is oxidised to dihydroxyacetone phosphate by glycerol phosphate dehydrogenase
what happens in fatty acid activation?
fatty acids enter cytoplasm
activated by addition of CoA by acyl CoA synthetase
ATP to AMP in one step to release more energy
high affinity of pyrophosphorylase to the free phosphates keeps reaction going in 1 direction
mitochondria is impermeable to acyl CoA, how is this overcome?
acyl group is transported into the mitochondria as acyl-carnitine
translocate allows acyl carnitine to enter the mitochondria
carnitine is recycled back outside the mitochondria
what happens in beta oxidation?
activated fatty acid is oxidised by FAD
removes hydrogens to form FADH2 and introduces a double bond
water is added to the double bond
dehydrogenate to oxidise the beta carbon
cleavage - CoA can break the bond in beta oxidation spiral
what are the 4 stages if beta oxidation?
oxidation
hydration
oxidation
cleavage
what do you get from cleavage of a 16C molecule?
8 acetyl CoA
7 FADH2
7 NADH + H+
how many ATPs do you get out of 1 palmitic acid?
108
only 32 from glucose
what is the activation factor in beta oxidation?
CoA
what happens during starvation?
body swaps to fatty acid metabolism
glucagon is activated and gluconeogenesis starts
fatty acids cannot enter the CAC so fats are converted to ketone bodies
ketone bodies rise pH of the blood which is dangerous for diabetes
ketone properties
produced mainly in the liver
ketosis common in type 1 diabetes
distinctive fruity smell
ketone body formation
2 acetyl CoA joined together by thiolase to from acetoacetyl CoA
this can then form 3-hydroxy-3-methyl-glutaryl CoA
this can produce 3 ketone bodies
what are the 3 ketone bodies?
acetoacetate
acetone
D-3-hydroxy-butyrate
what is lipogenesis?
fatty acid synthesis
what are the 4 stages of lipogenesis?
condensation
reduction
dehydration
reduction
what is the committed step in lipogenesis?
formation of malonyl CoA
produced by adding CO2 to acetyl CoA by acetyl CoA carboxylase
what does lipogenesis lead to?
non alcoholic fatty liver disease (NAFLD)
- increases fat build up in the liver
- insulin resistance
- overweight and obesity
- type 2 diabetes
what is the activation factor in lipogenesis?
acyl carrier protein (ACP)
what is the key enzyme in controlling fatty acid synthesis?
acetyl CoA carboxylase
when are ketone bodies generated?
from fatty acid metabolism under prolonged starvation in type 1 diabetes
