BCCB2000 Lecture Notes - Lecture 21: Liver Disease, Electron Transport Chain, Malabsorption
22 Jun 2018
School
Department
Course
Professor
Fatty Acid Metabolism
Dr Steven Bottomley
Why are Fats Good Stores of Energy?
-The long chain alkyl hydrocarbon chains of fatty acids have an energy of
oxidation more than twice that for the same weight of carbohydrate or protein
-Other useful properties are that triacylglycerols are segregated into lipid
droplets which do not raise the osmolarity of the cytosol and do not contain
extra weight as water of solvation (as do polysaccharides)
-Their relative chemical inertness allows intracellular storage in large quantities
without the risk of undesired chemical reactions with other cellular constituents
-Oxidation of fatty acids is a central energy yielding pathways in animals,
protists, and some bacteria. Stored triacylglycerols are virtually the sole source
of energy in hibernating animals and migrating birds
-Triacylglycerols provide more than half the energy requirements of some
organs, particularly the liver, heart, and resting skeletal muscle
-The same properties which make triacylglycerols good storage compounds also
create problems for their role as fuels e.g. insolubility in water
oLipids have to be solubilised by micelle formation or packaged into
chylomicrons and lipoproteins for transport between tissues
Dietary Lipids:
-Digestion
oStomach
Lipase degrades triacylglycerols containing short and medium
chain fatty acids
oSmall intestine
Emulsification
By bile salts
Larger surface area and solubilise lipids so enzymes can
act upon them
Degradation by enzymes
Pancreatic enzymes secreted into the small intestine
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Products are fatty acids, 2-monoaculglycerol, and
cholesterol
Absorption
Mixed micelles of lipid products
Dietary Lipids Transport:
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find more resources at oneclass.com
Stored Lipids Mobilisation and Transport:
-Mobilisation occurs when storage triacylglycerols are brought out of storage,
through the action of hormones, and converted to fatty acids
o95% of biologically available energy in triacylglycerols is in their three
long chain fatty acids. Only 5% is contributes by glycerol
-The fatty acids are then transported (diffuse into the blood and hitch a ride on
serum albumin and other proteins) to those tissues which can oxidise them for
energy production
oSkeletal muscle, heart, liver, and renal cortex
-Fatty acids diffuse into cells
Activation and Intracellular Transport:
-The β-oxidation of fatty acids takes place in the mitochondrial matrix, but the
inner mitochondrial membrane is impermeable to fatty acids
-Therefore, there has to be some way of transporting fatty acids into the
mitochondrial matrix
-This step consists of cytosolic activation of fatty acids and two reactions for
entry of activated fatty acid into mitochondria matrix through a carnitine
shuttle transport reaction mechanism
oThis is the rate limiting step for the β-oxidation of fatty acids
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The long chain alkyl hydrocarbon chains of fatty acids have an energy of oxidation more than twice that for the same weight of carbohydrate or protein. Other useful properties are that triacylglycerols are segregated into lipid droplets which do not raise the osmolarity of the cytosol and do not contain extra weight as water of solvation (as do polysaccharides) Their relative chemical inertness allows intracellular storage in large quantities without the risk of undesired chemical reactions with other cellular constituents. Oxidation of fatty acids is a central energy yielding pathways in animals, protists, and some bacteria. Stored triacylglycerols are virtually the sole source of energy in hibernating animals and migrating birds. Triacylglycerols provide more than half the energy requirements of some organs, particularly the liver, heart, and resting skeletal muscle. Lipase degrades triacylglycerols containing short and medium chain fatty acids: small intestine. Larger surface area and solubilise lipids so enzymes can act upon them.
