Metabolism S5 - Lipid Transport and Byproducts of Energy Metabolism Flashcards
How are lipids transported in the blood?`
98% via lipoprotein particles
2% bound to albumin
What are the albumin bound fatty acids in the blood used for and where do they come from?
Used as fuel by tissues
Fatty acids released from adipose tissue during lipolysis and bind to albumin in blood
What is the maximum normal level of Fatty acids in the blood and why is it limited to this value?
~3mM
Limited carrying capacity of albumin
Why are plasma lipoproteins significant to medicine?
Disorders in their metabolism are associated with important diseases such as athersclerosis and coronary artery disease
What is the term for the protein components of a lipoprotein?
Apoproteins
What are the functions of apoproteins?
Packaging lipids into water soluble form
Activation of enzymes
Recognition of cell surface receptors
Why are Apoproteins well suited to lipid packaging in plasma?
Have hydrophobic regions that interact with lipids and hydrophilic regions that interact with water
Describe the general structure of Lipoproteins
Spherical particles with a surface coat and hydrophobic core
What might a surface coat of a lipoprotein contain?
Phospholipids
Cholesterol
Apoproteins
What might a lipoprotein core contain?
Cholesterol esters
TAGs
What is a lipoprotein’s stability dependent on?
Lipoproteins only stable if they maintain their spherical shape, this is dependent on the ratio of core to surface lipids
Explain how removal of lipids from core or coat is performed
In core, when lipids removed other lipids from coat must be removed to maintain stability of lipoprotein.
Many components of coat are free to transfer however some must be removed by special proteins (eg. Lipase or transfer proteins).
What are the 4 major types of lipoprotein?
Chylomicrons
VLDL
LDL
HDL
What is the basic function of Chylomicrons?
Transport of dietary TAGs from intestine to tissues such as adipose tissue
Where are chlyomicrons produced?
Epithelia of small intestine
How are chylomicrons transported? From where to where?
Chylomicrons released from small intestine epithelia into lymphatic vessels that drain into the bloodstream.
The bloodstream then transports them to adipose tissues
In the small intestine epithelia what are TAGs packaged with in chylomicrons?
Other dietary lipids such as cholesterol and ADEK vitamins
How are TAGs in chylomicrons converted to fatty acids and glycerol in adipose tissue?
Adipocytes express extracellular lipoprotein lipase which hydrolyses TAGs to release fatty acids into the adipose cells
What processes must occur to produce TAGs in the small intestine epithelia from TAGs in the intestine’s lumen?
Pancreatic lipase hydrolyses TAGs to release glycerol and FAs which are absorbed by epithelia whereupon they are re-esterified using glycerol phosphate
What is the transport function of VLDL?
Transport of TAGs synthesised in the liver to adipose tissues for storage
What is the transport function of LDLs?
Transport of cholesterol synthesised by the liver to adipose tissues for storage
What is the transport function of HDL?
Transport of excess cholesterol to the liver for disposal as bile salts.
What is the function of lipoprotein lipase?
Hydrolysis of TAGs in lipoprotein (such as chylomicrons or VLDLs) core releasing fatty acids and glycerol