Introduction to lipids Flashcards
What are the four pathways for lipid transport?
The four pathways for lipid transport are:
•Exogenous: From gut (digestive tract) to periphery
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•Endogenous: From liver to periphery
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•Reverse: From periphery to liver
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•Bile production: From liver into digestive tract
What lipoproteins transport fat in the exogenous pathway, and where are they taken up?
Lipids from the diet are packaged by the small intestine into chylomicrons, which are taken up by the liver (or by periphery)
What lipoproteins transport fat in the endogenous pathway, and where are they taken up?
Lipids made in the liver are packaged into VLDL, which is taken up in the periphery.
What lipoproteins transport fat in the reverse cholesterol transport, and where are they taken up?
Lipids from the periphery are packaged into HDL, and are taken up by the liver.
Where in the periphery are most lipids stored and used?
The peripheral lipids are stored in adipose tissue and muscle tissue.
What are the conditions for reverse cholesterol transport to occur?
Reverse cholesterol transport, indicated by HDL in the blood, occurs when the lipid supplies in the liver are being exhausted, and is a sign of reduced body lipid.
Please give a brief description of the bile production and recycling.
Bile is produced from cholesterol in the liver. It is then released into the gut and gall bladder from the liver, via the cystic duct. In the gut, most bile acids are absorbed, and returned to the liver, where they are recycled.
What is the main function of lipoprotein lipase?
Lipoprotein lipase metabolises triglycerides, so that they can be removed from VLDL and moved across the capillary membrane of blood vessels.
Lipoprotein lipase metabolises triglycerides into fatty acids and glycerol.
What are apolipoproteins, and what do they do?
Apolipoprotein is an amphipathic lipid-carrying protein in lipoprotein particles. Lipids are not soluble in plasma, and must be carried by lipoproteins, which are soluble in plasma.
Please explain why big lipoprotein particles have lower density compared to smaller lipoproteins.
Lipids have much lower density than proteins, akin to the way fat has lower density than water. Bigger lipoprotein particles tend to carry a lot of triglycerides, which have very low density. They are therefore lower in density than proteins and cholesterol, which make up a larger percentage of smaller lipoprotein particles.
Why is Low Density Lipoprotein (LDL) the most dangerous?
Low Density Lipoprotein (LDL) can store blood cholesterol that is not stored elsewhere.
LDL is an indicator of excess lipids in the body being transported from liver to periphery. Excess LDL and LDL contents, including cholesterol esters, accumulates in atheromas, the beginnings of atherosclerosis.
Why is High Density Lipoprotein (HDL) an indicator of cardioprotection?
High Density Lipoprotein (HDL) transports lipids from fat cells to the liver in reverse cholesterol transport. This is when cholesterol is being consumed, so HDL is an indicator of low lipid states.
Why does Very Low Density Lipoprotein (VLDL) indicate a risk of atherogenesis?
VLDL transports triglycerides and endogenous cholesterol from the liver to adipose and muscle tissue. In the periphery, triglycerides are removed from the VLDL, leaving IDL, which is an intermediate step in the production of LDL.
What is Intermediate Density Lipoprotein (IDL)?
IDL is a lipoprotein particle in the blood, which is a product of VLDL losing triglycerides to periphery. IDL then becomes LDL.
What does a chylomicron do?
A chylomicron carries exogenous lipids (fats from the diet) from the gut to the periphery. It is elevated after eating fatty meals, but does not generally signify CV risk.
