Lipids & Lipoproteins Flashcards
What are some classifications of lipids?
- fatty acids
- glycerol esters
- sterols
- terpenes
- sphingosine derivatives
What are some examples of fatty acids?
- palmitic
- linoleic
What are some examples of glycerol esters?
triglycerides
What are examples of sterols?
- cholesterol
- hormones
- vitamin D
What are some examples of terpenes ?
- vitamins A, E, K
What’s an example Sphingosine derivatives ?
Sphingomyelin
What are the routine lipid analysis measurements ?
- total cholesterol
- HDL cholesterol
- LDL cholesterol
- triglycerides
Briefly describe cholesterol
- used for the synthesis of steroid hormone, bile acids & vitamin D
- plays a role in membrane properties
Describe Biosynthesis
- occurs in liver/intestine & tightly regulated
- rate limiter = HMG CoA reductase –> this enzyme inhibited by the statins
- 70% of circulating cholesterol was synthesised in the liver - not from diet
Describe Chylomicrons
- composed mainly of triacylglycerols
- these are degraded & fatty acids delivered to the adipose tissues
- remnant chylomicrons are degraded by liver microsomes
- repacked as VLDL (very low density Lipoproteins)
Define VLDL
Very Low Density Lipoproteins
Describe VLDL
- rich in triacylglycerols
- this protein is involved in activation of lipoprotein lipase
Describe how Lipoprotein Lipase acts
lipoprotein lipase -> VLDL –> Glycerol + fatty acids –> adipose tissue
Define IDL
Intermediate Density Lipoprotein
- smaller, more dense version of VLDL particle
How it IDL converted to LDL ?
- Continuing action of lipoprotein lipase
- enrichment of IDL with cholesterol esters from HDL
- regulated by CETP
Define CETP
Cholesteryl Ester Transfer Protein
Describe LDL
- 40% cholesterol esters
- important for delivering cholesterol to tissues
- single protein moiety - apolipoprotein B100
What does HDL do ?
transports cholesterol from dead & apoptotic cells back to the liver
- can also exchange cholesterol with LDL - CETP
Why is patient fasting important ?
- essential for triglyceride as this can remain at higher conc. in plasma for several hours after a meal
What are some sampling-considerations that should be considered ?
- change from upright to supine position can reduce cholesterol
- prolonged tourniquet application can increase cholesterol from 5-15%
- cholesterol is slightly higher in winter than in summer - opposite is true for triglycerides
What’s the normal range for cholesterol ?
should be less than 5 mmol/L
How is LDL cholesterol typically calculated ?
Using the Friedwald formula
How often should people between 40-75 years old have cholesterol tests?
every 5 years
How often should you have a cholesterol test if you’re on cholesterol lowering medication?
Every 12 months
