Exam 3 - Lipoproteins Flashcards
Ideal healthy level of total cholesterol
<200 mg/dl
Ideal healthy level of LDL - cholesterol
<100 mg/dl
Ideal healthy level of HDL - cholesterol
> 60 mg/dl
Ideal healthy level of triglycerides
<150 mg/dl
Most abundant lipids in the body
- triglycerides
- phospholipids
- cholesterol
Which lipid is a major source of energy for cells?
Triglycerides
Major lipid component of cell membranes
Phospholipids
Majority of cholesterol is made in the:
Liver
Function of cholesterol
- cell growth
- cell division
- membrane repair
- steroid/hormone production
- bile salts
Triglycerides structure
3 fatty acids to glycerol via ester linkage
high density energy store
Phospholipids structure
2 fatty acids linked to glycerol backbone, with phosphate/polar head group
Cholesterol is made into a cholesterol ester via what enzyme?
LCAT (lecithin cholesterol acyltransferase)
Cholesterol from the diet is only found in:
Animal fat
Cholesterol biosynthesis occurs primarily in the liver using:
Acetyl-CoA
Degradation of cholesterol only occurs in the:
Liver
What forms of metabolic fuel are found in the blood?
- glucose
- fatty acids
After eating, glucose becomes ____ and excess gets converted into ____
oxidized; glycogen
What form of fuel is used during fasting?
Fatty acids
Metabolic fuels are used ____
Inversely
____% of fatty acid is present as free fatty acid form (unesterified)
2-5% (95% in the form of fatty acid esters)
Free fatty acids are derived from:
- intracellular hydrolysis of triglycerides in hepatic or adipose cells
- lipoprotein lipase acting on circulating lipoproteins
During a fed state, insulin inhibits ______ and stimulates ____ and ____
hormone-sensitive lipase; triglyceride synthesis and LPL
Insulin during fed state results in:
Storage of triglycerides (don’t need to use fatty acids as fuel if glucose is present)
During fasting, there is a drop in ____ which activates _____ (enzyme). ____ are hydrolyzed in adipocytes
Insulin; hormone sensitive lipase; Triglycerides
Hormone sensitive lipase function
Make fatty acids available to cells/tissues that need it (in presence of insulin)
Function of lipoprotein lipase
Removes fatty acids off of lipoproteins so they can be mobilized/stored in the fat cell
True or false: lipids can be transported without aid in the bloodstream
False - they are insoluble so they need to be associated with lipoproteins for transport
Lipoprotein structure
- spherical soluble particle
- nonpolar lipids in core (TG and cholesterol esters)
- polar aspects toward aqueous phase
Where are apoproteins located with respect to the lipoprotein?
On the outside (outermost) in aqueous phase
What are apoproteins?
Proteins associated with lipoproteins
Functions of apoproteins
- structural role
- binding sites for receptors
- activators or co-enzymes for lipid metabolism
____ direct the fate of lipoproteins
Apoproteins
What are the different classifications of lipoproteins?
- Chylomicrons
- VLDL
- IDL
- LDL
- HDL
Which lipoprotein has the highest density? Why?
HDL - lowest amount of triglycerides and smallest
Largest lipoprotein
Chylomicron (also least dense)
Density of lipoproteins is based on:
Buoyant density compared to physiological saline
Larger lipoprotein particles means that there is:
- higher content of triglycerides
- lower density
Smaller lipoprotein particles means there is:
- less triglycerides
- greater relative mass of protein
- enriched in cholesterol esters
- greater density
Lipoproteins on gel electrophoresis - what is significant about chylomicrons?
Trapped at origin (much larger in size so they get stuck)
Apoproteins can be exchanged between different lipoproteins except for:
Apo B100 and Apo B48
True or false: Apo B100 and Apo B48 can exist on the same lipoprotein particle
False - only one or the other
Between different lipoproteins, protein content can vary such as:
Number and types of proteins associated with them
Besides proteins, what else can be exchanged between lipoproteins?
- Surface phospholipids and cholesterol
- cholesterol esters and TGs (but needs cholesterol ester transfer protein)
Source of chylomicrons
Gut/intestine
Chylomicrons - apoproteins associated
- B48
- CII
- E
Function of chylomicrons
- transport dietary triglycerides
- FFA goes to adipose/muscle
- cholesterol esters goes to liver as remnants
Source of VLDL
Liver
VLDL - apoproteins associated
- B100
- CII
- E
VLDL function
- transports endogenous triglycerides
- FFA goes to adipose/muscle
- cholesterol esters go to LDL
Source of LDL
Blood (remnant of VLDL)
LDL apoproteins associated
B100
LDL function
- transports cholesterol (from VLDL) to peripheral tissues
- cholesterol esters go to liver and peripheral cells