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16. Lipids


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Where does fat digestion occur?
In the small intestine
What enzyme in the small intestine allows for fat digestion?
Pancreatic lipase
What allows H2O-soluble pancreatic lipase to act on lipids?
Emulsification with bile acids
What particular bile salt is important in emulsification?
What does pancreatic lipase do to lipids?
Breaks into monoglyceride and 2 free fatty acids.
What are micelles?
Aggregates of FFA's, monoglycerides, and bile acids -> allows solubility of the fat digestion products.
What is the purpose of micelles?
Uptake of fat digestion products from the small intestine into the enterocytes
What is the result of poor fat digestion in the intestine?
What is fat when it is eaten?
What happens after enterocytes uptake micelles? (2 possibilities)
1. Re-esterification of mono-glyceride+FFA to Triglyceride
2. Formation of chylomicrons
What are chylomicrons made of?
Triglyceride, Cholesterol, Cholesterol esters, surrounded by Protein and phospholipids.
What are chylomicrons a specific class of?
Where do chylomicrons go after formation in enterocytes?
To the lymphatic sytem, to the thoracic duct, into circulation.
What are the target tissues of chylomicrons?
-Adipose tissue
What are the normal body functions of lipids?
-Membrane components
-Insulate nerves
What happens to chylomicrons in circulation when they reach the tissue?
They get broken down to energy and chylomicron remnants for storage or energy use.
What enzyme is responsible for chylomicron breakdown in circulation?
Lipoprotein lipase
What is Cholesterol made from?
Acetyl Co-A
Where is cholesterol made?
In the liver and gut
What are 4 sterol derivatives?
-Hormones (steroids)
-Bile salts (by the liver)
-Vitamin D
What are the 5 classes of lipids?
1. Sterol derivatives
2. Fatty acids
3. Glycerol esters
4. Sphingosine derivatives
5. Terpenes
What are the terpenes?
Vitamins A, K, and E
Where is esterification of chylomicrons done? (going back)
In the vascular component
What 2 enzymes catalyze esterification?
-LCAT (lecithin)
-ACAT (acyl)
Which apolipoprotein may be associated with increased risk of Coronary artery disease (CAD)?
Apolipoprotein B
What methods are useful in measuring lipoproteins? (2)
What apolipoprotein is the major one in HDL?
Apo A
What is the more protective lipoprotein?
What apolipoprotein is the major on ein LDL?
Apo B
Which lipoprotein is associated with high risk of CHD?
List the lipoproteins:
What is the source of chylomicron?
the intestine
What is the source of VLDL?
the liver
What is the source of IDL and LDL?
What is the source of HDL?
VLDL and Chylomicrons
Where is HDL synthesized?
In the liver and intestines
Which lipoprotein has the highest percent of tryglyceride?
Which lipoprotein has the highest percent of cholesterol?
LDL! not hdl
What makes HDL so heavy?
It has the highest percent of protein
what lipid is important in fetal development?
DHA - from omega-3 fatty acids
How does DHA aid fetal develpment?
It provides structural fatty acid in brain gray matter and retinal tissue - important for brain and eye maturation.
What are the 4 general types of methods for lipid analysis?
1. Plasma appearance
2. Cholesterol measurement
3. HDL measurement
4. LDL measurement
What are specifications for evaluating plasma appearance?
Store at 4'C overnight; can use EDTA plasma
What are the 2 types of methods for total cholesterol measurement?
1. Enzymatic
2. Chemical
What is the principle of the enzymatic cholesterol method?
1. Cholesterol is broken down to produce peroxide;
2. Peroxide is broken down by 2a) Peroxidase -> color
2b) Catalase -> NADPH
What are 2 chemical methods for cholesterol measurement?
1. Liebermann-Burchard
2. Abell
which chemical method has higher sensitivity?
What is a drawback to the Liebermann-Burchard method?
It uses caustic reagents - H2SO4 and acetic anhydride.
What are 2 types of methods for HDL measurement?
1. Ultracentrifugation
2. Precipitation
List 4 reagents that will precipitate HDL:
1. Heparin-Manganese Chloride
2. Dextran Sulfate
3. Phosphotungstate
4. Polyethylene glycol
What is the preferred amt of HDL in the body, high or low?
HIGH - it helps prevent CHD
What are 2 options for measuring LDL?
1. Direct assay
2. Calculation
What is the calculation for LDL?
Friedwald calculation
What are limitations for doing the Friedwald calculation?
Can only be done on fasting specimens, with Triglyceride levels above (?) 400
What is the Friedwald calculation?
LDL = Total Chol - (Try/5)+HDL
How is LDL directly measured?
What is the WHO classification of hyperlipidemias based on?
Plasma appearance, Cholesterol levels, Triglyceride levels, and electrophoretic patterns.
How many WHO classes are there?
What pattern follows the WHO classes?
1 = Reference, Clear plasma
Type 1 = Milky
Type 2a = Clear
Type 2b = Clear-Turbid
Type 3 = Turbid
Type 4 = Turbid-Opaque
Type 5 = Super milky
What is Niemann-Pick disease?
Deficiency of enzyme Sphingomyelinase
What results from Niemann -Pick disease?
Excess sphingomyelin in the liver, spleen, brain, and bone marrow
Who is primarily affected by Niemann-Pick?
Children; usually die within several years.

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