C - Chapter IX: Lipids and Lipoproteins Flashcards
: organic substances which are soluble in nonpolar organic solvents (chloroform and ether) and insoluble in polar solvents (water)
Lipids
nonpolar organic solvents
(chloroform and ether)
polar solvents
(water)
: yield fatty acids on hydrolysis OR complex alcohols the can combine with fatty acids to form esters
Lipids - chemically
: cholesterol, triglycerides, phospholipids and non-esterified fatty acids
human plasma lipids
: macromolecule which consists of varying proportions of protein, cholesterol, triglyceride and phospholipid
Lipoproteins
water-soluble, thus, it facilitates the transport of the lipids in the circulation
Lipoproteins
are diverse in terms of their structure and function
Lipids
Secondary energy source
TRIGLYCERIDE / Neutral FAT
Serves as a thermal insulator
TRIGLYCERIDE / Neutral FAT
Protects tissues from physical trauma
TRIGLYCERIDE / Neutral FAT
Precursor of biological hormones
CHOLESTEROL
Source of bile acids
CHOLESTEROL
Component of the Cell membrane
CHOLESTEROL
Component of the Cell membrane
PHOSPHOLIPIDS
Associated with vital life processes (e.g. CNS)
PHOSPHOLIPIDS
also known as triacylglycerol
TRIGLYCERIDES
transported by chylomicrons (exogenous) and VLDL (endogenous)
TRIGLYCERIDES
Complete Hydrolysis:
3 FA + glycerol
Partial Hydrolysis:
2 FA + monoglyceride
Absorption: = via the portal route
Glycerol (H2O-soluble)
Absorption: = via the lymphatic route
Fatty acids (H2O-insoluble)
Monoglyceride (H2O-insoluble)
Synthesis of TG from
monoglyceride & glycerol
: degradation of the fatty acids by 2C atoms with subsequent production of Acetyl CoA
β-oxidation of fatty acids in the mitochondria
found exclusively in animals and humans
CHOLESTEROL
contains cyclopentanoperhydrophenanthrene ring
CHOLESTEROL
contains 27 C atoms
CHOLESTEROL
(?) in the intestines comes from the diet, bile, intestinal secretions and cells
cholesterol
to be absorbed, it has to solubilized by the formation of mixed micelles containing unesterified cholesterol, fatty acids, monoglycerides, phospholipids and conjugated bile acids
cholesterol
90% of body’s (?) is synthesized by the liver and gut from simpler molecules like Acetyl CoA
cholesterol
complexing of cholesterol with a fatty acid; this process enhances the lipid carrying capacity of lipoproteins
Esterification
is mainly esterified in the vascular compartment
Cholesterol
Cholesterol
Catalyzed by:
− LCAT
− ACAT
− LCAT –
Lecithin Cholesterol Acyltransferase (in plasma)
− ACAT –
Acyl Cholesterol Acyltransferase (intracellularly)
transported by LDL to the cells
Cholesterol
transported by HDL out of the cells
Cholesterol
(?) that reaches the liver is either secreted unchanged into bile (free cholesterol) or metabolized to form bile acids
cholesterol
LIPOPROTEINS: MAJOR CLASSES
- Chylomicron (CM)
- Very-Low-Density Lipoprotein (VLDL)
- Intermediate Density Lipoprotein (IDL)
- Low-Density Lipoprotein (LDL)
- High-Density Lipoprotein (HDL)
Synthesized & released from the SI (Exogenous pathway)
Chylomicron (CM)
very rich in triglycerides (80%)
Chylomicron (CM)
transports dietary fat
Chylomicron (CM)
relatively poor in cholesterol, phospholipids and proteins
Chylomicron (CM)
Proteins: Apo B-48, AI, AII, AIV, C (1-2%)
Chylomicron (CM)
when present in high levels : milky plasma (floating creamy layer)
Chylomicron (CM)
synthesized and released from the liver
Very-Low-Density Lipoprotein (VLDL)
transports cholesterol & triglyceride which are synthesized in the liver (endogenous pathway)
Very-Low-Density Lipoprotein (VLDL)
smaller than chylomicrons
Very-Low-Density Lipoprotein (VLDL)
elevated levels produce a turbid plasma
Very-Low-Density Lipoprotein (VLDL)
contain : 50% triglycerides, 40% cholesterol and phospholipid, 10% protein
Very-Low-Density Lipoprotein (VLDL)
Proteins: Apo B-100 & Apo C-II
Very-Low-Density Lipoprotein (VLDL)
endogenous pathway
Very-Low-Density Lipoprotein (VLDL)
Exogenous pathway
Chylomicron (CM)
derived from VLDL hydrolysis by lipoprotein lipase (LPL)
Intermediate Density Lipoprotein (IDL)
partly depleted of triglyceride
Intermediate Density Lipoprotein (IDL)
contains an almost equal amount of triglyceride & cholesterol
Intermediate Density Lipoprotein (IDL)
Proteins: Apo B and E
Intermediate Density Lipoprotein (IDL)
produced from the action of LPL on IDL
Low-Density Lipoprotein (LDL)
consists of 50% cholesterol, 25% protein, 20% phospholipid and 5% of triglycerides
Low-Density Lipoprotein (LDL)
produced & catabolized in the liver & intestines
High-Density Lipoprotein (HDL)
Contains Apo AI & Apo AII
High-Density Lipoprotein (HDL)