Lipids and Lipoproteins Flashcards
Lipids are commonly referred to as
Fats
Lipids are composed mainly of
C-H bonds; sometimes C-H-O bonds
Important roles of lipids
Storing energy
Aiding in proper digestion and absorption of food
Acting as structural components on cell membranes
Acting as messengers and signaling molecules within the body
Lipid soluble substances
Vitamins A, D, E, K
Lipids can also be used to synthesize other compounds in the body like steroid hormones. True or False?
True
Precursors of Steroids
Cholesterol
Examples of Steroid Hormones
Estrogen
Progesterone
Testosterone
Androgen
Lipids are soluble in water, but insoluble in organic solvents. True or False?
False; Lipids are insoluble in water (nonpolar), but soluble in organic solvents (chloroform and ether)
Special transport mechanism for lipids to be circulated in blood
Lipoproteins
Lipids transported by lipoproteins
Triglycerides (Triacylglycerol/TAG)
Phospholipids
Cholesterol
Components of Phospholipids
Lipids with attached phosphate groups
Components of Cholesterol
Carbon ring structure with alcohol functional groups
Cholesteryl esters
4 major classes of lipids
Fatty acids
Triglycerides
Phospholipids
Cholesterol
Linear chains of C-H bonds that terminate with a carboxyl group (-COOH)
Fatty acids
Components of TAG
3 Fatty Acid + 1 glycerol molecule
Number of carbon atoms in short-chain fatty acids
4-6 carbon atoms
Number of carbon atoms in medium-chain fatty acids
8-12 carbon atoms
Number of carbon atoms in long-chain fatty acids
> 12 carbon atoms
Straight chain compounds with even number of carbons (4-24 carbon atoms)
Dietary fatty acids
Fatty acid without double bonds
Saturated fatty acid
Example of fatty acid
Palmitic acid
Fatty acid with one double bond
Monounsaturated fatty acid
Example of monounsaturated fatty acid
Oleic acid
Fatty acid with two or more double bonds
Polyunsaturated fatty acid
Examples of polyunsaturated acid
Linoleic acid
Linolenic acid
Omega-3
Omega-6
Omega-9
Benefits of omega fatty acids
Lowers the risk of CVD
Consumption of trans fatty acids is good for patients with Congenital Heart Disease. True or False?
False; Consumption of trans fatty acids increases the risk of Congenital Heart Disease
Major dietary trans fatty acid
Elaidic acid
Contain three fatty acid molecules attached to one molecule of glycerol by ester bonds
Triglycerides
Main storage form of lipids
Triglycerides
TAG is also known as
Neutral Fat
Consistency of triglycerides containing saturated fatty acids, which do not have bends in their structure
Solid at RT
Consistency of triglycerides, containing cis unsaturated fatty acids
Oils at RT
Similar with TAG but have two esterified fatty acids
Phospholipids
Phospholipids are amphipathic. True or False?
True
Forms of phospholipids
Lecithin/ Phosphatidylcholine - 70%
Sphingomyelin - 20%
Cephalin - 10%
Composition of myelin in the axons of the neurons
Sphingomyelin
Examples of cephalin
Phosphatidyl ethanolamine
Phosphatidyl serine
Lysolecithin + Inositol Phosphatide
The only phospholipid in membranes that is not derived from glycerol but from an amino alcohol
Sphingomyelin
Sphingomyelin is derived from
Sphingosine
Accumulation of sphingomyelin in the liver and spleen is seen in
Niemann-Pick disease
An unsaturated steroid alcohol containing four rings (A, B, C, and D)
Cholesterol
Amphipathic lipid found on the surface of lipid layers along with phospholipids
Cholesterol
Characteristics of cholesterol
Can be converted in the liver to primary bile acids (Cholic acid and chenodeoxycholic acid)
Can be converted to steroid hormones (glucocorticoids, mineralocorticoids, and estrogens)
Can also be transformed to vitamin D3
2 forms of cholesterol
Esterified / cholesteryl ester (70%)
Unesterified / free cholesterol (30%)
Form of cholesterol that forms an ester bond with another molecule
Esterified / cholesteryl ester
Cholesterol is used as precursor the synthesis of different steroid hormones and vitamin C. True or False?
False; Vitamin D
Increased cholesterol in blood
Hypercholesterolemia
Increase of fats in the blood
Hyperlipidemia
Cholesterol: Animal; _____: Plants
Phytosterol
Cholesterol is not readily catabolized by most cells and, therefore, an excellent source of fuel. True or False?
False; Does not serve as source of fuel
Characteristics of phytosterols
Lower plasma total cholesterol and LDL-C
Raise HDL-C
Catalyzes the esterification of cholesterol
LCAT (Lecithin-Cholesterol Acyltransferase)
Organ that synthesize LCAT
Liver
The activator of LCAT
Apo A-1
Enables HDL to accumulate cholesterol as cholesterol ester
LCAT (Lecithin-Cholesterol Acyltransferase)
Liberating cholesterol or breaking ester bonds
Saponification
Importance of APO A-1 and HDL
APO A-1 is a composition of HDL which helps in the activation of LCAT and esterification of cholesterol
Cholesterol can be converted in the liver to primary bile acids. True or False?
True
Cholesterol can be converted to steroid hormones. True or False?
True
Cholesterol can be transformed to vitamin K. True or False?
False; Vitamin D3
Examples of primary bile acids
Cholic acid
Chenodeoxycholic acid
Examples of steroid hormones
Glucocorticoids
Mineralocorticoids
Estrogens
Macromolecule of lipids and proteins
Lipoproteins
It constitutes the body’s “petroleum industry”
Lipoproteins
Shape and size of lipoproteins
Spherical; 10-1200 nm
Lipoprotein surface is composed of
Amphipathic phospholipids and
cholesterol
Lipoprotein core is composed of
Neutral triglycerides and cholesteryl ester
Protein associated to plasma lipoproteins
Apolipoproteins
Where does apolipoproteins are located?
Surface of lipoprotein particles
Functions of apolipoproteins
Help maintain the structural integrity of lipoproteins
Help to keep lipids in solution during circulation through the blood stream
Interact with specific cell-surface receptors and direct the lipids to the correct target organs and tissues in the body
Serve as ligands for cell receptors and as activators / inhibitors of the various enzymes that modify lipoprotein particles
Aid in the solubilization of lipids in the circulation
Responsible for the ability of apolipoproteins to bind to lipids
Amphipathic helix
Major protein of HDL
Apo A
Function of Apo A-I
Major activator of LCAT
Function of Apo A-II
Activates hepatic lipase
Function of Apo A-IV
Cofactor of LCAT
Principal protein of LDL, VLDL, and chylomicrons
Apo B
Function of Apo B-100
Binds to LDL/VLDL cell receptor
Function of Apo B-48
Structural role in chylomicrons
Major protein of VLDL
Apo C
Function of Apo C-I
Activates LCAT
Function of Apo C-II
Potent activator of LPL
Function of Apo C-III
Regulates rate of clearance of TAG – rich lipoprotein (inhibit LPL)
Apo A-III, thin line apolipoprotein, serves as lysolecithin carrier
Apo D
Function of Apo E
Serves as a ligand for the LDL receptor and the chylomicron remnant receptor
Genotypes of Apo E
Apo E2
Apo E3
Apo E4
Apo E2 is an indication of
Increased risk for developing Type III hyperlipoproteinemia
Most common Apo E genotype that doesn’t seem to influence risk
Apo E3
Apo E4 is an indication of
Increased risk for developing Alzheimer’s disease
Main purpose of lipoproteins
Delivery of fuel to peripheral cell
Largest lipoprotein particles
Chylomicrons
Diameter of chylomicrons
80-1200 nm
Least dense lipoprotein particles
Chylomicrons
Density of chylomicrons
<0.93 g/mL
Appearance of chylomicrons in plasma when stored for hours at 4 degCel
Turbid (milky appearance)
Apolipoprotein in chylomicrons
Apo B-48
Organ responsible for the production of chylomicrons
Intestine
Chylomicrons are rich in phospholipids. True or False?
False; rich in triglycerides
Principal role of chylomicrons
Transportation of triglycerides and cholesterol to the peripheral tissue and liver
VLDLs are produced primarily by the
Liver
Apolipoproteins in VLDL
Apo B-100
Apo E (MAIN)
Apo C
Appearance of VLDL in fasting hyperlipidemic plasma specimens
Turbid; without a creamy top layer
Principal function of VLDL
Carry and transfer endogenous triglycerides from liver to peripheral tissue for energy utilization and storage
Intermediate-Density Lipoproteins (IDLs) are also known as
VLDL remnants
(After conversion of VLDL to LDL)
IDLs are primarily seen in normal plasma. True or False?
False; cannot be seen in normal plasma