LIPIDS Flashcards
● Comes from the greek word “Lipos” which means fat
LIPIDS
Refers to a collection of organic molecules of varying chemical
composition
LIPIDS
Are grouped together on the basis of their solubility in nonpolar
solvents
LIPIDS
4 main groups of lipids
→ Fatty Acids (Saturated and Unsaturated)
→ Glycerides (Glycerol-containing Lipids)
→ Nonglyceride Lipids (Sphingolipids,Steroids,Wax)
→ Complex Lipids (Lipoproteins)
→ When oxidized, each gram of fat releases 9 kcal of energy,
or more than twice the energy released by oxidation of a
gram of carbohydrate
● Energy Source
→ In the form of triglycerides (TAG) in adipocytes
● Energy Storage
● Cell Membrane Structural Components
→ Phosphoglycerides, sphingolipids, and steroids make up
the basic structure of all cell membranes
→ Hence cell membrane is referred to as phospholipid
bilayer
● Hormones
→ Steroid hormones
→ Lipid-soluble vitamins (A,D,E,K)
● Vitamins
→ Dietary fat serves as a carrier of the lipid-soluble vitamins
● Vitamin Absorption
→ fats as shock absorber
● Protection
→ subcutaneous fat
● Insulation
● Are long-chain monocarboxylic acids
A. FATTY ACIDS
▪ Less than 6 carbons
→ SHORT-CHAIN FATTY ACIDS
6-10 carbons
▪ Includes 11
MEDIUM CHAIN FATTY ACIDS
▪ More than 12 carbons
→ LONG-CHAIN FATTY ACIDS
→ No double bond
→ Each C being “saturated” with H
→ General Formula: CH3(CH2)nCOOH
● SATURATED FATTY ACIDS
Composed of at least one carbon-to-carbon double bond
→ Almost are in the cis configuration
● UNSATURATED FATTY ACIDS
→ Composed of one carbon-to-carbon double bond
● MONOUNSATURATED FATTY ACIDS
→ Composed of more than one carbon-to carbon double
bond
→ are identified by position of the double bond nearest the
methyl end (CH3 ) of the carbon chain; this is described
as an omega number;
● POLYUNSATURATED FATTY ACIDS (PUFA)
→ H’s on same side of the double bond; fold into a U-like
formation; naturally occurring
● cis-FATTY ACID
▪ the two hydrogen atoms will repel each other
● cis-FATTY ACID
→ H’s on the opposite side of the double bond; occur in
partially hydrogenated food
→ Straight structure
● trans-FATTY ACID
→ Double bond can be found only before the 9th carbon
atom
Essential
→ No double bond before the 9th carbon atom
● Nonessential
Fatty acids react with alcohols to form _______ and __________
ESTERIFICATION
esters and water
Producing fatty acids from esters
- Opposite of esterification
- ACID HYDROLYSIS
Is the base-catalyzed hydrolysis of an ester
- the product of this reaction, an ionized salt, is a soap
- SAPONIFICATION
Used in the food industry to convert
polyunsaturated vegetable oils into saturated
solid fats
- Hydrogenation
Carried out to add hydrogen to some, but not
all, double bonds in polyunsaturated oils
➔ In this way liquid vegetable oils are converted
into solid form (Crisco and margarine)
- Partial Hydrogenation
● Are lipid esters that contain the glycerol molecule and fatty
B. GLYCERIDES
– nonionic and nonpolar
- Produce after the esterification of glycerol with a
fatty acid
Neutral Glycerides
Esterification may occur at one, two, or all three
positions, producing:
Monoglycerides
o Diglycerides
o Triglycerides
have polar region, the
phosphoryl group, in addition to the nonpolar fatty acid
tails
Phosphoglycerides
→ Are lipids that are not derived from glycerol
→ Amphipathic and structural components of cellular
membrane
● SPHINGOLIPIDS
→ Derived from sphingosine (long chain, N-containing
alcohol)
● SPHINGOLIPIDS
→ Located throughout the body, but are particularly important
structural lipid components of nerve cell membranes
→ Found in abundance in the myelin sheath the surrounds
and insulate cells of the CNS
● SPHINGOMYELINS
→ Include the cerebrosides, sulfatides, and gangliosides
→ Are built on a ceramide backbone structure, which is a
fatty acid amide derivative of sphingosine
● GLYCOSPHINGOLIPIDS (GLYCOLIPIDS)
Are characterized by the presence of a single
monosaccharide head group
● CEREBROSIDES
ound in the membranes of
macrophage. If the head group is glucose.
- Consists of ceramide bonded to the hexose glucos
Glucocerebroside
– found almost exclusively in the
membranes of brain cells. If the head group is
galactose.
- Consists of ceramide joined to the monosaccharide
galactose
Galactocerebroside
→ Contain the steroid nucleus (steroid carbon skeleton)
STEROIDS
▪ known sterol, found in the membranes
Cholesterol
→ Amphipathic
→ Involved in the regulation of the fluidity of the membrane as a
result of the nonpolar fused ring
→ Hydroxyl group is polar
CHOLESTEROL
▪ chemical name of cholesterol
→ Perhydrocyclopentanophenanthrene ring
→ Can also exist in an esterified form called
cholesteryl ester
→ Are amphipathic derivatives of cholesterol
→ Synthesized in the liver and stored in the gallbladder
● BILE SALTS
– whose polar hydroxyl groups interact
with water and whose hydrophobic regions bind to lipids
Emulsifying agent
→ Contain fats
→ Act like your lipids. If steroid hormones are in your
bloodstream, it won’t mix with blood.
→ Needs a carrier to travel in your bloodstream.
→ Testosterone
→ Progesterone
→ Estrone, Estrogen, and its derivatives
→ Cortisone and Cortisol
→ Aldosterone
● STEROID HORMONES
→ Derived from many different sources and have a variety of
chemical compositions, depending on the source
WAXES
protective coating for hair and skin (used in skin
creams and ointments)
Lanolin
● Are bonded to other types of molecules
COMPLEX LIPIDS
▪ Has a lipid portion and a protein portion(apolipoprotein)
▪ Consist of a core of hydrophobic lipids surrounded by
amphipathic proteins, phospholipids, and cholesterol
LIPOPROTEINS
● Typically spherical in shape and range in size 10 to 1200 nm
● Composed of both lipids and proteins, called apolipoproteins
● Larger LPP particles have larger core regions (contain relatively
more TAG and cholesteryl ester)
→ Lighter; Lower density
LIPOPROTEINS
Classification (based on ultracentrifugation)
Chylomicrons [chylos]
● Very-low-density LPP [VLDL]
● Low-density LPP [LDL]
● High-density LPP [HDL]
Beta region
Very-low-density
pre beta region
LDL
○ alpha region
HDL
● Location: surface of LPP particles
APOLIPOPROTEINS
→ Help maintain the structural integrity of LPP
→ Serve as ligands for cell receptors
APOLIPOPROTEINS
● contain “amphipathic helix”
APOLIPOPROTEINS
→ Major protein on HDL
● Apo A-1
→ Is a large protein with MW 500 kD
→ Principal protein on LDL, VLDL, and Chylomicrons
● Apo B
Is found on LDL and VLDL
- Ligand for the LDL receptor
▪ Apo B-100
- Exclusively found in chylomicrons
▪ Apo B-48
→ Found in LDL, VLDL, and HDL
→ Serves as a ligand for the LDL receptor and the
chylomicron remnant receptor
→ Apo E2, Apo E3, Apo E4
● Apo E
Contain apo B-48
○ Account for the turbidity of
postprandial plasma
- Increased lipoprotein:
Chylomicrons
- Increased lipid: Triglycerides
○ Readily float to the top of stored
plasma and form a creamy layer
- chylous, turbid, milky, cloudy,
lipemic plasma/serum
○ Produced by the intestine
○ Deliver dietary (exogenous) lipids to
hepatic and peripheral cells
- most of which are triglycerides
CHYLOMICRONS
○ Contain apo B-100, apo E, and apo C
○ Produced by the liver
○ Rich in TAG like chylomicrons
○ Account for most of the turbidity observed in fasting
hyperlipidemic plasma specimens but do not form a top,
creamy layer
- VLDL is the increased lipoprotein when serum/plasma is
cloudy while patient is fasting
○ Major carriers of endogenous (hepatic derived) triglycerides
○ Transfer TAG from the liver to peripheral tissue
II. VERY LOW DENSITY LIPOPROTEIN
Contains apo B-100 and apo E
○ Primarily formed as a consequence of the lipolysis of VLDL
III.LOW DENSITY LIPOPROTEIN
○ Smallest and the most dense
○ Synthesized by both the liver and intestine
○ Can exist either as disk-shaped or as spherical-shaped
IV.HIGH DENSITY LIPOPROTEIN
Most active form in removing excess cholesterol from
peripheral cells
- Newly synthesized HD
○ DISCOIDAL HDL
▪ Larger in size and richer in lipid than HDL3
▪ May be more efficient in delivering lipids to the liver
- HDL2
2 plasma proteins that remodels your HDL:
Phospholipid transfer protein (PLTP)
- Cholesteryl ester transfer protein (CETP)
4 pathways
- Absorption pathway
- Exogenous pathway
- Endogenous pathway
- Reverse Cholesterol Transport Pathway
▪ Formed through the metabolism of VLDL in circulation;
lipid content, size, and density of IDL is intermediate
between VLDL and LDL
- Intermediate Density Lipoprotein
▪ is similar to LDL in terms of density and overall
composition, and can be thought of as an LDL particle
to which apo(a) has been added, linked to apoB-100
via a disulfide bond
- Lipoprotein (a)
▪ is an abnormal lipoprotein found in patients with
obstructive biliary disease, and in patients with familial
lecithin/cholesterol acyltransferase (LCAT) deficiency
- LpX Lipoprotein
▪ * is an abnormal lipoprotein that accumulates in type 3
hyperlipoproteinemia
- ẞ-VLDL Lipoprotein or Floating ẞ Lipoprotein
Minor lipoproteins
Intermediate density lipoprotein
Lpa
Abnormal lipoproteins
Lpx
B- VLDL Lipoprotein or floating B lipoproteins
Men and women both show a tendency toward increased
_______, ________, ________concentrations with age
TC, LDL, TAG
_____, ____, ______ and triglycerides in young children are generally much
lower than those seen in adults
TC, LDL, TAG
: Most likely to have coronary heart disease
Positive risk factors
Less likely to have coronary heart disease
Negative risk factor
NCEP
- National Cholesterol Education Program
Diseases associated with abnormal lipid
concentrations
DYSLIPIDEMIA
Genetic abnormalities
▪ Environmental/Lifestyle imbalances
▪ Develop secondarily, as a consequence of other
diseases
▪ Associated with CHD or arteriosclerosis
DYSLIPIDEMIA
→ 2 Categories of dyslipidemia
→ 2 Categories
3 SUBDIVISIONS:
of 3 SUBDIVISIONS:
Hypercholesterolemia
● Hypertriglyceridemia
● Combined hyperlipidemia
Most closely linked to heart disease
▪ Increased in LDL cholesterol
▪ Genetic abnormalities
- Hypercholesterolemia
▪ Genetic
▪ Individuals synthesize intracellular cholesterol
normally, but lack, or are deficient in, active LDL
receptors
→ FAMILIAL HYPERCHOLESTEROLEMIA
Result of an imbalance between synthesis and
clearance of VLDL in the circulation
- Hypertriglyceridemia
Genetic
▪ FAMILIAL HYPERTRIGLYCERIDEMIA
o Another ongoing disease
▪ Life-threatening abnormality because it can cause
acute and recurrent pancreatitis
▪ SECONDARY HYPERTRIGLYCERIDEMIA
Presence of elevated levels of serum total
cholesterol and triglycerides
▪ Considered at increased risk of CHD
- Combined Hyperlipoproteinemia
Currently thought to confer increased risk of CHD and
CVD
▪ Can block plasminogen, forming clots along the arterial
wall that will not be dissolved
- Lp(a) Elevation
Are abnormalities marked by decreased lipoprotein
concentrations
HYPOLIPOPROTEINEMIA
- is a disorder consisting of low levels of LDL
cholesterol or apolipoprotein B
- Hypobetalipoproteinemia
▪ Indicates an isolated decrease in circulating HDL
▪ Tangier Disease
▪ HDL concentrations as low as 1-2 mg/dL (0.03 – 0.05
mmol/L)
▪ Total chole as low as 50 – 80 mg/dL (1.3 – 2.1 mmol/L)
▪ mutations in the ABCA1 gene or the ABCA1
transporter, which mediates the first step of the reverse
cholesterol transport pathway
▪ ↓APO A-1
HYPOALPHALIPOPROTEINEMIA
LCAT DEFICIENCY
2 FORMS
● Complete (homozygous)
● Mild (heterozygous)
Corneal clouding
○ Nephropathy
○ Hemolytic anemia
○ HDL deficiency
CNHH
● Complete (homozygous)
● Complete (homozygous)
● Mild (heterozygous)
