1. CHAPTER 8
LIPIDS
 Definition of Lipids
 Functions of Lipids

2. Classification of lipids:
2. Fatty acids
- Fatty acyls
- made up of hydrocarbon chain
terminates with a carboxylic group.
- the carbon chain, typically
between four to 24 carbons long, maybe
saturated or unsaturated.

5. Biologically important fatty acids:
a. Eicosanoids
-are signaling molecules made by
oxygenation of twenty-carbon essential
fatty acids (EFAs).
-derive from either omega-3 (ω-3) or
omega-6 (ω-6) EFA.
- prostaglandins, prostacyclins,
the thromboxanes and the
leukotrienes.

6.  Prostaglandins: different types
 Some stimulate contraction of smooth muscle
during menstruation and labor
 Others produce fever and inflammation and
pain
 Thromboxanes: act in the formation of
blood clot
 Leukotrienes: induces contraction of the
muscle lining the lungs
 overproduction leads to asthma

7. 2. Glycerolipids
-are composed mainly of mono-, di- and
tri- substituted glycerols, the most well-
known being the fatty acid esters of
glycerol (triglycerides).
- - energy storage.

8. Triacylglycerides
 Glycerol in blue
 Fatty acids in red
 Condensation produces
3 water molecules

9. 3. Glycerophospholipids-phospholipids
- are ubiquitous in nature and are key
components of the lipid bilayer of cells
-involved in metabolism and cell
signaling.

11. Phosphoacylglycerols/
Phosphoglycerols
O
H2C O R1
O
O HC O R2
X O P O CH2
O

12. Phosphatidyl choline with fatty
acids as oleate and palmitate
O
H2C O O (CH2)7 C C (CH2)7 CH3
H H
O HC O (CH2)14 CH3
CH3
+ O P O CH2
N
H3C O
CH3

13. 4. Sphingolipids
- are a complex family of compounds that
share a common structural feature
- a sphingoid base backbone.

14. Sphingolipids
 Different types are found in plasma
membrane and myelin sheaths
 Gangliosides
 cell to cell interactions
 antigenic

15. Sphingolipids
X name
H
HO C C C (CH2)12-CH3
H H H ceramide
O
monosaccharide cerebroside
HC N R
H carbohydrate ganglioside
X O CH2 sphingomyelin

16. Sphingophospholipid with choline
and the fatty acid as linolenic
H
HO C C C (CH2)12-CH3
H H
O
O HC N (CH2)7 CH CH CH2 CH CH CH2 CH CHCH2CH3
H
CH3
+ O P O CH2
N
H3C O
CH3

17. 5. Sterol lipids
-such as cholesterol and its derivatives,
are an important component of
membrane lipids, along with the
glycerophospholipids and
sphingomyelins.

18. Role of Cholesterol
 Keeps the lipids in membrane from
aggregrating: Keeps the membrane intact
as a bilayer
 Precursor to Bile Acids
 Act as detergents to dissolve dietary fats
 Fats can be broken better by enzymes
 Precursor to steroid hormones that
regulate gene expression
 Precursor to Vitamin D

19. Good vs. Bad Cholesterol
 Related to lipoproteins (protein + lipid
complexes)
 Dietary excess fat is packaged into VLDL
 Fat cells (adipose cells) take these up convert
to fatty acids
 Some VLDL is converted to LDL
 LDL is very rich in Cholesterol

20. LDL VS. HDL
LDL
 Too much LDL can circulate in the blood
 Build up in arteries; lead to heart attack
HDL
 Another lipoprotein that converts
cholesterol into a lipoprotein that returns
to the liver ; Removes cholesterol out of
the bloodstream;
 believed to prevent heart attacks

21. Ratio of LDL to HDL
 LDL cholesterol of less than 100 mg/dL is the
optimal level. Less than 130 mg/dL is near
optimal for most people.
 A high LDL level (more than 160 mg/dL or 130
mg/dL or above if you have two or more risk
factors for cardiovascular disease) reflects an
increased risk of heart disease
 Low HDL cholesterol levels [less than 40 mg/dL]
is thought to increase the risk for heart disease.

22. 6. Prenol lipids
Biologically important prenol lipids:
a. Carotenoids are important simple
isoprenoids that function as antioxidants and
as precursors of vitamin A.
b. Vitamin E and vitamin K.
7. Saccharolipids
-fatty acids are linked directly to a sugar
backbone, forming structures that are
compatible with membrane bilayers.

24. Lipid Soluble Vitamins
Vitamin A 800 μg ( upper limit ca. 3000 μg)
Vitamin D 5 to 10 μg ( upper limit ca. 2000
μg)
Vitamin E 15 mg ( upper limit ca. 1 g)
Vitamin K 110 μg ( upper limit not specified)

25. Characteristics of Lipids:
1. Amphiphatic
2. Naturally occcuring
3. Soluble in organic solvents but insoluble
in water.
4. Undergo saponification
5. Undergo emulsification

26. Clinical Significance:
1. Tay-Sachs Disease-infantile form: rapidly
progressing mental retardation,
blindness, early mortality .
2. Gaucher Disease- hepatosplenomegaly,
mental retardation in infantile form, long
bone degeneration.
3. Fabry Disease-kidney failure, skin rashes
4. Fucosidosis-cerebral degeneration,
thickened skin, muscle spasticity

27. 5. Cholera- protein portion of ganglioside.
6. Hypercholesterolemia
- Artherosclerosis
-Coronary Heart Disease
- Diabetes
- Anorexia nervosa

34. 1. Imbalance in the rate of
triacylglycerol formation and
export causes fatty liver.
-Accumulation of lipid as
triacylglycerol in the liver causes
cirrhosis and impaired liver function.

35. Fatty liver falls into two categories:
a. Raised levels of plasma free fatty acids resulting
from mobilization of fat from adipose tissue or
from the hydrolysis of lipoprotein triacylglycerol
by lipoprotein lipase in extrahepatic tissues.
 Increasing amounts of free fatty acids are taken
up by the liver and esterified. The production of
VLDL does not keep pace with the influx of free
fatty acids, allowing triacylglycerol to
accumulate, causing fatty liver.
 During starvation, quantity of triacylglycerol in
the liver is increased, and ability to secret VLDL
is impaired. This may be due to low levels of
insulin.

36. a. Due to a metabolic block in the production of
plasma lipoproteins, thus allowing
triacylglycerol to accumulate.
 Lesion could be due to:
1. A block in apolipoprotein synthesis
2. A block in the synthesis of lipoprotein from
lipid and apolipoprotein
3. A failure in the secretory mechanism
itself.
 In experimental animals, deficiency of
choline, treatment with puromycin,
ethionine, carbon tetrachloride, chloroform,
phosphorous, lead, and arsenic causes fatty
liver.

37. Ethanol also causes fatty liver:
 Alcoholism leads to fat
accumulation in the liver,
hyperlipidemia, and ultimately
cirrhosis

39. A. Increased NADH/NAD+ ratio causes
 Shift in the malate oxaloacetate, which may
reduce activity of the citric acid cycle.
 Net effect of inhibiting fatty acid oxidation is to
cause increased esterification of fatty acids in
triacylglycerol, which may be the cause of fatty
liver.
B. also causes increase in lactate/pyruvate ratio
that results in hyperlacticacidemia, which in
turn decreases the capacity of kidney to
excrete uric acid.
C. Increase in acetyl-CoA causes increased
lipogenesis and cholesterol

41. DAGHANG
SALAMAT!!!