For Nursing Students

1. Biochemistry
for
B.Sc.Nursing
LIPIDS
BRAINSTROMING NOTES TO PRINT
Lipid Reveiw

2.  Lipids (greek: lipos-fat) are of great
importance to the body as the chief
concentrated storage form of energy,
 Besides their role in cellular structure and
various other biochemical functions.
 As such, lipids are a heterogenous group of
compounds and therefore, it is rather
difficult to define them precisely.

3.  Lipids may be regarded as organic substances
relatively insoluble in water, soluble in
organic solvent (alcohol, ether etc) actually
or potentially related to fatty acids and
utilized by the living cells.

4.  Lipids are broadly classified as :
1. Simple Lipids
2. Compound Lipids (Complex Lipids)
a) Phospholipids
i. Glycerophospholipids
ii. Sphingophospholipids
b) Glycolipids
c) Lipoproteins
d) Other complex lipids
3. Derived Lipids
4. Neutral Lipids

5.  Esters of fatty acids with alcohols.
 These are mainly of two types.
 a) Fats & oils (triacylglycerols): these are
esters of fatty acids with glycerol. The
difference between fat and oil is only
physical. Thus, oil is a liquid while fat is a
solid at room temperature.
 b) Waxes: Esters of fatty acids with
alcohols other than glycerol. These
alcohols may be aliphatic or alicyclic. Crtyl
alcohol is most commonly found in waxes.

6.  Esters of fatty acids with alcohols containing additional group
such as phosphate, nitrogenous base, carbohydrates, protein
etc. they are further divided as:
 a) Phospholipids: Lipids containing phosphoric acids and
frequently a nitrogenous base. This is in addition to alcohol
and fatty acids.
 i. Glycerophospholipids: These phospholipids contains glycerol
as the alcohol. E.g. lecithin, cephalin.
 ii. Sphingophospholipids: Sphingosine is the alcohol in this
group of phospholipids e.g. sphingomyelin.
 b) Glycolipids: These lipids contain a fatty acids, carbohydrate
and nitrogenous base. The alcohol is sphingosine, hence they
are also called as glycosphingolipids. Glycerol and phosphate
are absent. E.g. cerebrosides, gangliosides.
 c) Lipoproteins: Macromolecular complex of lipids with
proteins.
 d) Other complex lipids: Sulfolipids, aminolipids &
lipopolysaccharides.

7.  These are the derivative obtained on the
hydrolysis of group I and group 2 lipids
which possess the characteristic of lipids.
These include glycerol and other alcohols,
fatty acids, mono- and diacylglycerols,
lipids soluble vitamins, steroids hormones,
hydrocarbons and ketone bodies.
Miscellaneous: These include a large
number of compounds possessing the
characteristic of lipids e.g. caratenoids,
squalene, hydrocarbons such as
pentacosane, terpenes etc.

8.  These lipids which are uncharged are
referred to as neutral lipids. These are
mono-, di-, and triacylglycerols,
cholesterol and cholesteryl esters.

9. i. Are the concentrated fuel reserve of the
body.
ii. Are the constituents of membrane structure
and regulates the membrane permeability.
iii. Serve are sources of fat soluble vitamins
(K,E,D & A).
iv. Are important as cellular metabolic
regulators (steroids hormones &
prostaglandins).
v. Protects the internal organs, serve as
insulating materials and give shape and
smooth appearance to the body.

10.  Daily consumption of the lipid:
 In Developed Country is 60-150 gram/day
 Poorer Section of Society <60 gram/day
 In lipid diet around 90% is fat (triacylglycerol).
 Remaining is made up of phospholipid, cholesterol, chlesteryl
esters and free fatty acids.
 In addition about 1-2 gram cholesterol and 3-5 gram
phospholipids are secreted into the intestine by bile.
 Lipids are insoluble or sparingly soluble in aqueous solution.
 The digestive enzymes, however are present in aqueous
medium.
 This posses certain problem for the digestion and absorption
of lipids.
 Fortunately, the digestive tract possesses specialized
machinery to
 a) Increase the surface area of lipids for digestion.
 b) Solubilize the digestive products for absorption.
Cont….

11.  In adult:
 Digestion of lipid is initiated in the stomach,
catalysed by lingual lipase and gastric lipase
which can degrade fat containing short chain
fatty acids at neutral pH.
 Digestion of lipid in stomach is negligible in
adult.
 In Infant:
 Milk fat (with short chain fatty acids) can be
hydrolysed by gastric lipase to some extent
because of stomach pH of infant is close to
neutrality, i.e. ideal for gastric lipase action.
Cont….

12.  Emulsification is the phenomenon of
dispersion of lipids into smaller droplets
due to reduction on the surface tension.
 The process of emulsification occurs by
three complementary mechanism:
a) Detergent action of bile salts.
b) Surfactant action of degraded lipids.
c) Mechanical mixing due to peristalsis.
Cont….

13.  Bile salt is the most effective emulsifying
agents.
 They interact with lipids particles and the
aqueous duodenal contents and convert
them into smaller particles.
 Further bile salt stabilize the smaller
particles by preventing them from merging.
Cont….

14.  The initial digestive products of lipids
namely free fatty acids, monoacylglycerols
promote emulsification.
 These compounds along with phospholipids
are known as surfactants.
 Surfactant gets absorbed to the water
lipids interfaces and increases the
interfacial area of lipid droplets.
 Thus the initial action of the enzyme lipase
helps in further digestion of the lipids.
Cont….

15.  Mechanical mixing due to peristalsis also
helps in the emulsification of the lipids.
 The smaller lipids emulsion droplets are
good substrates for digestion.
Cont….

16.  The pancreatic enzymes are primarily
responsible for the degradation of dietary
triacylglycerols, cholesteryl esters and
phospholipids.
Triglycerols
2-monoacylglycerol + Free fatty acids

17. Thank You