LIPIDS sources and their functional structure.ppt

Describes the lipid sources, their classification and their structure

1. By
Dr George Kazibwe
LIPIDS: STRUCTURE,
FUNCTION & PROPERTIES

2. Define lipids and give some examples.
Give common & systemic names of C6-C20 of
saturated fatty acids.
Classify & list functions of lipids
Explain the role of PUFs in nutrition.
Explain principles of lipid transport:
Lipoproteins
Explain the occurrence & biological functions of
TAGs.
Highlight the metabolism of FAs.
Explain the biosynthesis and roles of bile salts.
Disorders of FA metabolism.

3. These are naturally occurring organic compounds
that are insoluble in water but soluble in organic
solvents.
They are composed of carbon skeleton with
Hydrogen and Oxygen substitutions.
They are hydrophobic in nature because of the
predominance of hydrocarbon chains (-CH
2-
CH
2-

CH
2-) in their structure.
FAs are water insoluble, saturated or unsaturated,
long chain hydrocarbons with a carboxyl group at
the end of the chain.

4. Lipid Primary Function
Fatty acids Energy sources, biosynthetic precursors
Triacylglycerols , TAGsStorage, transport
Phosphoglycerides Membrane components
Ketone bodies Energy sources
Sphingolipids Membrane components
Eicosanoids Modulators of physiological activity
Cholesterol Membrane component
Steroid hormones Modulators of physiological activity

5. Electrical insulators as in myelinated nerves.
Also, facilitate faster conduction of nerve
impulses
Signal transduction, Inositol triphosphate (IP
3)
& diacylglycerol (DAG) are secondary
messengers
Sources of Vit D, bile acids i.e. cholesterol
Thermal insulators

6. Knowledge of lipid biochemistry is vital in
understanding biomedical areas of interest;
Pathogenesis of;
 obesity
 Atherosclerosis
Appreciating the role of polyunsaturated fats
(PUFs) in nutrition and health.

7. Simple lipids- esters of fatty acid with various alcohols
e.g. TAGs- ester of three acyl groups with glycerol.
Complex lipids- esters of fatty acids containing groups
such as phosphate, carbohydrate, proteins e.g.
phospholipids
Derived lipids-Obtained on hydrolysis of simple and
complex lipids e.g. ketone bodies, steroid hormones.

9. A fatty acid is a long, unbranched chain of
hydrocarbons with a carboxyl (COOH) group
at one end.
The carbon atoms are numbered from the
carboxyl atom as number 1.

10. The carbon adjacent to the carboxyl
carbon is 2, 3 , 4 etc.
Also known as α (alpha) β (beta) and, γ
(gamma) carbons respectively.
The terminal methyl carbon is known as
omega (ω) or n-carbon.

11. In nature, there are only two essential fatty
acids.
Linoleic acid and alpha-linolenic acid are
essential fatty acids for mammals.
Becoz: mammals have no enzymes necessary
to introduce a double bond at the omega-3
position or omega-6 position

13. Saturated FAs don’t contain double bonds
They end with the suffix- anoic
Examples, see the table
Numerical symbol Systematic names
10 Decano-
12 Dodecan-
14 Tetradecano-
16 Hexadecano-

14. Contain at least one double bond
They end with the suffix –enoic
e.g.
-enoate one double bond
-dienoate 2“ “
-trienoate 3“ “
-tetraenoate 4“ “

15. Oleic acid 18:1 cis
Δ9
Linoleic acid 18:2 cis
Δ9,12
Linolenic acid 18:3 cis
Δ9,12,15
Arachidonic acid 20:4 cis
Δ5,11, 14,18

16. Fatty acid + glycerol= Fat (an ester)
C(CH2)16CH3
O
HC
H2C
H2CC(CH2)12CH3O
O
O
OC(CH2)16CH3
O

17. Omega system- the reference point is the
last carbon atom farthest from the carboxyl
carbon.
An omega carbon can also be designated as
n-carbon hence n
-9
is equivalent to omega 9.

18. Delta system
•The reference point is the carboxyl carbon
•The site of un-saturation in a fatty acid is
indicated by the symbol delta (Δ
x
) where X
indicates the position of the double bond

20. Cis –hydrogen atoms are on the same side
of the double bond.
Trans-hydrogen atoms are oriented in
opposite directions.
The cis double bond causes a bend in the
molecule, whereas a trans double bond
gives a straight molecule as in a saturated
FA.

21. oComplex molecules used in the formation of
biological membranes.
Composed of glycerol, two fatty acid chains,
and a phosphate group that is also linked to a
small polar group.
A phospholipid is amphipathic, having both
polar and nonpolar regions.

23. 1. Phosphatidylcholine e.g. lecithin
Found in brain, egg yolk, and organ meats
Important in fat metabolism and transport
Used as emulsifying agent in the food industry
2.Phosphatidylethanolamine, e.g. cephalin
Occurs predominantly in nervous tissue
Plays a role in blood clotting
3.Phosphatidylinositol e.g. PIP
2
:
Found in brain, heart, kidneys, and plant tissues
Rapid synthesis and degradation occurs in the brain
Plays role in cell transport processes
Plays role in cell signaling

25. No. of milligrams of KOH required to saponify free &
combined fatty acids in one gram of fat under
specified conditions.
It indicates the molecular weight of a fatty acid.
It also gives a measure of the fatty acid chain length.
Saponification refers to the hydrolysis of fats by alkali
resulting into the formation of glycerol and salts of
fatty acids- soaps.

26. Fats containing short chain fatty acids will have
more carboxylic groups per gram than LCFA
and this will take up more alkali.
Hence, the higher the saponification number,
the shorter the fatty acid chain .
The lower the saponification number, the
longer the fatty acid chain.

27. Is the weight of iodine in grams that adds to
the double bonds of 100 grams of fat.
It measures the degree of unsaturation of a
given fatty acid.
The higher the iodine number, the higher the
degree of unsaturation.