第二章 脂质化学 - Gadjah Mada University

Report
LIPIDS
by Endang Astuti
Chemistry Department
Lipids can be considered to be biological molecules
which are soluble in organic solvents, such as
chloroform/methanol and are sparingly soluble in
aqueous) solutions.
Their are three major classes of lipids:
Triglyserides
Phospholipids
steroids
Lipid functions
Energy storage
•Fates stored in adipose tissue
Cell membrane structure
•Creates a barrier for the cell.
•Controls flow of materials.
Hormones and Vitamins
•Hormones-communication between cells.
•Vitamins-assist in the regulation of biological processes.
1. Structure of fatty acids
Fatty acids have a long hydrocarbon chain with a
terminal carboxylic acid group. Most of fatty acids
have an even number of carbon atoms in an
unbranched chain.
Saturated fatty acids have no-double bonds between
the carbon atoms, whereas mono- and polyunsaturated
fatty acids have one or more double bonds.
The properties of a fatty acid depend on the chain
length and the number of double bonds.
Stearic acid
Fatty acids are long unbranched
Oleic acid
chains of carbon atoms.
A carboxyl (-COOH) group at one end
gives the molecule its acidic properties.
Most naturally occurring fatty acids
contain an even number of carbon
atoms in their backbone chains.
Although a few with odd numbers are
found in all organisms, these make up
only a minor fraction of the total.
COMMON BIOLOGICAL SATURATED FATTY ACIDS
Symbol
common name
12:0
Lauric acid
systematic name
dodecanoic acid
structure
mp(℃)
CH3(CH2)10COOH
44.2
14:0
Myristic acid tetradecanoic acid
CH3(CH2)12COOH
52.0
16:0
Palmitic acid Hexadecanoic acid
CH3(CH2)14COOH
63.1
18:0
Stearic acid
CH3(CH2)16COOH
69.6
CH3(CH2)18COOH
75.4
20:0
Octadecanoic acid
Arachidic aicd Eicosanoic acid
COMMON BIOLOGICAL UNSATURATED FATTY ACIDS
Symbol
16:1D9
18:1D9
18:2D9,12
common name
systematic name
Palmitoleic acid Hexadecenoic acid
Oleic acid
9-Octadecenoic acid
Linoleic acid 9,12 -Octadecadienoic acid
structure
mp
CH3(CH2)5CH=CH-(CH2)7COOH
-0.5
CH3(CH2)7CH=CH-(CH2)7COOH
13.4
CH3(CH2)4(CH=CHCH2)2(CH2)6COOH
18:3D9,12,15 a-Linolenic acid9,12,15 -Octadecatrienoic acidCH3CH2(CH=CHCH2)3(CH2)6COOH
-9
-17
Reaction of fatty acid
2. triglyceride
Ester of glycerol and a fatty acid.
Principal functions is energy storage-fat.
May have 1-3 fatty acids which can each be different.
1-monoglycerid 2-diglyceride 3-triglycerid
Examples of triglyceride
O
CH2OH
O
CHOH + (R1,R2,R3 ) C OH
CH2OH
O
H2C O C R1
R2 C O
CH
O
H2C O C R3
+ 3H2O
Sucrose Polyester, SPE
Physical Properties of glyceride
Solubility
Generally, triglycerides are completely nonpolar,
with no affinity for water. But, since bi- or monoglyceride consist of a polar or hydrophilic head
and one or two nonpolar or hydrophobic tails ,
they are called amphiphilic and can be used as
emulsifier.
Melting Point
Depending on chain length and number of
double bond .
Chemical Properties of triglyceride
1. Saponification
Saponification Number The number of milligrams of
KOH required to saponify 1g of fat; an approximate
measure of the average molecular weight of a fat.
2. Alcoholysis
H2COOCR
CH2OH
¼î ÐÔ´ ß»¯¼Á
HCOOCR'+3CH3OH
R(R',R'')COOCH3+ CHOH
H2COOCR''
CH2OH
3. hydrolysis
O
CH2OH
O
CHOH + (R1,R2,R3 ) C OH
CH2OH
O
H2C O C R1
R2 C O
CH
O
H2C O C R3
+ 3H2O
4. Halogenation or hydrogenation
Iodine number
5. Rancidity
Acid number
3 Phosphoglycerides
Lipids that contain a phosphate group.
Modified fat
Phosphate replaces on fatty acid chain.
Uses
Production of cell membranes.
Emulsifying agents.
CH2OH
CH 2OH
1
HO
HO
C
H
2
CH 2OH
Á¢Ìå רһ±àºÅ
C
H
O
H2C
O
P
3
O£-
O£-
Phospho-glycerol
Stereospecific numbering
O
O
O
R2
C
O
H2C
O
C
C
H
O
H2C
O
P
O
phosphatidic acid
O
R1
R2
O
C
O
H2C
O
C
C
H
O
H2C
O
P
R1
£-
£-
O
O
£-
Phosphoglycerides
X
Nonglycerol lipids
Sphingolipids Example
Sphingomyelin
Glycosphingolipids
4. sterols
12
11
13
17
14
1
9
2
10
3
5
4
6
16
15
8
7
Cyclopentane Phenanthrene Cyclopentanoperhy
dro-phenanthrene
Cholesterol
Cholesterol is a waxy, fat-like compound that
belongs to a class of molecules called steroids. It's
found in many foods, in your bloodstream and in all
your body's cells. If you had a handful of cholesterol,
it might feel like a soft, melted candle. Cholesterol is
essential for:




Formation and maintenance of cell membranes (helps the
cell to resist changes in temperature and protects and
insulates nerve fibers)
Formation of sex hormones (progesterone, estradiol ,
testosterone)
Production of bile salts, which help to digest food
Conversion into vitamin D in the skin when exposed to
sunlight.
•The formation of cholesterol
involves a series of
complicated biochemical
reactions that begin with the
widespread 2-carbon molecule
Acetyl CoA.
•Cholesterol is made primarily
in your liver (about 1,000
milligrams a day), but it is also
created by cells lining the
small intestine and by
individual cells in the body.
Most of the body's cholesterol is manufactured in the liver.
•When your doctor takes a blood test to
measure your cholesterol level, the doctor is
actually measuring the amount of circulating
cholesterol in your blood, or your blood
cholesterol level.
•About 85 percent of your blood cholesterol
level is endogenous , which means it is
produced by your body. The other 15 percent
or so comes from an external source -- your
diet.
• Your dietary cholesterol originates from
meat, poultry, fish, seafood and dairy
products. It's possible for some people to eat
foods high in cholesterol and still have low
blood cholesterol levels. Likewise, it's
possible to eat foods low in cholesterol and
have a high blood cholesterol level.
This coronary artery is becoming
dangerously blocked as the
cholesterol builds up.
21
18
20
19
11
12
13
14
1
2
3
HO
10
4
5
9
6
17
16
15
22
23
24
8
7
25
26
Structure of cholesterol
27
Phytosterols
(dari tanaman)
21
21
18
18
20
19
11
12
13
14
1
9
2
10
3
5
4
6
17
16
15
20
22
19
23
11
1
2
7
3
9
10
5
4
6
8
7
HO
Stigmasterol
13
14
24
8
HO
12
Glusterol
17
16
15
22
23
24
steroid
vitamin E
(tocopherol)
•As an anti-oxidant that assists in protecting cellular and subcellular
membranes in the body.
•Helping the body's immune system.
•May slow down premature aging by way of its protective effects
from free radicals caused by environmental factors.
•May prevent cancer growth.
•May lower blood sugar levels in diabetic patients
•Inhibits platelet formation that are associated with atherosclerosis.
Only a relatively small amount of vitamin E is required to meet normal daily
requirements. Fortunately, this amount is easily obtained from foods such as
oill, many grains, nuts, and fruits, as well as fatty parts of meats.
5. Biomembrane
 It must keep its molecules of life ( DNA , RNA ,
and its assortment of proteins ) from dissipating
away.
 It must keep out foreign molecules that damage
or destroy the cells components and molecules.
Composition of biomembrane
Lipids



phospholipids
cholesterol
Glycosphingolipids
Protein


intrinsic protein
extrinsic protein
Others

saccharide and ions
Biological membranes
EXTERIOR OF CELL
CARBOHYDRATE
INTEGRAL PROTEIN
LIPID BILAYER
PERIPHERAL PROTEIN
CYTOPLASM SIDE
The Fluid Mosaic Model
Lipid bilayers are fluid, and individual
phospholipids diffuse rapidly throughout
the two dimensional surface of the
membrane;
Membrane proteins diffuse throughout
the membrane in the same fashion.
The Fluid Mosaic Model
侧向移动
旋转
摆动
翻转
To "flip-flop" through the membrane to the opposite
side is uncommon. To do so required the hydrophilic
head of the phospholipid to pass fully through the
highly hydrophobic interior of the membrane, and for
the hydrophobic tails to be exposed to the aqueous
environment.
Factors Influencing Fluidity of Biological
Membrane
the ratio of saturated to unsaturated
hydrocarbon chains of the phospholipids;
level of cholesterol in the cell membrane;
Other factors such as ionic strength, polar
group of phospholipids.
Membrane Transport Mechanisms
Simple Diffusion
Diffusion is always
down a concentration
gradient.
Facilitated Diffusion
Active Transport
Active transport
requires the
expenditure of energy.
The Na+-glucose Co-transporting Mechanism
Na+-K+-ATP酶
Epithelial Cells are Joined Together

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