1 Lipids Lipids commonly referred to as fats a re substances of biological origin Soluble in organic solvents such as chloroform and methanol Fats oils certain vitamins and hormones and most non protein membrane components are lipids ID: 917761
Download Presentation The PPT/PDF document "Lipids Bioc . 201 بسم الله الر..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Lipids
Bioc. 201
بسم الله الرحمن الرحيم
1
Slide2Lipids
Lipids, commonly referred to as fats, are substances of biological origin.
Soluble in organic solvents such as chloroform and methanol. Fats, oils, certain vitamins and hormones, and most non protein membrane components are lipids.2
Slide3Functions of Lipids
Lipids play three major roles in human biochemistry:
Store energy within fat cells. Because they are composed of mostly carbon-hydrogen (C—H) bonds, they are a rich source of energy and an efficient way for the body to store excess calories.Parts of membranes that separate compartments of aqueous solutions from each other. Because of their unique physical properties, lipids are also an integral part of cell membranes and, therefore, also play an important structural role in cells.
Serve as chemical messengers such as steroid hormones.
3
Slide4Lipids Classification
The major classes of lipids are:
Fatty acids.
Triglycerols
.
Glycerphospholipids
.
Sphingolipids
.
Steroids.
4
Slide5Lipids Classification
5
Slide6Fatty Acids
6
Slide7Fatty Acids
Fatty acids are simply linear long-chains of C—H bonds that terminate with a carboxyl group (—COOH).
Composed of a carboxylic acid “head group” and a long hydrocarbon “tail”.
7
Slide8Fatty Acids
Fatty acids are variable in length and can be classified as:
Short-chain (4-6 carbon atoms) fatty acids.Medium-chain (8-12 carbon atoms) fatty acids.Long-chain
(more than 12
carbon atoms
)
fatty acids.
8
Slide9Fatty Acids
Most fatty acids in our diet are of the long-chain variety and contain an even
number of carbon atoms.In higher plant and animals, the predominant fatty acid residues are those of the C16 and C18
species
palmitic
, oleic,
linoleic
, and
steric
acids.
Fatty acids with <14 or >20 carbon atoms are uncommon.
9
Structural formula of some C
18
fatty acids. The double bonds all have the
cis
conformation.
Slide10Fatty Acids
Not all of the carbon atoms on fatty acids are fully saturated or bonded with hydrogen atoms: some of them may instead form carbon=carbon (C=C) double bond.
Depending on the number of C=C double- bonds, fatty acids can be classified as:Saturated (no double-bonds).Unsaturated (contain double bonds). Polyunsaturated
(two or more double-bonds).
Over half of the fatty acid residues of plant and animal lipids are unsaturated and polyunsaturated
.
10
Slide11Fatty Acids
11
Saturated Fatty Acids:
Octanoic
Acid
Unsaturated Fatty Acids:
3 -
Octenoic
Acid
3, 6 -
Octadienoic
Acid
Short hand: 8:1 (
Δ
3
)
8:2 (
Δ
3,6
)
Slide12Fatty Acids
12
Cis 9 - Octadecenoic Acid (oleic)
Trans 9 - Octadecenoic Acid (elaidic acid)
Cis
And Trans Fatty Acids:
Slide13Fatty Acids
13
Linoleic
acid:
Cis
,
cis
, 9, 12 -
Octadecadienoic
acid
Linolenic
acid:
Cis
,
cis
,
cis
9, 12, 15 -
Octadecatrienoic
acid
Arachidonic
acid:
Cis
,
cis
,
cis
,
cis
5, 8, 11, 14 -
Eicosatetraenoic
acid
Linoleic
Acid
Linolenic
Acid
Arachidonic
Acid
Slide14Fatty Acids
The first double bond of an unsaturated fatty acid commonly occurs between its C9 and C10
atoms counting from the carboxyl C atom (a Δ9- or 9-double bond).Triple bonds rarely occur in fatty acids or any other compound of biological origin.
14
Slide15Fatty Acids
15
Slide16Fatty Acids
Cis
and trans configuration:The C=C double-bonds of unsaturated fatty acids are typically arranged in the cis form, with both hydrogen atoms on the same side of the C=C double-bonds, which causes a bend in their structure. Fatty acid C=C double-bonds can also occur in the trans configuration, with both hydrogen atoms on opposite side of the C=C double-bond.
16
Slide17Fatty Acids
Cis
and trans configuration:17
Slide18Fatty Acids
Cis
and trans configuration:Fatty acid double bonds almost always have the cis configuration. The trans fatty acids are not commonly in nature; however, they are present in our diet because the chemical hydrogenation treatment used in food processing for converting polyunsaturated plant oils into margarine introduces trans double bonds.
18
Slide19Fatty Acids
In plasma, only a relatively small amount of fatty acids exists in the free or unesterified form.
The majority of plasma fatty acids are found as a constituent of triglycerides or phospholipids.Fatty acids are covalently attached to the glycerol backbone of triglycerides and phospholipids by an ester bond
that forms between the carboxyl group (CO) on the fatty acid and the hydroxyl group (OH)on glycerol.
19
Slide20Simple Lipids: Triglycerides
20
Slide21Triglycerides
Triglycerides
(also referred to as Triacylglycerols or neutral fats
).
contain
three fatty acid molecules
attached to
one molecule of glycerol
by
ester bonds
.
Each fatty acid in the triglyceride molecules can potentially by different in structure, thus producing many possible structural forms of triglycerides.
Fats
and
oil
that occur in
plants
and
animals
consist largely of mixtures of
Triglycerides.
21
Slide22Triglycerides
Triglycerides have no charged or polar hydrophilic groups, making them very hydrophobic and virtually water insoluble.
The hydrophobic character of triglycerides is caused by the long hydrocarbon chains. Because it has no charge, triglyceride is classified as neutral lipid.
22
Slide23Triglycerides
Triglycerides are the most common lipid materials, although mono and
diglycerides are not infrequent. In mono- and di- types, only one or two -OH groups of the glycerol are esterified by fatty acids.1 Fatty Acid + Glycerol = monoacylglycerol
2 Fatty Acids + Glycerol =
diacylglycerol
3 Fatty Acids + Glycerol =
triacylglycerol
23
Slide24Triglycerides
Triacylglycerols
differ according to the identity and placement of their three fatty acid residues: 1. Simple
triacylglycerols
contain
one
type of fatty acid residue and are named accordingly. For example:
Tristearoylglycerol
or
tristearin
contains three
stearic
acid residues.
2. Mixed
triacylglycerols
contain
two
or
three
different types of fatty acid residues and are named according to their placement on the glycerol moiety.
24
Slide25Triglycerides
Oils and Fats:
Oils: most triglycerides from plant sources, such as corn and sunflower seeds, are rich in polyunsaturated fatty acids and are oils (liquid at room temperature).Fats: triglycerides from
animal sources
contain mostly
saturated
fatty acids and are usually
solid
at room temperature.
25
Slide26Pure Fats
Pure fats and oils are
colorless, odorless, and tasteless. This statement may seem surprising because we all know the tastes and colors
of such fats and oils as butter, and olive oil. The tastes,
odors
, and
colors
are caused by small amounts of other substances dissolved in the fat or oil.
26
Slide27Triglycerides
are efficient energy reserves
Fats are highly efficient form in which to store metabolic energy because:Fats are less oxidized than are carbohydrates
or
proteins
and hence
yield
significantly
more energy on oxidation.
Fats
, being
non polar
substances,
are stored in anhydrous form,
whereas glycogen bind about twice its weight of water. Fats
therefore
provide
about
six times
t
he
metabolic energy
of an equal weight of
hydrates
glycogen
.
27
Slide28Adipocytes
(fat cells)
Adipocytes (fat cells) are specialized for the synthesis and storage of triacylglycerols in animals.
Adipose tissue
is most abundant in a subcutaneous layer and in the abdominal cavity.
28
Slide29Adipocytes
(fat cells)
Functions:Fat
content of normal human (21% for men, 26% for women) enables them to survive starvation for 2 to 3 months. In contrast, the body’s
glycogen
supply, which functions are a short-term energy store, can provide for the body’s metabolic need for less than a day.
The subcutaneous fat layer also provides thermal insulation.
29
Slide30Saponification (Soap making)
Saponification
is a process by which triglycerides are reacted with sodium or potassium hydroxide to produce glycerol and a fatty acid salt, called 'soap'. Lipids that contain fatty acid ester linkages can undergo hydrolysis. This reaction is catalyzed by a strong acid or base. Saponification is the alkaline hydrolysis of the fatty acid esters.
30