34 What Are Lipids Lipids are a diverse group of molecules that contain regions composed almost entirely of hydrogen and carbon All lipids contain large chains of nonpolar hydrocarbons Most lipids are therefore hydrophobic and water insoluble ID: 441499
Download Presentation The PPT/PDF document "LIPIDS" 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
LIPIDSSlide2
3.4 What Are Lipids?
Lipids
are a diverse group of molecules that contain regions composed almost entirely of hydrogen and carbon
All lipids contain large chains of nonpolar hydrocarbons
Most lipids are therefore hydrophobic and water insolubleSlide3
Animation: LipidsSlide4
3.4 What Are Lipids?
Lipids are diverse in structure and serve a variety of functions
They are used for energy storage
They form waterproof coverings on plant and animal bodies
They serve as the primary component of cellular membranesStill others are hormonesSlide5
3.4 What Are Lipids?
Lipids are classified into three major groups
Oils, fats, and waxes
Phospholipids
Steroids containing rings of carbon, hydrogen, and oxygenSlide6
3.4 What Are Lipids?
Oils, fats, and waxes are lipids containing only carbon, hydrogen, and oxygen
Oils, fats, and waxes are made of one or more
fatty acid
subunitsSlide7
3.4 What Are Lipids?
Oils, fats, and waxes are lipids containing only carbon, hydrogen, and oxygen
(continued)
Fats
and oils Are used primarily as energy-storage molecules, containing twice as many calories per gram as carbohydrates and proteinsAre formed by dehydration synthesisThree fatty acids glycerol triglycerideSlide8
Figure 3-12 Synthesis of a triglyceride
triglyceride
fatty acids
glycerol Slide9
Figure 3-13a Fat
Fat Slide10
3.4 What Are Lipids?
Oils, fats, and waxes are lipids containing only carbon, hydrogen, and oxygen
(continued)
Fats that are solid at room temperature are
saturated (the carbon chain has as many hydrogen atoms as possible, and mostly or all C–C bonds); for example, beef fatSlide11
Figure 3-14a A fat
A fat Slide12
3.4 What Are Lipids?
Oils, fats, and waxes are lipids containing only carbon, hydrogen, and oxygen
(continued)
Fats that are liquid at room temperature are
unsaturated (with fewer hydrogen atoms, and many CC bonds); for example, corn oilUnsaturated trans fats have been linked to heart diseaseSlide13
Figure 3-14b An oil
An oilSlide14
3.4 What Are Lipids?
Oils, fats, and waxes are lipids containing only carbon, hydrogen, and oxygen
(continued)
Waxes are highly saturated and solid at room temperature
Waxes form waterproof coatings such as onLeaves and stems in plantsFur in mammalsInsect exoskeletonsWaxes are also used to build honeycomb structuresSlide15
Figure 3-13b Wax
Wax Slide16
3.4 What Are Lipids?
Phospholipids have water-soluble “heads” and water-insoluble “tails”
These form plasma membranes around all cells
Phospholipids consist of two fatty acids
glycerol
a short polar functional groupThey have hydrophobic and hydrophilic portionsThe polar functional groups form the “head” and are water soluble
The nonpolar fatty acids form the “tails” and are water insolubleSlide17
Figure 3-15 Phospholipids
fatty acid tails
phosphate
group
variable
functional
group
glycerol
backbone
polar head
(hydrophilic)
(hydrophobic)Slide18
3.4 What Are Lipids?
Steroids contain four fused carbon rings
Steroids
are composed of four carbon rings fused together with various functional groups protruding from them
Examples of steroids include cholesterolFound in the membranes of animal cellsComponent of male and female sex hormonesMakes up 2% of human brainExcessive cholesterol contributes to cardiovascular diseaseSlide19
Figure 3-16 Steroids
Estrogen
Testosterone
Cholesterol Slide20
Building
Triglycerides and OlestraSlide21
TriglycerideSlide22
Olestra
Olestra is a large water insoluble sucrose polyester made of 6-8 fatty acids
bonded
to sucrose. The type and number of fatty acids determine the physical properties of Olestra
The fatty acids come from edible oils such as cottonseed, corn, and soybean oilsSlide23
Olestra is a food ingredient which is chemically
prepared
with
similar properties of fats
.Olestra is a fat-substitute will sucrose backbone. As it is not absorbed, its calorific value is zero.They are not absorbed in the intestines. This is due to their large size.A
tri-ester of fatty acid can be easily absorbed but a polymer of 6-8 fatty acids with a sucrose molecule as backbone is a large compound impossible to absorbed and metabolized
.This
fat substitute is stable at higher temperatures also. It has zero saturated and trans fat but tastes like fat.However, there are problems with this chemically synthesized compound too.Many cases with digestive upset were observed as this molecule will directly excreted in stools because it is not absorbed in intestines. Also, vitamin and phyto-chemical losses occur.
Olestra
was produced by Olean company.Slide24
olestraSlide25