Biochemistry stuff

1. MODULE 2.1: Demonstrating the
Nature and Functions of
Biomolecules
LIPIDS
Prepared by:
ARJADE O. ALCABAZA, LPT
Biochemistry Instructor

2. LEARNING OUTCOME/S:
At the end of the lesson, the students will be
able to:
 Demonstrate the nature and function of
biomolecules: lipids.

3. Topic Outline
LIPIDS (Structure and Classifications)
FATTY ACIDS (Classifications, Physical and Chemical Properties)
ENERGY-STORAGE LIPIDS
DIETARY CONSIDERATIONS
CHEMICAL REACTIONS OF TRIACYLGLYCEROLS
MEMBRANE LIPIDS
EMULSIFICATION LIPIDS
MESSENGER LIPIDS
PROTECTIVE-COATING LIPIDS
TRANSPORT LIPIDS

4. STRUCTURE AND CLASSIFICATION OF
LIPIDS
Lipids
An organic compound found in living organisms that is
insoluble (or only sparingly soluble) in water but soluble in
non-polar organic solvents.
Unlike biomolecules, lipids do not have a common structural
features that serves as the basis for defining compounds.

5. STRUCTURE AND CLASSIFICATION OF
LIPIDS
Lipids are classified based on two methods:
 Biochemical function
 Saponification

6. Classification based on
Biochemical Function:
For purposes of simplicity
of study of lipids are divided into
five categories based on their
biochemical function:
Energy-Storage Lipids – Ex.
Triacylglycerols
Membrane Lipids – Ex. Phospholipids,
Sphingoglycolipids, and cholesterols
Emulsification Lipids – Ex. Bile acids
Chemical Messenger Lipids – Ex.
Steroid hormones and eicosanoids
Protective-Coating Lipids – Ex.
Biological waxes
Transport Lipids – Ex. Lipoproteins
STRUCTURE AND
CLASSIFICATION OF
LIPIDS

7. Classification based on
Saponification:
Saponification reaction
refers to a hydrolysis reaction
that occurs in a basic solution.
Based on saponification, lipids
are divided into two categories:
Saponifiable Lipids –
Ex. Triacylglycerols,
phospholipids,
sphingoglycolipids, and
biological waxes
Non-saponifiable
Lipids – Ex. Bile acids,
Steroid hormones,
eicosanoids, and
cholesterol
STRUCTURE AND
CLASSIFICATION OF
LIPIDS

8. STRUCTURE AND
CLASSIFICATION OF LIPIDS
Structure
• Lipids exhibit structural
diversity.
• Some are esters, some are
amides, and some are
alcohols (acyclic and cyclic)
and some are polycyclic.

9. https://i1.wp.com/www.differencebetween.com/wp-content/uploads/2022/07/Fatty-
Acid.png?resize=768%2C672&ssl=1
Fatty
Acids

10. FATTY ACIDS
A fatty acid is the
building block of fats in
nature. In biochemistry, a
fatty acid is defined as a
carboxylic acid with an
aliphatic (hydrocarbon)
chain.
https://library.med.utah.edu/NetBiochem/mml/fa_polypatt01.gif

11. FATTY ACIDS
Fatty acids are one of the major components of lipids. Fatty
acids and glycerol combine together to form lipids. Fatty acids are
classified in numerous ways such as:
 by length (short chain, medium chain, long chain, or very long chain)
 by saturation vs. unsaturation
 by linear vs. branched chain
 by their ability or inability to be synthesized by animals

12. CLASSIFICATION OF
FATTY ACIDS
By Number of Carbon Atoms
 Long chain fatty acids – 12 to
26 carbon atoms
 Medium chain fatty acids – 6
to 11 carbon atoms
 Short chain fatty acids – 4 to 5
carbon atoms
https://www.researchgate.net/profile/Shilpa-Shetty-
7/publication/354944913/figure/fig1/AS:1074178916642817@1633115619773/Sources-of-fatty-acid-
and-examples-of-medium-chain-fatty-acids-C6-C8-C10-and-C12.png

13. CLASSIFICATION OF
FATTY ACIDS
By degree of saturation
 Saturated Fatty Acids – all
carbon-carbon are single
bonds.
 Unsaturated Fatty Acids
 Monounsaturated – one double bond is
present
 Polyunsaturated – more than one double
bond is present.
https://cdn1.byjus.com/wp-content/uploads/2022/03/word-image101.png

14. https://docbrown.info/page06/addhoc06/transfat4.gif

15. TYPES OF FATTY ACIDS
A. SATURATED FATTY ACIDS
 Fatty acid with a carbon chain in which all C—C bonds are single bonds
STRUCTURAL NOTATION
 It indicates the number of carbon atoms
 Numbering WILL ALWAYS STARTS at the –COOH group or part of the fatty acid
 Ex. Lauric acid has 12 carbon atoms
and no double bonds so its
structural notation is (12:0)

16. TYPES OF FATTY ACIDS
B. UNSATURATED FATTY
ACIDS
1) Monosaturated Fatty Acids
– is a fatty acid with ONE
carbon-carbon double bond
is present.
Ex. Oleic Acid (18: 1∆9
)

17. TYPES OF FATTY ACIDS
B. UNSATURATED FATTY
ACIDS
1) Monosaturated Fatty Acids
– is a fatty acid with ONE
carbon-carbon double bond
is present.
Ex. Oleic Acid (18: 1∆9
) This means that the
double bond starts at
carbon number 9 starting
from –COOH part.

18. To specify double-bond positioning within the carbon chain
of an unsaturated fatty acid, the preceding notation is expanded
by adding the Greek capital letter delta (∆) followed by one or
more superscript numbers. The notation 18: 3∆9,12,15
denotes a
𝐶18 PUFA (Polyunsaturated Fatty Acid) with three double bonds at
locations between carbons 9 and 10, 12 and 13, and 15 and 16.

19. TYPES OF FATTY ACIDS
B. UNSATURATED
FATTY ACIDS
2) Polysaturated Fatty
Acids (PUFA) – is a
fatty acid with
MORE THAN ONE
carbon-carbon
double bond is
present.

20. UNSATURATED FATTY ACIDS AND
DOUBLE-BOND POSITION
Several different “families” of unsaturated fatty acids exist. It
depends on when a double-bond position is specified relative to the
methyl (noncarboxyl) end of the fatty acid carbon chain. Double-bond
positioning is denoted by using the Greek lower-case letter omega
(𝝎).
Two types of unsaturated fatty acids:
Omega-3 Fatty Acids
Omega-6 Faty Acids

21. UNSATURATED FATTY ACIDS AND
DOUBLE-BOND POSITION
A. Omega-3 Fatty Acids (𝜔 − 3) – an unsaturated fatty acid with its
endmost double bond is three carbon atoms away from its methyl
end.
20: 5∆5,8,11,14,17

22. UNSATURATED FATTY ACIDS AND
DOUBLE-BOND POSITION
B. Omega-6 Fatty
Acids (𝜔 − 6) – an
unsaturated fatty
acid with its
endmost double
bond is six carbon
atoms away from its
methyl end.

24. PHYSICAL AND
CHEMICAL PROPERTIES
OF FATTY
ACIDS 

25. PHYSICAL PROPERTIES OF FATTY
ACIDS
A. WATER SOLUBILITY:
Solubility decreases as carbon chain length increases.
 Short-chain Fatty Acids – have a slight solubility in water.
 Long-chain Fatty Acids – are essentially insoluble in water.
Ex.
At 30°C, lauric acid (12:0) has a water solubility of 0.063 g/L and
stearic acid (18:0) has a water solubility of 0.0034 g/L.

26. PHYSICAL PROPERTIES
OF FATTY ACIDS
B. MELTING POINT:
The melting point of a
fatty acid depends on the
length of the carbon chain and
on the number of double bonds
present in the carbon chain.

27. CHEMICAL PROPERTIES
OF FATTY ACIDS
SPACE-FILLING MOLECULES
The number of bends in a
fatty acid chain increases as the
number of double bonds
increases.
 Less packing occurs
 Melting point is lower
 Tend to be liquids at room
temperature
These “bends” prevent unsaturated fatty acids from
packing together as tightly as saturated fatty acids.
The greater the number of double bonds, the less
efficient the packing.

28. ENERGY-STORAGE
LIPIDS:
TRIACYLGLYCEROLS

29. ENERGY-STORAGE LIPIDS:
TRIACYLGLYCEROLS
TRIACYLGLYCEROLS
 Function as energy storage in the body and is much more efficient at
storing energy than glycogen because large quantities of them can be
packed into a very small volume.
 It is primarily concentrated in adipocytes (can be found in adipose
tissue)
 It is the most abundant type of lipid present in the human body.

30. https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTb2mLQTxy73CTaNTH--OUopuhSC1gWWLoMdTMj6HFnPXZEnhmCNH-1lwaWRmrcf0V45S4&usqp=CAU
https://us.123rf.com/450wm/magone/magone1511/magone151100054/49170158-fresh-raw-meat-background-macro.jpg?ver=6
Adipocytes are nearly filled with
triacylglycerols.

31. ENERGY-STORAGE LIPIDS:
TRIACYLGLYCEROLS
Formally defined, a triacylglycerol is a
lipid formed by esterification of three fatty
acids to a glycerol molecule.
Within the name triacylglycerol is the
term acyl. An acyl group is the portion of a
carboxylic acid that remains after the —OH
group is removed from the carboxyl carbon
atom.

32. ENERGY
-STORAGE
LIPIDS:
TRIACYLGLYCEROLS
In the formation of the
triacylglycerol, three
molecules of water have
been removed from the
structural components of the
triacylglycerol, leaving 3 fatty
acid residues and a glycerol
residue. An older name that
is still frequently used for
triacylglycerol is triglyceride.

33. ENERGY-STORAGE LIPIDS:
TRIACYLGLYCEROLS
TWO TYPES OF TRIACYLGLYCEROLS
 Simple Triacylglycerols – three identical fatty acids are
esterified. Naturally occurring simple triacylglycerols are rare
 Mixed Triacylglycerols – triester formed from the esterification
of glycerol with more than one kind of fatty acid.

34. ENERGY
-STORAGE
LIPIDS:
TRIACYLGLYCEROLS
SIMPLE TRIACYLGLYCEROL
Structure of the simple
triacylglycerol produced
from the triple esterification
reaction between glycerol
and three molecules of
stearic acid (18:0 acid).
Three molecules of water
is a by-product of this
reaction.

35. ENERGY
-STORAGE
LIPIDS:
TRIACYLGLYCEROLS
MIXED TRIACYLGLYCEROL
Structure of a mixed
triacylglycerol in which
three different fatty acid
residues are present.

36. ENERGY-STORAGE LIPIDS:
TRIACYLGLYCEROLS
FATS AND OILS
FATS
 is a triacylglycerol mixture that is a solid or semi-solid at room temperature
 fats are obtained from animal sources
 Predominantly saturated
OILS
 is a triacylglycerol mixture that is a liquid at room temperature
 oils are obtained from plant sources
 Predominantly unsaturated

37. FATS AND OILS
FATS
 are composed predominantly of saturated fatty
acids predominate,
 can pack closely together because of the
“linearity” of their fatty acid chains causing the
higher melting points.
OILS
 Are composed of larger amounts of mono- and
polyunsaturated fatty acids than those in fats.
 cannot pack as tightly together because of
“bends” in their fatty acid chains resulting in
lower melting points.
https://med.libretexts.org/Bookshelves/Nutrition/Realities_of_Nutrition_%28Morrill%29/05%3A_Fats
Mysteries_and_Simplicities/08%3A_Fats_Seen_and_Unseen/8.03%3A_What_is_a_Fat

38. PROPERTIES OF FATS
AND OILS
Pure fats and pure oils are
colorless, odorless, and tasteless. The
tastes, odors, and colors associated
with dietary plant oils are caused by
small amounts of other naturally
occurring substances present in the
plant that have been carried along
during processing. The presence of
these “other” compounds is usually
considered desirable.

39. DIETARY
CONSIDERATIONS
AND THE
TRIACYLGLYCEROLS

40. A. GOOD FATS VS. BAD FATS
Studies indicate that the type of dietary fat and amount of
dietary fats are important for a balanced diet. The current
recommended amounts are:
Total fat intake (in calories)
15% - Monounsaturated fat
10% - Polyunsaturated
<10% - Saturated fats

41. A. GOOD FATS VS. BAD FATS
Studies also indicate that:
Saturated fats are considered “bad fats”
Monounsaturated fats are considered “good fats”
Trans-monounsaturated fats are considered “bad fats”
Polyunsaturated fats can be both “good fats” and “bad fats”
 Omega 3 and 6 are important “good fats”

42. A. GOOD
FATS AND
BAD FATS
The figure shows the
percentages of
saturated,
monounsaturated, and
polyunsaturated fatty
acids in the
triacylglycerols of
various dietary fats
and oils.

43. B. Fat and Fatty Acid Composition of
Nuts
Numerous studies now indicate that eating nuts can have a strong protective effect against
coronary heart disease:
 Low amounts of saturated fatty acids
 Nuts also contain
valuable antioxidant vitamins, minerals,
and plant fiber protein that
is good for the brain.

44. C. ESSENTIAL FATTY ACIDS
ESSENTIAL FATTY ACID – is a fatty acid needed in the human body that must be obtained from
dietary sources because it cannot be synthesized within the body, in adequate amounts, from
other substances.
TWO MOST IMPORTANT ESSENTIAL FATTY ACIDS:
 Linoleic Acid (omega-6)
 Linolenic Acid (omega-3)
Deficiencies of the above two acids may result in skin redness, infections, and dehydration
and liver abnormalities may develop.
Both are needed for
1. proper membrane structure and;
2. serve as starting materials for the
production of several nutritionally important
longer-chain omega acids

45. C. ESSENTIAL FATTY ACIDS
If the fatty acids are restored, then the conditions reverse themselves. Infants are
especially in need of these acids for their growth. Human breast milk has a much higher
percentage of the essential fatty acids than cow’s milk.
1. Linoleic acid is the starting material for the biosynthesis of arachidonic acid
Arachidonic acid is the major starting material for eicosanoids, that help regulate
blood pressure, clotting, and several other important body functions.

46. C. ESSENTIAL FATTY ACIDS
2. Linolenic acid is the starting material for the biosynthesis of two additional omega-3
fatty acids.
EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are important
constituents of the communication membranes of the brain and are necessary for normal brain
development.
EPA and DHA are also active in the retina of the eye.

47. D. FATS SUBSTITUTES (ARTIFICIAL
FATS)
In response to consumer
demand for low-fat, low-calorie
foods, food scientists have
developed several types of
“artificial fats.” Such substances
replicate the taste, texture, and
cooking properties of fats but are
themselves not lipids.

48. D. FATS
SUBSTITUTES
(ARTIFICIAL
FATS)
Olestra looks, feels, and tastes
like dietary fat and can
substitute for fats and oils in
foods such as shortenings,
oils, margarines, snacks, ice
creams, and other desserts. It
has the same
Cooking properties such as
fats and oils.

49. CHEMICAL REACTIONS
OF TRIACYLGLYCEROLS

50. CHEMICAL REACTIONS
OF TRIACYLGLYCEROLS
A. HYDROLYSIS – it is the reverse of
the esterification reaction by which
triacylglycerol was formed.
TWO TYPES OF HYDROLYSIS
 Complete Hydrolysis – if all three
fatty acids were removed
 Partial Hydrolysis – if one or more
fatty acid residues remains attached
to the glycerol

51. CHEMICAL REACTIONS OF
TRIACYLGLYCEROLS
B. SAPONIFICATION – is a hydrolysis reaction carried out in an alkaline
(basic) solution. For fats and oils, the products of saponification are
glycerol and fatty acid salts.

52. THE CLEANSING ACTION
OF SOAP
The cleansing action
of soap is related to the
structure of the carboxylate
ions present in the fatty
acid salts of soap and the
fact that these ions readily
participate in micelle formation.
A micelle is a spherical cluster of molecules
in which the polar portions of the molecules are on
the surface, and the nonpolar portions are located in
the interior.

53. CHEMICAL
REACTIONS
OF
TRIACYLGLYCEROLS
C. HYDROGENATION
– Addition of
hydrogen across
double (=) bond to
increase degree of
saturation.

54. Many food products are produced by partial hydrogenation of
oils and fats.
 Peanut oil + 𝐻2 → Peanut Butter
 Vegetable oil + 𝐻2 → Margarine

55. TRANS FATTY ACIDS AND
BLOOD CHOLESTEROL
LEVELS
TRANS-FAT
The latter cis–trans conversions affect
the general shape of the fatty acid residues,
which in turn affects the biochemical behavior
of the triacylglycerols.
In the preceding diagram, note how
conversion of a cis,cis-18:2 fatty acid to a
trans,trans-18:2 fatty acid affects molecular
shape. The trans,trans-18:2 fatty acid has a
shape very much like that of an 18:0 saturated
fatty acid (the structure on the right).

56. TRANS FATTY
ACIDS AND
BLOOD
CHOLESTEROL
LEVELS
A label of “zero grams trans fat
per serving” on a product does
not mean the product is
absolutely trans-fat free. FDA
regulations allow trans fat
levels of less than 0.5 gram per
serving to be labeled as 0
grams per serving.
Studies show that
fatty acids with
trans double bonds
affect blood
cholesterol levels
in a manner similar
to saturated fatty
acids.

57. CHEMICAL REACTIONS OF
TRIACYLGLYCEROLS
D. OXIDATION
 double bonds in triacylglycerols are subject to oxidation with oxygen in air and
leads to C=C breakage and may result into two short chain molecules – an
aldehydes or a carboxylic acid:
 The aldehydes and/or carboxylic acids so produced often have objectionable
odors - fats and oils are said to be rancid
 To avoid this unwanted oxidation process antioxidants are added as
preservatives, e.g., Vitamin C and vitamin E are good antioxidant
preservatives.

58. MEMBRANE
LIPIDS:
PHOSPHOLIPIDS,
SPHINGOGLYCOLIPIDS, &
CHOLESTEROLS

59. MEMBRANE LIPIDS: PHOSPHOLIPIDS
All cells are surrounded by a membrane that confines their contents. Up
to 80% of the mass of a cell membrane can be lipid materials – dominated by
phospholipids.
A. PHOSPHOLIPIDS – contains one or more fatty acids, a phosphate group, a
platform molecule (glycerol or sphingosine) to which the fatty acid(s) and the
phosphate group are attached, and an alcohol that is attached to the
phosphate group.

60. MEMBRANE LIPIDS: PHOSPHOLIPIDS
TWO TYPES OF PHOSPHOLIPIDS

61. MEMBRANE LIPIDS: PHOSPHOLIPIDS
1. GLYCEROPHOSPHOLIPIDS
– is a lipid that contains two
fatty acids and a phosphate
group esterified to a glycerol
molecule and an alcohol
esterified to the phosphate
group.
All bonds between groups in a glycerophospholipid are ester linkages, similar to that in
triacylglycerols. However, glycerophospholipids have four ester linkages as contrasted to three ester linkages in
triacylglycerols.

62. MEMBRANE LIPIDS:
PHOSPHOLIPIDS
Structurally glycerophospholipids are
although similar to triacylglycerols, they have
different biochemical functions.
 Triacylglycerols serve as energy storage
molecules
 Glycerophospholipids function as components of
cell membranes
 Triacylglycerols are a non-polar
 Glycerophospholipids are polar.

63. MEMBRANE LIPIDS: PHOSPHOLIPIDS
Sphingophospholipids have structures based on the 18-carbon monounsaturated
aminodialcohol sphingosine.
2. SPHINGOPHOSPHOLIPIDS
– is a lipid that contains one
fatty acid and one phosphate
group attached to a
sphingosine molecule and an
alcohol attached to the
phosphate group.

64. MEMBRANE LIPIDS:
SPHINGOGLYCOLIPIDS
The second of the three major types of
membrane lipids is sphingoglycolipids.
B. SPHINGOGLYCOLIPIDS
– is a lipid that contains
both a fatty acid and a
carbohydrate component
attached to a sphingosine
molecule.

65. MEMBRANE LIPIDS:
SPHINGOGLYCOLIPIDS
EXAMPLES OF SPHINGOGLYCOLIPIDS:
1. CEREBROSIDE
 The simplest sphingoglycolipids
 It contain a single monosaccharide unit—either glucose
or galactose.
 As the name suggests, cerebrosides occur primarily in
the brain (7% of dry mass).
 They are also present in the myelin sheath of nerves.
 The specific structure for a cerebroside in which stearic
acid (18:0) is the fatty acid and galactose is the
monosaccharide

66. MEMBRANE LIPIDS:
SPHINGOGLYCOLIPIDS
EXAMPLES OF SPHINGOGLYCOLIPIDS:
2. GANGLIOSIDES
 A complex type of sphingoglycolipids
 It contained a branched chain of up to seven
monosaccharide residues.
 Occur in the gray matter of the brain as well as in the
myelin sheath.

67. MEMBRANE LIPIDS: CHOLESTEROLS
Cholesterol, the third of the three major types of membrane lipids, is a specific
compound rather than a family of compounds like the phospholipids and
sphingoglycolipids.
Cholesterol’s structure differs markedly from that of other membrane lipids in
that:
(1) there are no fatty acid residues present and
(2) neither glycerol nor sphingosine is present as the platform molecule.

68. MEMBRANE LIPIDS: CHOLESTEROLS
 Cholesterol is a steroid.
A steroid is a lipid whose
structure is based on a fused-ring
system that involves three 6-membered
rings and one 5-membered ring. This
steroid fused-ring system, which is
called the steroid nucleus, has the
following structure:

69. MEMBRANE LIPIDS:
CHOLESTEROLS
C. CHOLESTEROL
 It is a C27 steroid molecule that is a component of cell
membranes and a precursor for other steroid-based
lipids.
 It is the most abundant steroid in the human body.
 The principal constituent of gallstones from which it can
be isolated as white crystalline solid; name derived
from this source (Greek, chole – bile; steros – solid)
 Important in human cell membranes, nerve tissue and
brain tissue and in chemical synthesis of various
hormones and vitamins essential for life.

70. CHOLESTEROL IN FOODS
 Liver synthesizes cholesterol: ~ 1g everyday; so it is not necessary to consume in
the form of diet
 Ingested cholesterol decreases biosynthetic cholesterol production. However, the
reduction is less than the amount ingested. Therefore, total body cholesterol levels
increase with increased dietary intake of cholesterol.
 Plant foods contain negligible amounts of cholesterol; cholesterol is found primarily
in foods of animal origin.

71. CHOLESTEROL IN FOODS
 Medical science now considers
high blood cholesterol, along
with high blood pressure and
smoking, as the major risk
factors for cardiovascular
disease (CVD). High blood
cholesterol contributes to
atherosclerosis, which is
characterized by the buildup of
plaque along the inner walls of
the arteries.

72. CHOLESTER
OL IN
FOODS
The table shows the
amount of
cholesterol found
in various foods.

73. CELL MEMBRANE
CELL MEMBRANES
 is a lipid-based structure that separates a cell’s aqueous-based interior from the
aqueous environment surrounding the cell.
 It also controls the movement of substances into and out of the cell.
 The membranes are lipid bilayer made up of phospholipids.

74. CELL MEMBRANE
A lipid bilayer is a
two-layer-thick
structure of
phospholipids and
glycolipids in which the
nonpolar tails of the
lipids are in the middle
of the structure and the
polar heads are on the
outside surfaces of the
structure.

75. CHOLESTEROL & CELL
MEMBRANE
Cholesterol molecules are also
components of plasma membranes:
 Cholesterol helps regulate membrane fluidity
– The fused ring system does nor allow
rotation of fatty acid tails in the vicinity
 Fits between fatty acid chains of the lipid
bilayer: Make it rigid
 Cholesterol thus acts a membrane plasticizer

76. TRANSPORT PROCESSES ACROSS
CELL MEMBRANES
In order for cellular processes to be maintained, molecules of
various types must be able to cross cell membranes. Three common
transport mechanisms exist by which molecules can enter and leave cells.
They are:
1. Passive transport
2. Facilitated transport
3. Active transport.

77. TRANSPORT PROCESSES
ACROSS CELL MEMBRANES
1. PASSIVE TRANSPORT
 a substance moves across a cell membrane
by diffusion from a region of higher
concentration to a region of lower
concentration.
 Only a few types of molecules, including O2,
N2, H2O, urea, and ethanol, can cross
membranes by passive transport

78. TRANSPORT PROCESSES
ACROSS CELL MEMBRANES
2. FACILITATED TRANSPORT
 a substance moves across a cell membrane
with the aid of a membrane protein from a
region of higher concentration to a region of
lower concentration.
 The specific protein carriers or transporters
are involved in the process

79. TRANSPORT PROCESSES
ACROSS CELL MEMBRANES
3. ACTIVE TRANSPORT
 a substance moves across a cell membrane,
with the aid of membrane proteins, against a
concentration gradient with the expenditure
of cellular energy.
 Proteins involved in active transport are
called “pumps.” The needed energy is
supplied by molecules such as ATP

80. EMULSIFICATION LIPIDS:
BILE ACIDS

81. EMULSIFICATION LIPIDS: BILE ACIDS
An emulsifier is a substance that can disperse and stabilize water-insoluble
substances as colloidal particles in an aqueous solution.
BILE ACIDS
 It is a cholesterol derivative that functions as a lipid-emulsifying agent that facilitate
the absorption of dietary lipids in the intestine.
 Approximately one-third of the daily production of cholesterol by the liver is
converted to bile acids
 Its mode of action is much like that of soap during washing.

82. EMULSIFICATION LIPIDS: BILE ACIDS
https://www.osmosis.org/learn/Bile_secretion_and_enterohepatic_circulation
The medium through
which bile acids are supplied to
the small intestine is bile.
Bile is a fluid containing
emulsifying agents that are
secreted by the liver, stored in
the gallbladder, and released
into the small intestine during
digestion.

83. EMULSIFICATION LIPIDS: BILE ACIDS
Increased secretion of
cholesterol can upset the balance
between the cholesterol present in
bile and the bile acid derivatives
needed to maintain cholesterol’s
solubility in the bile. The result is
the precipitation of crystallized
cholesterol from the bile and the
resulting formation of gallstones in
the gallbladder.

84. MESSENGER LIPIDS:
STEROID HORMONES
& EICOSANOIDS

85. MESSENGER LIPIDS
An additional role played by lipids is that of “chemical messenger.”
HORMONES
 is a biochemical substance, produced by a ductless gland, that has a messenger
function.
 serve as a means of communication between various tissues
 Some hormones, though not all, are lipids.

86. MESSENGER LIPIDS: STEROID
HORMONES
Steroid hormones and eicosanoids are two large families of lipids that have
messenger functions.
1. STEROID HORMONES – derivatives of cholesterol.
There are two classes of steroid hormones:
A. Sex Hormones – control reproduction and secondary sex characteristics
B. Adrenocorticoid Hormones – controls numerous biochemical process in the body

87. MESSENGER LIPIDS:
STEROID HORMONES
A. SEX HORMONES – Sex hormones can be
classified into three major groups.
 Estrogens—the female sex hormones
 Androgens—the male sex hormones
 Progestins—the pregnancy hormones
Structures of selected sex hormones and synthetic
compounds that have similar actions.

88. MESSENGER LIPIDS:
STEROID HORMONES
B. ADRENOCORTICOID HORMONES –
Produced by the adrenal glands, small
organs located on top of each kidney. There
are two types of adrenocorticoid hormones:
 Mineralocorticoids – control the balance of
Na and K ions in cells and body fluids.
 Glucocorticoids – control glucose
metabolism and counteract inflammation.
Structures of selected adrenocorticoid hormones and
related synthetic compounds.

89. MESSENGER LIPIDS: EICOSANOIDS
The term eicosanoid is derived from the Greek word eikos, which means
“twenty.”
2. EICOSANOIDS – derivatives of arachidonic acid.
 Have profound physiological effects at extremely low concentrations.
 Eicosanoids are hormone-like molecules
 Exert their effects in the tissues where they are synthesized.
 Eicosanoids usually have a very short “life.”

90. MESSENGER LIPIDS: EICOSANOIDS
Physiological effects of eicosanoids:
 Inflammatory response
 Production of pain and fever
 Regulation of blood pressure
 Induction of blood clotting
 Control of reproductive functions, such as induction of labor
 Regulation of the sleep/wake cycle

91. MESSENGER LIPIDS:
EICOSANOIDS
There are three principal types of
eicosanoids:
A. Prostaglandins
B. Thromboxanes
C. Leukotrienes.

92. MESSENGER LIPIDS: EICOSANOIDS
A. PROSTAGLANDINS – named after the prostate gland, which was first
thought to be their only source
Prostaglandins are involved in many regulatory functions:
 Involved in raising body temperature,
 Inhibiting the secretion of gastric juices,
 Increasing the secretion of a protective mucus layer into the stomach,
 Relaxing and contracting smooth muscle, directing water and electrolyte
balance, intensifying pain, and enhancing inflammation responses.

93. MESSENGER LIPIDS: EICOSANOIDS
B. THROMBOXANES – produced by blood platelets
Thromboxanes is involved in:
 promoting the formation of blood clots,
 promote platelet aggregation
C. LEUKOTRIENES – are found in leukocytes (white
blood cells)
Leukotrienes is involved in:
 Promoting inflammatory and hypersensitivity (allergy)
responses

94. PROTECTIVE-COATING
LIPIDS:
BIOLOGICAL WAXES

95. PROTECTIVE-COATING LIPIDS:
BIOLOGICAL WAXES
BIOLOGICAL WAX
 It is a lipid that is a monoester of a long-chain fatty acid and a long-chain alcohol.
 Biological waxes are monoesters, unlike fats and oils, which are triesters.
 The fatty acids found in biological waxes generally are saturated
 The fatty acids contain 14 to 36 carbon atoms.
 The alcohols found in biological waxes may be saturated or unsaturated and may contain
from 16 to 30 carbon atoms.

96. PROTECTIVE-COATING LIPIDS:
BIOLOGICAL WAXES
A biological wax has a structure with a small, weakly polar
“head” and two long, nonpolar “tails.” The polarity of the small
“head” is not sufficient to impart any degree of water solubility to
the molecule.
Plant leaves
often have a
biological wax
coating to
prevent
excessive loss
of water.

97. TRANSPORT LIPIDS:
LIPOPROTEINS

98. TRANSPORT LIPIDS:
LIPOPROTEINS
Four major classes:
1. Chylomicrons – transport dietary TAG (Tr from the
intestine to the liver and to adipose tissue
2. Very-low-density lipoprotein (VLDL) – transport
TAG synthesized in the liver to adipose tissue
3. Low-density lipoprotein (LDL) – transport
cholesterol synthesized in the liver to cells throughout
the body
4. High-density lipoprotein (HDL) – collect excess
cholesterol from body tissues and transport it back to
the liver for degradation to bile acids

99. References:
Books
 General, Organic, and
Biological Chemistry by
H. STEPHEN STOKER