BIOCHEMISTRY LIPIDS - Even # of Carbon atoms:

● Long chain fatty acids:

Lipids C12 - C26
- Organic compound found in living ● Medium chain fatty acids:
organism C8 – C10
- Insoluble in water but soluble in ● Short-chain fatty acids:
non-polar organic solvents [alcohol] C4 – C6
- They do not have a common
structural features that serves as the Types of Fatty Acids
basis for defining such compounds 1. Saturated Fatty Acids
- Classification: [classified on the - All C-C bonds are single
basis of solubility not my functional bonds
groups] - Numbering starts from the
● Insoluble or sparingly soluble end of -COOH group
in water - See structural notation: it
● Soluble in non-polar organic indicates number of C atoms
solvents [alcohol] - Example: Lauric acid has 12
C atoms and no double
Five Categories of Lipids: bonds so it is (12:0)
1. Energy-storage Lipids
- Triacylglycerols 2. Unsaturated Fatty Acids
2. Membrane Lipids ● MUFAs [Monounsaturated
- Phospholipids, Fatty Acid]
sphingoglycolipids, and - Is a fatty acid with a
cholesterol carbon chain in which
3. Emulsification lipids one C-C double bond
- Bile Acids is present
4. Chemical Messenger Lipids - Different ways of
- Steroid hormones and depicting the
eicosanoids structure
5. Protective-coating Lipids
- Biological waxes

Structural Formulas
- Lipids exhibit structural diversity
- Some are esters, some are amides,
and some are alcohols [acyclic and
cyclic] and some are polycyclic.

Fatty Acids
- Carboxylic acids with linear
(unbranched) carbon chain
- Naturally occuring monocarboxylic
acids
● PUFAs [Polyunsaturated Selected Fatty Acids of Biological
Fatty Acid] Importance
- A fatty acid with a
carbon chain in which
two or more C-C
double bonds are
present
- Up to six double
bonds are found in
biochemically
important PUFAs

- Two Types of Unsaturated

Fatty Acids:
● Omega (ω)-3 fatty
acids
- Its endmost
double bond
three carbon
atoms away
from its methyl
end.
- Abundant in
Fish [fish oils]

● -Omega (ω)-6 fatty

acids
- Its endmost
double bond six
carbon atoms > Selected Unsaturated Fatty Acids of
away from its Biological Importance
methyl end - Numbering starts from other end of
COOH
- Structural Notation: Indicates
number of Atoms
● E.g. [18:2] = 18 carbons, 2
double bonds
> Omega Acids Physical Properties of Fatty Acids
- Essential Fatty Acids: Must be part 1. Water solubility:
of diet ● Short chain fatty acids have
- Nutritional Important Omega-3 and 6 some solubility whereas long
fatty acids chain fatty acids are
● Linolenic Acid = Omega-3 insoluble
● Linoleic Acid = Omega-6 ● Short chain fatty acids are
- Lenoleic Acid Deficiency: sparingly soluble because of
● Skin redness -> irritated carboxylic acid polar group
● Infections and dehydration - Physical properties such as melting
● Liver abnormalities point depends on the number of C
● Children need it most atoms and degree unsaturation
● Contains more in human milk
than cow’s milk 2. The Melting Point
- Melting Point Depends Upon:
> American Diet ● Length of carbon chain
- Sufficient in omega 6 fatty acids ● Degree of unsaturation
- Deficient in omega 3 fatty acids [number of double bonds in a
● Fish = good source for molecule]
omega 3 fatty acids
- High rate of heart disease may be 3. Space-Filling Molecules
due to imbalance in omega 3 and 6 - The number of bends in a fatty acid
fatty acids chain increase as the number of
● Ideal ratio: Omega 6 : double bonds increase
Omega 3 (4 - 10 g: 1g) ● Less packing occurs
● Melting point is lower
● Tend to be liquids at room
temperature
Energy-Storage Lipids: Triacylglycerols different
- Energy-Storage Materials triacylglycerols
● With the notable exception of
nerve cells, human cells
store small amounts of
energy providing materials:
- The most widespread
energy storage
material:carbohydrate
glycogen
- Present in small
amounts
● Storage material is the
triacylglycerols:
- Triacylglycerols are
concentrated
primarily in special
cells (adipocytes)
- Nearly filled with the
material

- Two Types of Triacylglycerols

● Simple Triacylglycerols
- Three identical fatty
acids are esterified
- Natural occurring
simple triacylglycerols
are RARE
- Difference of Fats and Oils
● Physical State:
● Mixed Triacylglycerol
- Fats
- A triester formed
● Predominantly
from the esterification
Saturated
of glycerol with more
● Solids or semisolids
than one kind of fatty
at room temperature
acid
● Source: Animal
- In nature mostly
source and tasteless
mixed triacylglycerols
- Oils
are found and are
● Predominantly
different even from
unsaturated
the same source
● Liquid at room
depending on the
temperature
feed
● Source: Plants and
- e.g., corn, peanut and
fish oil
wheat -fed cows have
* Pure oils and fats are colorless, odorless
 ● <10% - Saturated
fats
- Studies also indicate
that:
● Saturated fats are
considered “bad fats”
● Monounsaturated
fats are considered
“good fats”
● Trans-monounsatura
ted fats are
considered “bad fats”
● Polyunsaturated fats
Dietary Considerations and Triacylglycerols can be both “good
- Studies fats” and “bad fats”
● Nations whose citizens have *Omega 3 and 6 are
high dietary intakes of fats important “good fats”
and oils tend to have higher
incidences of heart disease - Essential Fatty Acids
and certain types of cancers ● Fatty acids that must be
● Typical American diet obtained from dietary
contains too much fat and sources – are not
therefore the Americans are synthesized within the body
being asked to reduce their
total dietary fat intake ● Two most important
● Other studies show that risk essential fatty acids are:
factor is more than simply the - Linoleic acid (18:2) =
total amount of omega 6
triacylglycerols consumed - Linolenic acid (18:3) =
omega 3
- “Good Fats” Versus “Bad Fats” ● Both are needed
● Studies indicate that type of for:
dietary fat and amount of - Proper membrane
dietary fat are important for structure
balanced diet: - Serve as starting
- Current materials for the
recommended production of
amounts are: total fat several nutritionally
intake in calories: important
● 15% - longer-chain
Monounsaturated fat omega-6 and
● 10% - omega-3 fatty
Polyunsaturated acids
 ● Deficiencies of above two Chemical Reactions of Triacylglycerols
acids may result in skin - Partial Hydrolysis
redness, infections and ● Chemical Properties due to
dehydration likely and liver two functional groups: esters
abnormalities may develop and alkenes
- Hydrolysis: Partial
hydrolysis of
triacylglycerols
- Breaking of 1-2 ester
bonds to give rise to
mono- or
diacylglycerol and
fatty acid(s)
- Carried out by
enzymes produced by
Fat and Fatty Acid Composition of Nuts the pancreas
- Numerous studies now indicate that - Saponification
eating nuts can have a strong ● Hydrolysis in basic solution:
protective effect against coronary Produce salt of fatty acid and
heart disease: glycerol
● Low amounts of saturated RCOOR’ +
fatty acids NaOH
● Nuts also contain valuable RCOONa
antioxidant vitamins, (soap) + R’OH
minerals, and plant fiber
protein
- Hydrogenation Membrane Lipids: Phospholipids
● Addition of hydrogen across - All cells are surrounded by a
double (=) bond - increases membrane that confines their
degree of saturation contents.
- Up to 80% of the mass of a cell
membrane can be lipid materials
and these lipid materials are
dominated by phospholipids.
- A phospholipid contains one or more
fatty acids, a phosphate group, a
platform molecule (glycerol or
● Many food products are sphingosine) to which the fatty
produced by partial acid(s) and the phosphate group are
hydrogenation of oils and fats attached, and an alcohol that is
● Peanut oil + H2 -> Peanut attached to the phosphate group.
Butter
● Vegetable oil + H2 ->
Margarine

- Oxidation
● Double bonds in
triacylglycerols are subject to
oxidation with oxygen in air
(an oxidizing agent )-Leads
to C=C breakage
● Remember that oxidation of
alkenes may result into two
short chain molecules – an
aldehydes or a carboxylic
acid: ● Glycerophospholipids
- The aldehydes and/or - A glycerophospholipid is a
carboxylic acids so lipid that contains two fatty
produced often have acids and a phosphate group
objectionable odors - esterified to a glycerol
fats and oils are said to molecule and an alcohol
be rancid esterified to the phosphate
- To avoid this unwanted group.
oxidation process - All attachments (bonds)
antioxidants are added between groups in a
as preservatives, glycerophospholipid are ester
- e.g., Vitamin C and linkages
vitamin E are good - Glycerophospholipids have
antioxidant four ester linkages as
preservatives.
 contrasted to three ester - Contains one fatty acid and
linkages in triacylglycerols. one phosphate group
- Glycerophospholipids attached to a sphingosine
undergo hydrolysis and molecule and an alcohol
saponification reactions in a attached to the phosphate
manner similar to that for group
triacylglycerols - Saponifiable lipids
- The alcohol attached to the - Which the alcohol esterified
phosphate group in a to the phosphate group is
glycophospholipid is usually choline are called
one of three amino alcohols: sphingomyelins.
choline, ethanolamine, or - Sphingomyelins are found in
serine - respectively known all cell membranes and are
as phosphatidylcholines, important structural
phosphatidylethanolamines, components of the myelin
and phosphatidylserines. sheath of neurons
- Structurally - Contains both a fatty acid
glycerophospholipids are and carbohydrate
although similar to - Cerebrosides:
triacylglycerols, they have ● Simple
different biochemical sphingoglycolipids
functions. ● Contains a single
● Triacylglycerols serve monosaccharide unit -
as energy storage either glucose or
molecules galactose
● Glycerophospholipids ● They occur primarily in
function as brain (7% of dry mass)
components of cell
membranes
- A major structural difference
between the two types of
lipids is that of their “polarity”
– Responsible for the their
differing biochemical
functions.
● Triacylglycerols are a - Gangliosides
non-polar ● Complex
● Glycerophospholipids Sphingoglycolipids
are polar. ● Contain a branched chain
of up to seven
● Sphingophospholipids monosaccharide residues
- Structures based on the ● Occur in the gray matter
18-carbon monounsaturated of the brain as well as in
aminodialcohol sphingosine the myelin sheath
Membrane Lipids: Cholesterol Cell Membranes
- Third major type of membrane lipid ● Cells are surrounded by plasma
- Lipids: C27 steroid Molecule membranes:
- Steroid - Separates aqueous interior
● A lipid whose structure is of a cell from the aqueous
based on a fused ring system environment surrounding the
of three 6 carbon rings and cell
one 5 carbon ring - Up to 80% of plasma
● Important in human cell membrane is lipid material
membranes, nerve tissue - The membranes are lipid
and brain tissue bilayer made up of
● Important in chemical phospholipids
sythesis: Hormones, vitamins ● Cells are surrounded by plasma
essential for life membranes:
- Bilayer: Nonpolar tails of
- Cholesterol in Food phospholipids in the middle
● Liver synthesizes cholesterol: and polar heads are on the
~ 1g everyday; so it is not surface
necessary to consume in the ● 6 - 9 billionths of a
form of diet meter thick or 6-9
● Cholesterol synthesis nanometer thick
decrease if it is ingested but - The membrane is a liquid like
reduction is not sufficient structure due to unsaturation
- Leads to in lipid tails
cardiovascular
disease
● Animal Food: Contains a lot
of Cholesterol
● Plant Food: No cholesterol

- Cholesterol
● Components of plasma
memnbranes
● Helps regulate mebrane fluidity
● The gused ring system does not
allow rotation of fatty acid tails in
the vicinity
● Fits between fatty acid chain of
the lipid bilayer: Make it rigid
● Acts as a membrane plasticizer
Cell Membranes - Types of Transport:
- Proteins [Membranes] 1. Passive Transport
● Responsible for moing - A substance moves
substances such as nutrients across a cell membrane
and elecctrolytes across the by diffusion from a region
membrane of higher concentration to
● Receptors for hormones and a region of lower
neurotransmitters concentration
● The membrane proteins and - Only a few typed of
some lipids are furuther molecules, including O2,
reacted with carbohydrates N2, H2O, urea, and
molecules ethanol, can cross
● Act as markers: process by membranes by passive
which different cells transport
recognize each other
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

3. Active Transport
- Transport Across Cell Membranes - A substance moves
● To maintain cellular across a cell membrane,
processes various molecules with the aid of membrane
transported across the cell proteins, against a
membranes concentration gradient
with the expenditure of
cellular energy
- Proteins involved in active
transport are called
“pumps”
- The needed energy is
supplied by molecules
succh as ATP
Emulsification Lipids: Bile Acids
- Emulsifier
● A substance that can
disperse and stabilize
water-insoluble substances
as colloidal particles in an
aqueous solution

- Bile Acids
● Cholesterol derivatives that
functions as emulsifying
agents that make dietary
lipids soluble in aqueous
environment of the digestive
tract: Messenger Lipids: Steroid Hormones
- Approximately one - Hormones
third of cholesterol ● A biochemical substance
produced by liver is produced bu a ductless gland
converted to bile that has a messenger
acids function
- Action similar to soap ● Serve as a means of
in washing communication between
● Are tri- or dihydroxy various tissues
cholesterol derivatives ● Some hormones are lipids
● The carbon 17 side chain of - The lipids that play the role off
cholesterol has been “chemical messengers” include:
oxidized to a carboxylic acid ● Steriod hormones -
● The oxidized acid side chain derivatives of cholesterol
is bonded to an amino acid ● Eicosanoids - derivatives of
(either glycine or taurine) arachidonic acid
through an amide linkage
● Bile is a fluid containing - Two Major Classes of Steroid
emulsifying agents (Bile Hormones:
acids) secreted by the liver, ● Sex hormones
stored in the gallbladder, and - Control reproductiosn
released into the small and secondary sex
intestine during digestion characteristics
● Lipid – emulsifying agent in ● Adrenocorticoid hormones
the aqueous environment of - Control numerous
the digestive tract biochemical
processes in the body
- Sex Hormones ● Two types of
● Three Major Groups: adrenocorticoid hormones:
- Estrogens - the female - Mineralocorticoids -
sex hormones; regulates control the balance of
menstrual cycle Na+ and K+ ions in
- Androgens - the male sex cells
hormones - Glucocorticoids -
- Progestin - the pregnancy control glucose
hormones; prevents metabolism and
ovulation counteract
inflammation
● Oral contraceptives
- Used to supress
ovulation as a method
of birth control

● Anabolic steroids
- Illegal steroid drugs
used bu some
athletes to build up
muscles strength and
enhance endurance

Messenger Lipids: Eicosanoids

● Eicosanoids Arachidonic acid
(20:4) derivatives:
- Have profound physiological
effects at extremely low
concentrations.
- Adrenocorticoid Hormones - Eicosanoids are
● Produced by the adrenal hormone-like molecules
glands [small organs located - Exert their effects in the
on top of each kidney] tissues where they are
● 28 Different hormones have synthesized.
been isolated from the - Eicosanoids usually have a
adrenal cortex very short “life.”
● Physiological effects of 2. Thromboxanes:
eicosanoids: C20-fatty-acid derivative
- Inflammatory response containing a cyclic ether ring
- Production of pain and fever and oxygen-containing
- Regulation of blood pressure functional groups
- Induction of blood clotting - Promote platelet
- Control of reproductive aggregation
functions, such as induction - Promote formation of
of labor blood clots
- Regulation of the sleep/wake
cycle 3. Leukotrienes:
C20-fatty-acid derivative
containing three conjugated
double bonds and hydroxy
groups
- Promote inflammatory
and hypersensitivity
(allergy) responses
- Found in WBC

Protective-Coating Lipids: Biological

Waxes
● A monoester of long-chain fatty acid
- Three Principal Types of and a long-chain alcohol
Eicosanoids ● The fatty acids found in biological
1. Prostoglandins: waxes
C20-fatty-acid derivative - Generally are saturated fatty
containing cyclopentane ring accids
and oxygen-containing - Contain 14 - 36 carbon
functional groups, named atoms
after the prostate gland ● The alcohols found in biological
- Involved in raising body waxes
temperature, - May be saturated or
- Inhibiting the secretion of unsaturated
gastric juices, - May contain 16 - 30 carbon
- Increasing the secretion atoms
of a protective mucus
layer into the stomach,
- Relaxing and contracting
smooth muscle, directing
water and electrolyte
balance, intensifying
pain, and enhancing
inflammation responses.
● Properties of Biological Waxes
- Water-insoluble and
water-repellent because of
long nonpolar hydrocarbon
chains
- Humans and animals secrete
biologiccal waxes from skin
galnds

● Function of biological waxes

- Protect hair and skin; and
keep it pliable and lubricated.
- Impart water repellency to
animal fur.
- Birds keep their feathers
water repellent and help
minimize loss of body heat
- Plants coat their leaves with
a thin layer of biological
waxes to prevent excessive
evaporation of water and to
protect against parasite
attack