LIPIDS Flashcards
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four major classes of bioorganic substances:
*carbohydrates,
*lipids,
*proteins
*nucleic acids.
known as ‘fats provide a major way of storing chemical energy and carbon atoms in the body.’
Lipids
(a lipid) are the basic components of cell
membranes.
Phospholipids, glycolipids,
and cholesterol
total daily caloric intake of lipid
25-45%
LIPIDS
saturated fatty acid
vitamins
sterols
polyunsaturated fatty acids
trans fatty acid
monounsaturated fatty acids
Lipid is an organic compound found in living organisms that is insoluble (or only sparingly soluble)
in water but soluble in nonpolar organic solvents.
STRUCTURE AND CLASSICATION OF LIPID
divide lipids into five
categories on the basis of lipid function:
- Energy-storage lipids (triacylglycerols)
- Membrane lipids (phospholipids, sphingoglycolipids,
and cholesterol) - Emulsification lipids (bile acids)
- Messenger lipids (steroid hormones and eicosanoids)
- Protective-coating lipids (biological waxes)
is a naturally occurring monocarboxylic
acid.
fatty acid
characterization of fatty acid (carbon chain length)
long-chain fatty acids (C12 to C26),
medium chain fatty acids (C8 and C10), or short-chain
fatty acids (C4 and C6).
classification of fatty acids
- saturated fatty acids (SFAs)
- monounsaturated fatty
acids (MUFAs) - polyunsaturated fatty acids (PUFAs).
fatty acid with a carbon chain in
which all carbon–carbon bonds are single bonds.
saturated fatty
a fatty acid with a carbon
chain in which one carbon–carbon double bond is
present.
monounsaturated fatty acid
MUFAs configuration
double bond is nearly always cis.
is a fatty acid with a carbon
chain in which two or more carbon–carbon double bonds
are present.
polyunsaturated fatty acid
Fatty acid family
Omega-3
Omega-6
Omega-9
Name and structure of Omega-3
Alpha-Linoleic acid (ALA) 18:3 (n-3)
Eicosapentanoic acid (EPA) 20:5 (n-3)
Docosahexaenoic acid (DHA) 22:6
(n-3)
Name an structure of Omega-6
Linoleic acid (LA) 18:2 (n-6)
Gamma-linoleic acid (GLA) 18:3 (n-6)
Arachidonic acid (ARA) 20:4 (n-6)
Name and structure of Omega-9
Oleic acid (OA) 18:1 (n-9)
an unsaturated fatty acid with
its endmost double bond three carbon atoms away from
its methyl end.
omega-3 fatty acid
an unsaturated fatty acid with
its endmost double bond six carbon atoms away from
its methyl end.
omega-6 fatty acid
physical properties of fatty acids
are largely determined by the length and degree of unsaturation of the fatty acid carbon chain.
solubility decreases as carbon
chain length increases.
▪Water solubility
slight solubility in water.
short-chain fatty acids
essentially insoluble in water.
Long-chain fatty acids
is related to the polarity of the carboxyl group present.
slight solubility of short-
chain fatty acids
the non-polar nature of the hydrocarbon chain completely dominates solubility considerations.
longer chain fatty acids
are strongly influenced by
both carbon chain length and degree of unsaturation
(number of double bonds present).
melting points
physical properties of fatty acids
As carbon chain
length increases, melting point increases.
energy storage in lipids
triacyclglycerols
also function
within the body as energy-storage materials.
triacyclglycerols (lipids)
triacylglycerols are
concentrated primarily in
special cells (adipocytes)
Adipose tissue
containing these cells is found in various parts of the
body:
under the skin, in the abdominal cavity, in the
mammary glands, and around various organs.
Triacylglycerols are much more efficient at storing
energy than
glycogen (because large quantities of them can be packed into a very small volume.)
large quantities of
them can be packed into a very small volume.
large quantities of
them can be packed into a very small volume.
a single molecule of glycerol reacts
with three fatty acid molecules;
esterification reaction
producing a triacylglycerol
is a lipid
formed by esterification of three fatty acids to a glycerol
molecule.
triacylglycerol/ triglyceride
is the portion of a carboxylic acid that remains after the —OH group is removed from the carboxyl
carbon atom.
An acyl group,
- is a triacylglycerol mixture that is a solid or a semi-solid at room
temperature (25 ̊C). - are obtained from animal sources.
- composed largely of triacylglycerols in which
saturated fatty acids predominate
fat
- triacylglycerol mixture that is a liquid at room temperature
(25 ̊C). - are obtained from plant sources.
- contain
triacylglycerols with larger amounts of mono- and
polyunsaturated fatty acids
oil
pack closely together thus causing the higher melting points associated with fats.
“linearity”
cannot pack as tightly together results is lower melting points.
“bends”
A fish would have
some serious problems if its triacylglycerols __________ when it encountered cold water.
“solidified”
are colorless, odorless, and
tasteless.
▪Pure fats and pure oils
Current dietary fat
recommendations are that people limit their total fat
intake to 30% of total calories—with up to
- 15% coming
from monounsaturated fat, - 10% from
- polyunsaturated fat,
- less than 10% from saturated
fats.
“bad fat”
saturated fats
“good fat”
monounsaturated fats
can be both “good fat” and “bad fat.”
polyunsaturated fats
fat that can increase heart disease risk
saturated fat
fat that can decrease both heart disease and breast cancer risk,
monounsaturated fat
can reduce heart disease risk but promote the risk of
certain types of cancers
polyunsaturated fat
Inuit people take exhibiting a low incidence of heart disease
omega -3 acids
U.S. population, which show a correlation
between a high-fat diet and a high incidence of heart
disease.
omega-6 fatty acids
are essential fats; have important benefit for your heart, brain and metabolism
omega-3
Controls blood clotting; enhances brain and joint function; muscle-building; reduces risk of
cancer, heart disease,
diabetes, inflammation
Fatty fish (salmon, mackerel, cod,
etc.)
Omega-3
Regulates brain functioning;
regulate growth and development;
stimulates hair and skin growth;
regulate metabolism; maintains
healthy bones and reproductive
system; increases inflammation
Most vegetable oils, nuts, and
grain-fed meats
Omega-6
Reduces inflammation; reduces
insulin resistance,
Produced naturally by the body,
Omega-7
Reduces inflammation; improves
joint health and healing; prevents
variety of diseases
can also be found in olive oil
and vegetable oils
Omega-9
mackerel omega-3s grams
2.3
needed in the human body that must be obtained from dietary sources
essential fatty acid
two essential fatty acids:
- Linoleic acid (18:2) - omega-6 acid family
- linolenic acid (18:3) - omega-3 acid family.
why essential fatty acids are important?
- needed for proper membrane structure
- starting materials for the production of several nutritionally important longer- chain omega-6 and omega-3 acids.
what happens when these 2 are missing (essential acids) from diet
skin reddens and becomes irritated,
infections and dehydration are likely to occur, and the liver may develop abnormalities.
has a much higher percentage of the essential fatty acids than cow’s milk.
Human breast milk
is the starting material for the biosynthesis of
arachidonic acid.
▪Linoleic acid
is the major starting material for
eicosanoids. Helps regulate blood pressure, clotting, and several other important body functions.
▪Arachidonic acid
is the starting material for the biosynthesis
of two additional omega-3 fatty acids.
Linolenic acid
are important constituents of the
communication membranes of the
brain and are necessary for normal
brain development.
are also active in the
retina of the eye.
▪EPA (eicosapentaenoic acid) and
DHA (docosahexaenoic acid)
CHEMICAL REACTIONS OF TRIACYLGLYCEROLS
▪Hydrolysis
▪Saponification
▪Hydrogenation
▪Oxidation
is the reverse of the esterification
reaction by which it was formed.
Hydrolysis of a triacylglycerol
Triacylglycerol hydrolysis setting, requires the presence of an
acid or a base.
hydrolysis products are
glycerol and fatty acids.
acidic conditions,
is a reaction carried out in an
alkaline (basic) solution.
▪Saponification
the hydrolysis
products are glycerol and fatty acid salts
basic conditions,
FIGURE OF 1ST STEP
first step is the hydrolysis of the ester linkages to produce glycerol and three fatty acid molecules:
fat or oil + 3H2O → 3 fatty acids + glycerol
For fats and oils, the
products of saponification are
glycerol and fatty
acid salts.
FIGURE OF 2ND STEP
second step involves a reaction between the fatty
acid molecules and the base (usually NaOH) in the
alkaline solution. This is an acid–base reaction that
produces water plus salts:
3 fatty acids + 3NaOH → 3 fatty acid salts + 3H2O
__ of animal fat is the process by which soap was made in pioneer times.
▪Saponification
Soap making involved heating
lard (fat) with lye (ashes of wood, an impure form of KOH).
soap is prepared by
hydrolyzing fats and oils under high pressure and high temperature.
base of the soap
sodium carbonate
is a chemical reaction involves hydrogen addition across carbon–carbon multiple bonds, which increases the degree of saturation as some double bonds are converted to single bonds.
Hydrogenation
carbon–carbon double bonds present in the fatty acid
residues of a triacylglycerol
oxidation with
molecular oxygen (from air) as the oxidizing agent.
Two naturally occurring antioxidants
vitamin C and vitamin E.
% mass of a cell membrane can
be lipid materials; the rest is primarily protein.
80%
three common
types of membrane lipids:
phospholipids,
sphingoglycolipids, and cholesterol.
most abundant type of
membrane lipid.
▪Phospholipids
platform molecule on which a
phospholipid is built
the 3-carbon alcohol glycerol
or a more complex C18 aminodialcohol called sphingosine.
Glycerol-based phospholipids
glycerophospholipids,
based on sphingosine
sphingophospholipids
lipid that contains two fatty acids and a phosphate group esterified to a glycerol molecule and an
alcohol esterified to the phosphate group.
glycerophospholipid
glycerophospholipids have four ester linkages as contrasted to three
ester linkages in
triacylglycerols.
have structures based on the 18-carbon
monounsaturated aminodialcohol sphingosine.
Sphingophospholipids
is a lipid that contains
both a fatty acid and a carbohydrate component attached to a
sphingosine molecule.
sphingoglycolipid
the third of the three major types of membrane lipids,
- is a steroid
▪Cholesterol,
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.
is a lipid whose structure is based on a fused- ring system that involves three 6-membered rings and one 5-membered ring.
steroid
is a C27 steroid molecule that is a
component of cell membranes and a precursor for
other steroid-based lipids.
▪Cholesterol
-ol ending in the name cholesterol
conveys the information that an ____ functional group is present; located on carbon 3 of the steroid nucleus.
alcohol functional group
high food cholesterol with 410 mg
liver
is a lipid-based structure
that separates a cell’s aqueous-based interior from the
aqueous environment surrounding the cell.
cell membrane
is a two-layer-thick structure of
phospholipids and glycolipids with polar heads and non polar tails
lipid bilayer
three distinct parts to the bilayer:
- exterior polar “heads,”
- the interior polar “heads,”
- central nonpolar “tails,”
the transport process in which a substance moves across a cell membrane by diffusion from a region of higher concentration to a region of lower concentration without the cellular energy.
Passive transport
few types of molecules that can cross membranes in this manner.
O2, N2, H2O, urea, and ethanol,
transport process in which a substance moves across a cell membrane, with the aid of membrane proteins,
from a region of higher concentration to a region of lower
concentration without the expenditure of cellular energy.
Facilitated transport
transport process in which a substance moves across a cell membrane, with the aid of membrane proteins, against a
concentration gradient with the expenditure of cellular energy.
Active transport
is a substance that can disperse and stabilize water-insoluble substances as colloidal particles in an aqueous solution.
emulsifier
Cholesterol derivatives called __ function as emulsifying agents that facilitate the absorption of dietary lipids in the intestine.
bile acids
bile acids differ structurally from
cholesterol in three respects:
- They are **tri- or dihydroxy ** cholesterol derivatives.
- The carbon 17 side chain of cholesterol has been oxidized to a
carboxylic acid. - The oxidized acid side chain is bonded to an amino acid
(either glycine or taurine)through an amide linkage.
is a biochemical substance, produced by a
ductless gland, that has a messenger function.
hormone
is a hormone that is a cholesterol
derivative.
steroid hormone
There are two major classes of steroid hormones:
(1) sex hormones (control
reproduction and secondary sex characteristics)
(2) adrenocorticoid hormones (regulate numerous biochemical processes in the body.)
▪The sex hormones can be classified into three major
groups:
- Estrogens—the female sex hormones
- Androgens—the male sex hormones
- Progestins—the pregnancy hormones
are synthesized in the ovaries and adrenal cortex and are
responsible for the development of female secondary sex
characteristics at the onset of puberty and for regulation of the
menstrual cycle.
Estrogens
are synthesized in the testes and adrenal cortex and promote the development of secondary male characteristics.
- promote muscle growth
Androgens
are synthesized in the ovaries and the placenta and prepare the lining of the uterus for implantation of the fertilized ovum.
- They also suppress ovulation
Progestins
second major group of steroid hormones consists of the
adrenocorticoid hormones.
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.
is an oxygenated C20 fatty acid derivative that functions as a messenger lipid.
eicosanoid
eicosanoid is derived from the Greek word eikos, which means
“twenty.”
The metabolic precursor for most eicosanoids is
arachidonic acid, the 20:4 fatty
acid.
The physiological effects of eicosanoids include mediation of
- The inflammatory response, a normal response to tissue damage
- The production of pain and fever
- The regulation of blood pressure
- The induction of blood clotting
- The control of reproductive functions, such as induction of labor
- The regulation of the sleep/wake cycle
is a messenger lipid that is a C20-
fatty-acid derivative that contains a cyclopentane ring and oxygen-containing functional groups.
prostaglandin
prostaglandins regulatory functions
raising body
temperature, inhibiting the secretion of gastric juices, relaxing and contracting smooth
muscle, directing water and electrolyte balance, etc.
reduces inflammation and fever because it inactivates the enzyme needed for prostaglandin synthesis.
Aspirin
is a messenger lipid that is a C20-fatty-acid derivative that contains a cyclic ether ring and oxygen-containing functional
groups.
thromboxane
important function of thromboxanes
formation of blood clots.
Thromboxanes are produced by
blood platelets and promote platelet aggregation.
is a messenger lipid that is a
C20-fatty-acid derivative that contains three conjugated double bonds and hydroxy groups.
leukotriene
Leukotrienes are found in
leukocytes (white blood cells).
is a lipid that is a monoester of a long-chain fatty acid and a
long-chain alcohol.
biological wax
Biological waxes are ______ unlike fats and oils, which
are _________
monoesters, triesters.
is a pliable, water-repelling substance used particularly in
protecting surfaces and producing polished surfaces.
▪Wax
is a particularly hard wax whose uses involve high-
gloss finishes:
Carnauba wax (Brazilian palm tree)
mixture of waxes obtained from sheep wool, used as a base for skin creams and ointments intended to
enhance retention of water
Lanolin,
is a mixture of long-chain alkanes
obtained from the processing of petroleum.
- also called paraffin
waxes, resist moisture and chemicals and
have no odor or taste.
mineral wax
beeswax component
candle wax.
