Lipids chem Flashcards
LIPIDS: BIOLOGICAL FUNCTION 9
Storage of Energy, Insulation from environment, Water Repellant, Buoyancy control and acoustics in marine mammals, Membrane Structure, Cofactors for Enzymes, Signaling molecules, Pigments, Antioxidants
Classification Lipids 7
Fatty Acids, Waxes, Triglycerides, Phospholipids and Glycolipids, Steroids, Ecosanoids, Membranes
Eight Major Categories of Biological Lipids
Fatty Acids, Glycerolipids, Glycerophospholipids, Spingolipids, Sterol Lipids, Prenol lipids, Saccharolipids, Polyketides
2 major categories based on structure and function:
Lipids that contain fatty acids (Complex lipids)
Lipids that do not contain fatty acids
Two major categories based on their reaction thru
saponification:
Saponifiable lipids
Nonsaponifiable lipids
Saponifiable lipids types 2
Simple lipids
Complex lipids
are the building blocks of many lipids.
Fatty Acid
Saturated Fatty Acid General Formula
CH3(CH2 )nCOOH
Necessary for specific biochemical functions and
must be supplied in the diet.
Essential fatty acids
Two nomenclature systems are used to identify the
length and double bond in the fatty acid
Delta Numbering, Omega Numbering
fatty acids that are essential nutrients
Omega-3 fatty acid
Two types of unsaturated fatty acids
Omega-3, Omega-6
Omega 3 Fatty Acid benefits in human body
reduce the risk of cardiovascular disease by
decreasing blood clot formation, blood triglyceride
levels, and growth of atherosclerotic plaque.
precursor for the synthesis of
prostacyclin, which inhibits clumpingof
platelets and thus reduces clot formation.
EPA
one of the major fatty acids in the
phospholipids of sperm and brain cells, as well
as in the retina; it has also been shown to
reduce triglyceride levels, although the
mechanism is not understood.
DHA
Seems to reduce the incidence of
cardiovascular disease, however it is not clear
whether it acts alone or because it is the
precursor of DHA and EPA
ALA
Also an essential fatty acid, required for the
synthesis of arachidonic acid,
Linoleic acid
are precursors of prostaglandins
that exhibit anti-inflammatory effects
Omega 3 FA
are precursors to prostaglandins
that have inflammatory effects.
Omega-6 FA
Decreases as the chain length increases.
Solubility
Decreases as the chain length decreases. Decreases as the number of double bonds increases.
Melting Point
Have straight –chain structures that allow
their molecules to fit close together and form
strong attractions.
Saturated FA
form by partial dehydrogenation of unsaturated fatty acids.
Trans fatty acids
Are esters composed of three fatty acids
joined to the trihydroxy alcohol, glycerol.
Triglycerides or triacylglycerols (TAG)
The advantage of fats over polysaccharides:
Fatty acids carry more energy, Fatty acids carry less water
if the reacting fatty acid molecules are not all identical,
Mixed Triacylglycerol
is a triester formed from
the esterification of glycerol with three identical
fatty acid molecules.
Simple Triacylglycerol
Current recommended amounts are: total fat
intake in calories:
- Monounsaturated fat
- Polyunsaturated
- Saturated fats
15%
10%
< 10%
Bad Fats vs. Good fats
o Saturated fats
o Monounsaturated fats
o Trans-monounsaturated fats
o Polyunsaturated fats
o Omega 3 and 6 are important “good fats”
= “bad fats”
= “good fats”
= “bad fats”
= both good and bad
= are important “good fats”
Heart SatFat Graph
Canola Oil
Safflower Oil
Sunflower Oil
Corn Oil
Olive Oil
Soybean Oil
Margarine, tub*
Peanut Oil
Margarine, stick*
No heart SatFat Graph
Cottonseed Oil
Solid Vegetable shortening
Lard
Palm Oil
Butter
Palm Kernel Oil
Coconut Oil
Physical Properties of Tags:
Pure fats and oils are….
colorless, tasteless, and odorless.
The characteristic colors, odors, and flavors
associated with lipids are imparted to them by
foreign substances
They are poor conductors of heat and electricity and therefore, serves as _______
excellent insulators for the body.
CHEMICAL PROPERTIES OF TAGs 5
Hydrogenation
Halogenation
Hydrolysis
Oxidation
Saponification
Addition of H2 to double bonds of unsaturated fatty acids in lipids, converting them to single bonds of saturated fatty acids.
HYDROGENATION
Complete hydrogenation gives a __________,
whereas the partial hydrogenation of a liquid vegetable
oil changes it to a _____________.
very brittle product; soft, semisolid fat.
Addition of water to ester bonds of lipids in
the presence of strong acids or digestive
enzymes called ________
Lipases; HYDROLYSIS
Addition of halogen across double (=) bond, this increases degree of saturation
- A test for unsaturation
HALOGENATION
Reaction of lipids with a strong base (alkaline hydrolysis) to give glycerol and salts of the fatty acids (called _____).
SAPONIFICATION; soaps
Products of the reaction are (Saponification)
- An alcohol
- An ionized salt which is a soap.
- Soaps have a long uncharged hydrocarbon tail
- Also have a negatively charged carboxylate group at end.
- Form micelles that dissolve oil and dirt particle.
The salts of fatty acids are also called _____,
and are considered ______. meaning they
have a part that is _______ along with
a part that is __________.
Soaps; amphipathic; very hydrophobic; very hydrophilic
They do not form insoluble products with hard
water.
Detergents
Double bonds in triacylglycerols are subject to
oxidation with oxygen in air (an oxidizing agent)
－Leads to C=C breakage
OXIDATION
Fat and oil develops a disagreeable odor caused by hydrolysis and oxidation.
Rancidity
Under moist and warm conditions, hydrolysis of the ester linkages occurs, liberating the volatile acids (butyric or caproic acids). Microorganisms present in the air furnish the enzyme (lipases) that catalyze the process.
Hydrolytic rancidity
Occurs in triglycerides containing unsaturated fatty acid
Oxidative rancidity
Are compounds added to foods in very small amounts (0.01–0.001%) to suppress rancidity. They have a greater affinity for oxygen than the lipid to which they are added and thus function by preferentially depleting the supply of adsorbed oxygen. Some naturally occurring
antioxidants used in the food industry are _____, ______, ________
Antioxidants; BHT, BHA, Vitamin E
An ester of a saturated fatty acid and a long-chain alcohol, each
containing from 14 to 30 carbon atoms.
Waxes
Found in the surfaces of leaves and stems and
serve to protect the plant from dehydration and
from invasion by harmful organisms.
Plant Waxes
also serve as protective coatings; found on the
surface of feathers, skin, and hair and help keep these surfaces soft and pliable.
Animal Waxes
is a mixture of a large number of lipids, including esters of triacontanol, and a long-chain alkane hentiacontane.
Beeswax
Is a semipermeable structure that
defines the boundaries of all cell types
CELL MEMBRANE
It is composed of lipids, proteins and
carbohydrates
Fluid Mosaic Model
Semi-fluid composition allows
lateral diffusion
The cell membrane has roles:
- Controlling the flow of ions into and out of the cells
- Uptake of nutrients and disposal of waste.
- Cell recognition and communication.
The central architectural feature of biological membranes is a
double layer of lipids
TYPES OF MEMBRANE LIPIDS
Phospholipids, Glycolipids, Cholesterol
TWO BACKBONES FOR MEMBRANE LIPIDS
Glycerol
Sphingosine
Primary constituents of cell membranes
GLYCEROPHOSPHOLIPIDS /phosphoglycerides
Is the major component of most eukaryotic cell membranes.
PHOSPHATIDYLCHOLINE
Vinyl ether analog of phosphatidylethanolamine
ETHER LIPIDS: PLASMALOGEN
Aliphatic ether analog of phosphatidylcholine.
ETHER LIPIDS: PLATELETS-ACTIVATING FACTOR
When a fatty acid is attached in amide linkage to the -
NH2 on C-2 of sphingosine, the resulting compound is
a
Ceramide
three subclasses of sphingolipids, which
are all derivatives of ceramide,
- Sphingomyelins
- Glycosphingolipids
- Gangliosides
Ceramide (sphingosine + amide-linked fatty
acid) + phosphocholine attached to the alcohol.
Abundant in myelin sheath that surrounds some nerve cells in animals.
Sphingomyelins
- Contains both a fatty acid and carbohydrate
- Simple sphingoglycolipids are called ______: contains a single monosaccharide unit - either glucose or galactose
- They occur primarily in brain (7% of dry mass)
Glycosphingolipids; cerebrosides
Are glycosphingolipids with two or more sugars, usually D- glucose, D-galactose, or N-acetyl-D-galactosamine.
globosides
are the most complex glycosphingolipids.
Gangliosides
The structure of sugar is determined by an
expression of specific
glycosyltransferases
Individuals with no active glycosyltransferase will have the _______
O ANTIGEN
Individuals with a glycosyltransferase that
transfers an N-acetylgalactosaminegroup
have
A BLOOD GROUP
Individuals with a glycosyltransferase that
transfers a galactose group have
B BLOOD GROUP
Failure to correctly degrade gangliosides results in build-up of lipids in lysosomes, a dysfunction categorized as
“lysosomal storage disorders.”
An example of a Lysosomal storage diseases
Tay-Sachs disease
A lipid whose structure is based on a
fused ring system of three 6 carbon rings and
one 5 carbon ring.
STEROID
A variety of steroid compounds are
formed. These include ___, _____, _____ and _____.
cholesterol, steroid hormones, bile acids and Vitamin D
The most abundant animal steroid.
CHOLESTEROL
Hardening of the arteries
Atherosclerosis
Important Features of Biological Membranes (4)
Membrane Fluidity, Selective Permeability, Self- Healing Capability, Assymmetry
A substance moves across a cell membrane by diffusion from a region of higher concentration to
a region of lower concentration.
Passive 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.
Facilitated transport
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
Proteins involved in active transport are called
Pumps
Are oxidized derivatives of sterols
Steroids
Two major classes of steroid hormones:
Sex Hormones; Adrenocortical Hormones
Sex Hormones (A,B,C)
A. Male sex hormones or Androgens
(Testosterone and Androsterone)
B. Female sex hormones or estrogens
(Estrone and Estradiol)
C. Progestin (Progesterone)
Regulate a variety of metabolic processes.
Adrenocortical Hormones
Adrenocortical Hormones (A,B)
A. Mineralocorticoids (e.g. Aldosterone)
B. Glucocorticoids (e.g. Hydrocortisone and Cortisone)
Act like detergents in the small intestine where they keep the cholesterol in solution and emulsify fats, forming smaller fat globules that are more accessible to the lipases (fat digesting enzymes).
Produced by the liver (from cholesterol), stored in the
gall bladder and secreted into the intestine
BILE SALTS
(80% cholesterol, colored by bile pigments) form when:
- The cholesterol level in bile is too high.
- The concentration of bile salts is too low.
GALLSTONES
Lipid-soluble vitamins
A, D, E, and K
Vitamin D Is Synthesized from
Cholesterol
Is formed from cholesterol by the action of ultraviolet radiation from the Sun.
vitamin D3 (cholecalciferol),
A deficiency of vitamin D can lead to _____, a deficiency of vitamin D can lead to
RICKETS
Are lipids found in the oils of some
plants and flowers that give them their
characteristic odors and colors
TERPENES
Terpenes are composed of two or more sections
containing five carbon conjugated structure
called
ISOPRENE
- Required for the formation of the visual pigment found in the retina of the eye.
- Precursor for other hormones involved in signalling
VITAMIN A; RETINOL
Prevents oxidation of unsaturated fatty acids in
cellular membranes (antioxidant).
VITAMIN E; alpha-tocopherol
Needed in the formation of prothrombin for blood
clotting
Vitamin K: Phylloquinone
- Are arachidonic acid (20:4) derivatives:
- Have profound physiological effects at extremely
low concentrations. - Are hormone-like molecules.
- Exert their effects in the tissues where they are
synthesized. - Usually have a very short “life.”
EICOSANOIDS
Three classes of Eicosanoids
a) Prostaglandins
b) Leukotrienes
c) Thromboxanes
Brief summary of some of the biological processes
- Blood Clotting
- The Inflammatory Response.
- Reproductive System
- Gastrointestinal Tract
- Kidneys
- Respiratory tract.
The most common and important complex lipids are
plasma lipoproteins
The categories of lipoproteins are based on
Density
Four major classes of human plasma lipoproteins:
- Chylomicrons
- Very low density lipoproteins (VLDL)
- Low-density lipoproteins (LDL)
- High-density lipoproteins (HDL)
A human plasma lipoprotein:
- Density, less than 0.95 g/mL
- Produced by the intestine.
- Transport dietary lipid from intestine to other tissues
- The largest lipoproteins.
Chylomicrons
A human plasma lipoprotein:
- Density, 0.95–1.019 g/mL.
- Produced by the liver
- Bind triglycerides synthesized in the liver and carry them to adipose and other tissues for storage.
Very low density lipoproteins (VLDL)
- Density, 1.019–1.063 g/mL.
- Produced from IDL (Intermediate Density Lipoproteins) with loss of Apo C-II.
- Carries cholesterol to peripheral tissues.
- Help regulate cholesterol levels in those tissues
Low-density lipoproteins (LDL)
- Density, 1.063–1.210 g/mL.
- Synthesized by liver and intestine
- Bound to plasma cholesterol
- Transport cholesterol from peripheral tissues
(“reverse transport”) to the liver for removal
High-density lipoproteins (HDL)
The Good Cholesterol; Carry cholesterol from organs
and blood to liver to get rid of it
HDL
CHOLESTEROL LEVELS
- Good Level:
- Border Line:
Good level: below 200 mg/dl (low risk of heart disease).
- Border line: 240mg/dl (if higher at high risk).
Are a structurally and functionally diverse class of molecules that are poorly soluble in water.
LIPIDS
Are the main storage lipids.
Triacylglycerols
Are the main constituents of membranes.
Phospholipids
Play roles in cell recognition.
Sphingolipids
Is both a membrane lipid and the precursor for steroid hormones.
Cholesterol
Some lipids carry signals from _____ and ______
cell to cell and from tissue to tissue.
What are the four types of lipids?
Fatty Acids, Steroids, Oils, Phospholipids, Triglycerides
What is the monomer & polymer of lipids?
- Monomers are glycerol and fatty acids;
- Polymers called diglycerides, triglycerides
Structurally, how do you tell the difference in carbs & lipids?
Structurally, carbohydrates are polymers that exist in different forms such as monosaccharides, disaccharides and polysaccharides. On the other hand, lipid is a nonpolymeric molecule that constitutes a glycerol molecule and three fatty acid chains.
Difference of Saturated and Unsaturated Fats
Saturated Fats are solids at room temp. They are a type of fats that have predominantly single bond between molecules in the fatty acid chain. While, Unsaturated fats are liquids at room temp. They are a type of fats that have double bonds between molecules of the fatty acid acid. Moreover, Unsaturated fats are considered beneficial or healthy fats while Saturated fats are considered unhealthy and bad fats.
