LIPIDS Flashcards
Collective term for fixed oil, fats and waxes.
LIPIDS
are biomolecules that are insoluble in water but readily soluble in organic solvents, such as chloroform or acetone
LIPIDS
lipids are classified by their ____
miscibility/immiscibility in water
lipids do not have any common ____
building blocks
Lipids are not defined by a particular functional group, thus they have a ____ of structures and functions.
variety
Lipids contain many ____ C—C and C—H bonds and few polar bonds resulting in their water insolubility.
nonpolar
Are heterogeneous group of compounds (fats, oils, steroids, waxes and related compounds), that are related more by their physical than by their chemical properties.
Lipids
Properties of Lipids
____ to touch, leaves a permanent oily stain on paper;
greasy
Properties of Lipids
____ than water
lighter
Properties of Lipids
When ____, colorless with bland odor and taste;
pure
Properties of Lipids
____ color in fat is due to carotene
yellow
Properties of Lipids
Yellow color in fat is due to
carotene
provitamin A
Properties of Lipids
When ____ strongly, undergoes decomposition forming acrid flammable vapors
heated
Properties of Lipids
whenignited, they burn with a ____ flame.
sooty
- test conducted for lipids
- leaves a permament oily stain on paper
grease spot test
acrid flammable vapors is called
acrolein (propenal)
egg yolk contains, an emulsifying agent
lecitin
lipid soluble vitamins
A D E K
Major Roles of Biological Lipids
They serve as ____ of biological membranes.
structural components
Major Roles of Biological Lipids
They provide energy reserves, predominantly in the form of ____.
triacylglycerols
Major Roles of Biological Lipids
Both lipids and lipid derivatives serve as ____.
chemical messengers
Major Roles of Biological Lipids
____ aid in lipid solubilization.
lipophilic bile acids
Biomedical Importance
Fats are stored in ____
adipose tissue
Biomedical Importance
Fat stored in adipose tissue serves as ____ in the subcutaneous tissues and around certain organs
thermal insulator
Biomedical Importance
Nonpolar lipids act as ____, allowing rapid propagation of depolarization waves along myelinated nerves;
electrical insulator
Biomedical Importance
Lipoproteins occur in both ____ and ____, and also serve to transport lipid in the blood.
cell membrane & mitochondria
Biomedical Importance
stored in adipose tissue serves as thermal insulator in the subcutaneous tissues and around certain organs;
fats
Biomedical Importance
act as electrical insulator, allowing rapid propagation of depolarization waves along myelinated nerves;
nonpolar lipids
Biomedical Importance
occur in both cell membrane and mitochondria, and also serve to transport lipid in the blood.
lipoproteins
- Important dietary constituents
- High energy value
- Contains fat-soluble vitamins and essential fatty acids
lipids
- Are necessary fats that humans cannot synthesize, and must be obtained through diet.
- Are long-chain polyunsaturated fatty acids derived from linolenic, linoleic, and oleic acids.
essential fatty acids
Classification of Based on the “alcohol component”
Ester of fatty acid and low MW monohydric alcohol
simple lipid
Classification of Based on the “alcohol component”
- esters of three molecules of fatty acids plus one molecule of glycerol.
- Found in adipose tissue, butterfat, lard, suet, fish oils, olive oil, corn oil
triglycerides
Classification of Based on the “alcohol component”
ester of fatty acid and glycerol
fats/fixed oil
Classification of Based on the “alcohol component”
ester of fatty acid and high MW polyhydric alcohol
waxes
Classification of Based on the “alcohol component”
butterfat, lard, suet, fish oils, olive oil, corn oil
triglycerides
Classification of Based on the “alcohol component”
beeswax, head oil of sperm whale, cerumen, carnauba oil, and lanolin
waxes
the only vegetable oil that is solid at room temp
cocoa butter
____ can be converted into smaller molecules by hydrolysis
hydrolyzable lipids
- cannot be cleaved into smaller molecules by aqueous hydrolysis
- resistant to hydrolysis
Nonhydrolyzable lipids
head oil of sperm whale contains
spermaciti
expensive oil coming from the sperm whale
ambergris
Hydrolyzable lipids are derived from
fatty acids
Fatty acids are ____ with long C chains of 4-36 (even number) C atoms.
carboxylic acids (RCOOH)
Naturally occurring fatty acids have an ____ number of C atoms.
even
have no double bonds in their long hydrocarbon chains.
saturated fatty acids
have 1 or more double bonds (generally cis) in their long hydrocarbon chains.
unsaturated fatty acids
As the number of double bonds in the fatty acid increases, the melting point ____.
decreases
nomenclature used in unsaturated fatty acids
omega nomenclature
can act as hormones
prostaglandins
melting point of stearic acid
71C
melting point of oleic acid
16C
chemical formula of saturated fatty acids
CnH2nO2
chemical formula of unsaturated fatty acids
CnH2n - (2 no. of db) O2
unsaturated fatty acids with 1 double bond
monounsaturated
unsaturated fatty acids with more than 1 double bond
polyunsaturated
simplified nomenclature
chain length : double bonds
NOMENCLATURE
carboxyl (COOH) carbon will be labeled as
C1
NOMENCLATURE
suffix - unsaturated
enoic acid
NOMENCLATURE
the terminal CH3 is called
omega carbon
Humans require which fatty acid
essential fatty acid
omega-3 linolenic acid
Precursor in the synthesis of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)
omega-3
linolenic acid
PHYSICAL and PHYSIOLOGIC PROPERTIES OF FATTY ACIDS
____ of even numbered carbon fatty acids:
* increases with chain length
* decreases according to unsaturation
melting point
PHYSICAL and PHYSIOLOGIC PROPERTIES OF FATTY ACIDS
containing three saturated fatty acids of 12 C or more is solid at body temperature
▫ 18:2 fatty residues are liquid at body temperature to below 0°C
triacylglycerol
PHYSICAL and PHYSIOLOGIC PROPERTIES OF FATTY ACIDS
must be fluid at all environmental conditions
▫ More unsaturated than storage lipids
membrane lipids
- Derived from eicosa- (20 carbon) polyenoic fatty acids
- Arachidonic acid is the major precursors
eicosanoids
- Are part of a family of biologically active lipids derived from the** twenty-carbon** essential fatty acids or eicosanoids;
- Relates to the products of the cyclooxygenase pathway
- Prostanoic acid as the central structural element
-
Three main groups
▫ Prostaglandins (PGs)
▫ Prostacyclins (PGIs)
▫ Thromboxanes (TXs)
prostanoids
central structural element of prostanoids
prostanoic acid
- behave like lipids but acts as local hormones
- Synthesized from eicosanoic polyunsaturated fatty acids (arachidonic acid) to form cyclopentane ring
- PG1, PG2, and PG3– numbers are based on the double bonds in the side chain
- The letter component identifies the functional groups of the cyclopentane ring
prostaglandins
prostaglandin with keto group in 9th position
PGE
prostaglandin with hydroxyl group in 9th position
PGF
- Cyclopentane ring interrupted with an oxygen atom;
- Its role is in clot formation (thrombosis)
thromboxanes
two major thromboxanes
A2 & B2
- Formed via the lipooxygenase pathway
- Has three (leukotrienes) to four (lipoxins) conjugated double bonds
LEUKOTRIENES & LIPOXINS
a proinflammatory agents and causes bronchoconstriction, thus play a part in asthma
leukotrienes
are esters formed from a fatty acid and a high molecular weight alcohol.
waxes
scientific name of sperm whale
physeter macrocephalus
major component of spermaceti wax
cetyl palmitate
synthetic form of cetyl palmitate
cetyl ester wax
Because of their long nonpolar C chains, waxes are very ____
hydrophobic
beeswax is also known as
yellow wax
Like other esters, waxes are ____ with water in the presence of acid or base to re-form the carboxylic acid and alcohol they came from.
hydrolyzed
- are three esters formed from glycerol and three molecules of fatty acids
- Main storage forms of fatty acids.
triacylglycerol
have three identical fatty acid side chains.
simple triacylglycerols
have two or three different fatty acids.
mixed triacylglycerol
contain only saturated fatty acids; they make up most animal fat and are solids at room temperature. (no double bond)
saturated tricylglycerol
contain at least one unsaturated fatty acid; they make up most vegetable oils and are liquids at room temperature.
unsaturated triacylglycerol
have 1 C=C bond.
monounsaturated triacylglycerol
have many C=C bonds
polyunsaturated triacylglycerol
Increasing the number of double bonds in the fatty acid chain ____ the melting point of the triacylglycerol.
decreases
have higher melting points; they are solids at room temperature.
fats
Fats are derived from fatty acids with ____ double bonds.
few
have lower melting points; they are liquids at room temperature.
oils
Oils are derived from fatty acids having a ____ of double bonds
larger number
are used to build cell membranes, insulate the body, and store energy for later use.
fats
It is recommended that no more than ____% of a person’s caloric intake should come from lipids.
20 - 35%
A high intake of ____ is linked to heart disease.
saturated triacylglycerol
Saturated fats stimulate ____ synthesis, which can lead to cholesterol plaques building up inside arteries. (atherosclerosis)
cholesterol
lower the risk of heart disease by decreasing the level of cholesterol in the blood.
unsaturated triacylglycerol
Triglycerols formed from ____ are very helpful in lowering the risk of heart attack.
omega-3 fatty acids
if the double bond of the unsaturated triacylglycerol is ____, the beneficial effect is lost.
trans
- primarily synthesized instead of naturally occurring
- act like saturated fats and increase the cholesterol levels in the blood.
trans fats
Triacylglycerols are hydrolyzed with water in the presence of ____, ____, or ____ (in the body).
acid, base, or enzymes
Humans store ____ as triacylglycerols in adipose cells below the surface of the skin, in the breast area, and surrounding internal organs.
energy
The number of adipose cells is ____
constant
weight gained or lost causes adipose cells to ____ or ____, but not decrease or increase in number
swell or shrink
To metabolize triacylglycerols for energy, the esters are hydrolyzed by enzymes called
lipases
- Esters of fatty acid, alcohol and another compound.
- has more than 1 component
compound lipid
- Fatty acid and alcohol plus a phosphoric acid residue
- Frequently have nitrogen-containing bases and other substituents (glycerophospholipids, sphingophospholipids)
phospholipids
PHOSPHOLIPIDS
the alcohol is glycerol
glycerophospholipids
PHOSPHOLIPIDS
the alcohol is sphingosine
sphingophospholipids
fatty acid and sphingosine plus carbohydrate.
Glycosphingolipids
are lipids that contain a P atom
phospholipids
Two common types of phospholipids
phosphoacylglycerols
sphingomyelins
- Main lipid constituents of membrane
- Derivatives of phosphatidic acid
phospholipids
Phosphate is esterified with the ____ of a suitable alcohol
-OH
intermediate in the synthesis of triacylglycerols
Phosphatidic acid
- are the main component of most cell membranes.
- Structurally, they resemble a triacylglycerol, except the third fatty acid has been replaced with a phosphodiester bonded to an alcohol.
Phosphoacylglycerols
The two fatty acid side chains form____ that lie parallel to each other.
2 NONPOLAR TAILS
The phosphodiester end of the molecule is a
charged or polar head
One of the main types of phosphoacylglycerols
cephalin
cephalin is chemically known as
phosphatidylethanolamine
The second of the main types of phosphoacyl-glycerols
lecithin
lecithin is chemically known as
phosphatidylcholine
- Phosphoacylglycerol containing choline
- Most abundant phospholipids of the cell membrane and represent a large proportion of the body’s store of choline
- present in egg yolks
- can be used as lipid lowering
phosphatidylcholine
lecithin
important in nervous transmission, as acetylcholine, and as a store of labile methyl group
choline
- Effective surface-active agent
- Major constituent of the surfactant preventing adherence, due to surface tension, of the inner surfaces of the lungs.
- Absence: Respiratory distress syndrome
dipalmitoyl lecithin
phosphatidyl in tissues
phosphotidylserine
inositol has stereoisomer called
myoinositol
Precursor of second messenger
PHOSPHATIDYLINOSITOL
important constituent of the cell membrane phospholipids and cleaved into diacylglycerol and inositol triphosphate (internal signals or second messenger)
Phosphatidylinositol 4,5-biphosphate
- bisphosphatidyl glycerol
- Is an important component of the** inner mitochondrial membrane**, where it constitutes about 20% of the total lipid
- It serves as an insulator and stabilizes the activity of protein complexes important to the electron transport chain
CARDIOLIPIN
- Are intermediates in the metabolism of phosphoglycerols
- Important in the metabolism and interconversions of phospholipids (lysophosphatidylcholine)
- Found in oxidized lipoproteins and can promote atheroschlerosis
LYSOPHOSPHOLIPIDS
- do not contain a glycerol backbone, they have a sphingosine backbone instead.
- do not contain an ester; their single fatty acid is bonded to the backbone by an amide bond.
Sphingomyelins
- 10% of the phospholipids of the brain and muscle
- Resemble phosphatidylethanolamine (ether linked)
- Alkyl radical is an unsaturated alcohol
PLASMALOGENS
- Found in large quantities in brain and nerve tissues
- Yields fatty acid, phosphoric acid, choline, and a complex amino alcohol, sphingosine
SPHINGOMYELINS
the coating that surrounds nerve cells, is rich in sphingomyelins.
myelin sheath
- Sphingosine plus amino acid
- Structure found in glycosphingolipids
CERAMIDE
- Distributed in every tissue of the body
- Nervous tissues (brain)
- Plasma membrane – cell surface carbohydrates
glycolipids
glycolipids is also known as
GLYCOSPHINGOLIPIDS
- Major glycolipids in animal tissues
- Ceramide + sugar
Glycosphingolipids
Are complex glycosphingolipids derived from glucosylceramide that contain in addition one or more molecules of a sialic acid
GANGLIOSIDES
Major sphingolipid of brain & other nervous tissue, C24 fatty acids
GALACTOSYLCERAMIDE
principal sialic acid found in human tissues.
NEURAMINIC ACID
- contains ceramide, one molecule of glucose, one molecule of galactose and one molecule of NeuAc (neuraminic acid)
- The simplest gangliosides in tissues
GM3
product of simple and compound lipid upon hydrolysis.
derived lipid
- occur in plant and animal foods
- also exhibit in complex forms with other substances
- obtained from hydrolysis of fats
- usually contains an even number of carbon atoms and are straight chain derivatives
fatty acids
Acylglycerols, cholesterol, and cholesteryl ester are uncharged, so are termed
neutral lipids
are a group of lipids whose carbon skeletons contain several fused rings
steroids
the most prominent steroid, is synthesized in the liver and found in almost all body tissues.
cholesterol
It is obtained in the diet from many sources, including meat, cheese, butter, and eggs.
cholesterol
a molecule that is synthesized in one part of an organism, which then elicits a response at a different site.
hormone
Two important classes of steroid hormones
sex hormones
adrenal cortical steroids
female sex hormones
estrogen & progestins
male sex hormones
androgen
estrogens that control development of secondary sex characteristics, regulate the menstrual cycle, and are made in the ovaries.
estradiol
estrone
- called the “pregnancy hormone”
- it is responsible for the preparation of the uterus for implantation of a fertilized egg.
progesterone
- are androgens made in the testes.
- They control the development of secondary sex characteristics in males.
testosterone
androsterone
- Synthetic androgen analogues that promote muscle growth
- They have the same effect as testosterone, but are more stable, so they are not metabolized as quickly.
- They have come to be used by athletes and body builders, but are not permitted in competitive sports.
- Prolonged use can cause physical and psychological problems.
anabolic steroids
Three examples of adrenal cortical steroids
aldosterone
cortisone
cortisol
regulates blood pressure and volume by controlling the concentration of Na+ and K+ in body fluids.
aldosterone
serve as anti-inflammatory agents, which also regulate carbohydrate metabolism.
cortisone
cortisol
Prolonged use of these steroids can have undesired side effects, including bone loss and high blood pressure.
adrenal cortical steroids
Adrenal Cortical Steroids
a synthetic alternative, has similar
anti-inflammatory properties
prednisone
are organic compounds required in small quantities for normal metabolism and must be obtained from the diet.
vitamins
Vitamins are either ____ solube or ____ soluble
water or fat
four fat-soluble vitamins that are found in fruits, vegetables, fish, liver, and dairy products.
A D E K
fat soluble vitamins are stored in
adipose cells
- found in liver, fish, and dairy products, and is made from β-carotene.
- It is needed for vision and for healthy mucous membranes.
- deficiency causes night blindness and dry eyes and skin.
vitamin A
- can be synthesized from cholesterol.
- It can be obtained in the diet from many foods, especially milk, and helps regulate Ca and K metabolism.
- deficiency causes rickets (bone malformation).
vitamin D
- Precursor of vitamin D2
- Occurs in plants and yeast
- It is turned into viosterol by UV light, and is then converted into ergocalciferol (a form of Vitamin D)
- Acquires antirachitic properties when irradiated with UV light
- A component of fungal cell membranes, serving the same function that cholesterol serves in animal cells
ERGOSTEROL
- an antioxidant, protecting unsaturated side chains in fatty acids from unwanted oxidation.
- Deficiency causes numerous neurological problems, although it is rare.
vitamin E
regulates the synthesis of clotting proteins (prothrombin), and deficiency of this leads to excessive or fatal bleeding.
vitamin K
two types of eicosanoids
prostaglandins
leukotrienes
are very potent compounds, which are not stored in cells, but rather** synthesized in response to external stimulus**.
eicosanoids
Unlike hormones they are local mediators, performing their function in the environment in which they are synthesized.
Prostaglandins and Leukotrienes
are carboxylic acids that contain a five-membered ring and have a wide range of biological activities.
prostaglandins
- are responsible for inflammation
- also decrease gastric secretions, inhibit blood platelet aggregation, stimulate uterine contractions, and relax smooth muscles.
prostaglandins
PROSTAGLANDINS
relieve pain and inflammation by blocking the synthesis of these molecules.
Aspirin and ibuprofen
two different cylcooxygenase enzymes responsible for prostaglandin synthesis called
COX-1 & COX-2
involved in the usual production of prostaglandins.
COX-1
responsible for additional prostaglandins in inflammatory diseases like arthritis.
COX-2
inactivate both COX-1 and -2, but increase risk for stomach ulcer formation.
NSAIDS
Drugs sold as Vioxx, Bextra, and Celebrex block only the____ enzyme** without affecting gastric secretions**.
COX-2
Asthma is characterized by chronic inflammation, so ____ to reduce this inflammation are commonly used.
INHALED STEROIDS
are molecules that contribute to the asthmatic response by constricting smooth muscle of the lung.
LEUKOTRIENES
New asthma drugs act by blocking the synthesis of ____, which treat the disease instead of just the inflammation symptoms.
LEUKOTRIENE C4
Not steroids, but synthesized like cholesterol
POLYPRENOIDS
participates in respiratory chain in
mitochondrion
UBIQUINONE
takes part in glycoprotein synthesis by transferring carbohydrate residues to asparagine residues of polypeptide
DOLICHOL
rubber, camphor, fat soluble- Vit A, D, E & K and -carotene (provitamin A).
ISOPRENOID
- Lipids exposed to oxygen (Auto-oxidation).
- A chain reaction providing a continuous supply of free radicals.
- Effects of iclude:
– deterioration of food (rancidity)
– damage of tissue (cancer, inflammation, atheroschlerosis and aging) caused by free radicals containing methylene-interrupted double bonds
LIPID PEROXIDATION
Catalyzed in vivo by heme compounds and by lipoxygenases (platelets and leukocytes)
PEROXIDATION
products of auto-oxidation
formed from cholesterol
OXYSTEROLS
products of auto-oxidation
prostanoids
Isoprostanes
- Control and reduce lipid peroxidation
- for food are propyl gallate, BHA, BHT
ANTIOXIDANTS
ANTIOXIDANT
lipid soluble
VIT E
ANTIOXIDANT
water soluble
VIT C
URATE
reduce the rate of chain initiation.
* Catalases and Peroxidases
* glutathione peroxidase (reacts with ROOH)
* Selenium
* EDTA, DTPA (Chelators of metal ions)
PREVENTIVE ANTIOXIDANTS
ANTIOXIDANTS
trap superoxide free radicals
SUPEROXIDE DISMUTASE
ANTIOXIDANTS
lipid phase trap ROO radicals
VIT E
Contain predominantly nonpolar groups plus a polar
group.
* Molecule is partly hydrophobic and hydrophilic.
* Include fatty acids, phospholipids, sphingolipids, bile
salts, and cholesterol.
* Oriented at oil: water interfaces with the polar group
in water phase and the nonpolar group in the oil
phase.
* Basic structure of biologic membranes (bilayer).
AMPHIPHATIC LIPIDS
