chem lab - lipids Flashcards
hydrophobic isoprenoids
A, D, E, K
are PUFAs
-must be provided in our diet because EFAs cannot be biosynthesized
EFAs
- Fatty-acid related :
fatty acid/prostaglandins, fatty acid esters, sterol esters, lipoconjugates
- Hydrolyzable/saponifiable:
fatty acid esters, sterol esters, lipoconjugates
-aliphatic, acyclic, unbranched
fatty acids
fatty acid synthesis in humans:
liver and lactating mammary glands
most naturally occurring FA contain odd or even no. of C atoms
EVEN
- no C=C
- CnH2n+1 COOH
- ___anoic acid
saturated
- CnH2n-1COOH
- ____enoic acid
unsaturated
– natural configuration of C=C
Cis configuration
- introduces a kink, allowing a bend
- bend disrupts alignment of lipid → semi-fluid
Cis configuration
2 EFAs to humans
- Linoleic acid –
2. Linolenic acid
precursor of arachidonic acid
linoleic
– precursor of PGs
-becomes essential if linoleic acid is missing
Arachidonic acid
– alkali salts of Fa
- formed by saponification
- amphipathic
- nonpolar + dirt, polar + water (micelle)
- Soaps
- Halogens add to C=C via
AE
– resistant to oxidation outside the body
saturated FA
slowly but spontaneously oxidized by oxygen in air
-becomes rancid (formation of short chain aldehydes)
USFA-
-derived from linoleic acid (or arachidonic acids) forming eicosanoids
PROSTAGLANDINS
-cyclopentane ring, 2 side chains, carboxyl group in one side chain
PROSTAGLANDINS
-participate in wound-healing process
PROSTAGLANDINS
PAIN MEDIATORS
PROSTAGLANDINS
-esters formed between a fatty acid (CA) and glycerol (trihydric alcohol)
Acyglycerols or glycerides
-3 Fatty acids + glycerol
TRIGLYCERIDES
-neutral fats or neutral oils
TRIGLYCERIDES
-most widespread
TRIGLYCERIDES
-most abundant lipids in animals (function: food store)
TRIGLYCERIDES
Hydrolysis of tripalmitin or 1,2,3-tripalmitoyl-sn-glycerol
- 1 mole of glycerol
* 3 moles of palmitic acid
Hydrolysis of palmitostearoolein or 1-palmitoyl-2-stearoyl-3-oleoyl-sn-glycerol
- 1 mole glycerol
- 1 mole palmitic acid
- 1 mole stearic acid
- 1 mole oleic acid
Hardening of oils is due to what reaction
-hydrogenation of C=C → saturated compounds
Drying oils s due to what reaction
-action of O2 in air forms hydroperoxides
-composed of an alcohol + diacylgycerol or sphingosine
phospholipids
-phospholipids with glycerol
phosphoglycerides/glycerophosphatides/phosphoacylglycerol
all phosphoglycerides contain
phosphatidic acid
backbone of phosphoglycerides
phosphatidic acid
– alcohol-soluble, acetone-insoluble
lecithin
-most abundant phosphoglyceride
lecithin
- white waxy substance
- used as an emulsifier
- predominantly phosphatidyl choline
lecithin
4nry amine alcohol
Choline-
Hydrolysis of lecithin
- 2 moles FA
- 1 mole phosphoric acid
- 1 mole choline
- 1 mole glycerol
– alcohol-insoluble, acetone-insoluble
- abundant in nerve and brain tissues
- mixture of phosphatidyl ethanolamine (predominant) or phosphatidyl serine
Cephalin
Hydrolysis of cephalin
- 1 mole ethanolamine or serine
- 2 moles FA
- 1 mole phosphoric acid
- 1 mole glycerol
- derivatives of perhydrocyclopentanophenanthrene
steroids
true terpenes
steroids
-synthesized in living systems from isoprene via squalene
steroids
-steroids with one or more OH groups (alcohols)
Sterols
– 27 C atoms
-2ndary alcohol
cholesterol
-derived from B-squalene (triterpene)
cholesterol
-major constituent of gallstone from which it was first isolated
cholesterol
-major sterol in animal tissues
cholesterol
- Component of cell membrane
2. Precursor of bile acids, steroid hormones, vitamin D
cholesterol
– plays a central role in regulation of body’s cholesterol
Liver
– plasma cholesterol in esterified form
-hydrolysable
Cholesteryl esters
-hydrolysis of cholesteryl esters
1 mole cholesterol, 1 mole FA
-control 2o sex characteristics, reproductive cycle, growth and development of accessory reproductive organs
- Sex hormones
produces testosterone (androgen that stimulates spermatogenesis and development of male 2o characteristics) in Leydig cells, stimulated by LH
-testis
produce estrogen (menstrual cycle, 2o sex characteristics) and progesterone (secretory phase of uterus and mammary glands, nidation, maturation of fertilized ovum)
-ovaries:
-control water and electrolyte balance, carbohydrate and protein metabolism
- Adrenocorticoid hormones
secreted when ACTH is stimulated
-increased gluconeogenesis, anti-inflammatory action, protein breakdown
Cortisol –
- secretion induced by Na/K ratio and by angiotensin
- function: stimulates renal reabsorption of Na and excretion of K
Aldosterone
- Vitamin D – lipid soluble, nonpolar, hydrophobic
- derived from isoprenoids or terpenoids
vit D
Vit D2
ergocalciferol
Vit D3
cholecalciferol
-most toxic of all vitamins, slowly metabolized
vit D
watery mixture of organic and inorganic compounds, contain lecithin and bile salts
-Bile:
pKa = 6, not fully ionized
bile acids
provide the only mechanism for cholesterol excretion
bile salts
emulsifier
bile acids, soap, lecithin
- multiples of isoperene units
- where most of the plant’s pleasant odors come from
TERPENOIDS OR ISOPRENOIDS
– a triterpene
- precursor of cholesterol
- all trans-configuration
Squalene or β-squalene
- collective term for retinol, retinoic acid, retinal, β-carotene (tetraterpene)
- found in green vegetables, fruits, eggs
- stored in liver
vit A
- function: essential for vision, growth and reproduction
- deficiency: night blindness, xerophthalmia
vit A
– visual pigment consisting of retinal and opsin
Rhodopsin
rhodopsin consists of (2)
retinal and opsin
- found in vegetable oils, egg
- naturally occurring tocopherols
Vitamin E
most active tocopherol
alpha-tocopherol
-function: natural antioxidant
Vitamin E
-least toxic of fat-soluble vit
Vitamin E
- in cabbage, cauliflower, spinach, egg yolk
- stored in liver
- absorbed in presence of bile acid
Vitamin K
parent cpd of Vitamin K
menadione, vit K3
- function: Koagulations vitamin
- large doses: haemolytic anemia, jaundice
VIT K
-first isolated from the brain
SPHINGOLIPIDS
-2nd most abundant class of lipids
SPHINGOLIPIDS
-found in cell membrane of nerve and brain tissues
SPHINGOLIPIDS
-backbone compound of sphingolipids
ceramide
phospholipids with sphinosine
Sphingosine Phosphatides –
– abundant in brain and nerve tissues
-zwitterionic, amphipathic
Sphingomyelin
– accumulation of sphingomyelin in large amounts in brain, liver, spleen
Niemann-Pick disease
Hydrolysis of sphingomyelin:
•
1 mole fatty acid
• 1 mole sphingosine
• 1 mole phosphoric acid
• 1 mole choline
- sphingolipids with carbohydrates, without phosphorus
- primary OH group is hydroxylated
Sphingosine glycosides or glycosphingolipids
sphingolipid found in white matter of brain
Cerebroside or galactosyl ceramide –
– glucose replaced galactose
Gaucher’s disease
Hydrolysis of cerebrosides
- 1 mole of D-galactose
- 1 mole sphingosine
- 1 mole FA
– also found in brain
-OH of C3 is esterified to a sulphate group
Cerebroside sulfates/Sulfatides
– glycosphingolipids with sugar sialic acid
Gangliosides
number of grams of I2 absorbed by 100 g lipid sample
Iodine number-
– number of mg KOH needed to neutralize free fatty acids or fatty acids released as result of hydrolysis in 1 g lipid sample or fatty acid released
Acid Value
-↑ acid number, ______
↑tendency to be rancid
-measure of acidity, measure of the tendency to become rancid
Acid Value
– number of mg KOH required to saponify the ester in 1 g of lipid sample
Ester Number
Acid Number + Ester Number =
Saponification Number
number of mg KOH required to neutralize free fatty acids or fatty acids released as a result of hydrolysis and to saponify esters contained in1g lipid sample
Saponification Number-
-lipid constant also called Koetts Dorfer
Saponification Number-
