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126 terms

Biochemistry - Unit 4: Chemistry of Lipids

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biocompounds that are soluble in organic solvents
lipids
lipids usually possess at least one of the following 3 structures, what are they?
fatty acid (acyl group)
isoprene
cyclopentanoperhydrophenanthrene (CPPP)
fatty acids contain which functional group?
acyl group
most abundant structural component of lipids
fatty acids
which type of acid is covalently bonded to alcohol?
ester acid
what does the R in R-COOH represent?
R is hydrocarbon chain-minimum 3 carbons
type of fats primarily in animal fats
saturated (SAFA)
SAFA possess only ___ bonds b/t Cs
single
mono-unsaturated (MUFA) fatty acids possess ___ double-bond per molecule
ONE
3-C fatty acid
propionic acid
4-C fatty acid
butryic acid
16-C fatty acid
palmitic acid
18-C fatty acid
stearic acid
20-C fatty acid
arachidic acid
primarily in vegetable oils
poly-unsaturated (PUFA) fatty acids
poly-unsaturated fatty acids possess at least ___ double bonds b/t Cs
2
what are the 2 most commonly seen MUFAs in living tissue?
C16:1;9
C18:1;9
what does each number in C16:1;9 represent?
C16 = number of Cs
1 = number of double bonds
9 = position of double bond
3 alternate ways to annotate C16:1;9
cis-^-9 palmitoleic acid
9-hexadecenoic acid
PALMITOLEIC ACID
3 alternate ways to annotate C18:1;9
cis-^-9 oleic acid
9-octadecenoic acid
OLEIC ACID
2 PUFAs that cannot be synthesized by the human body
LINOLEIC ACID "LA"
ALPHA-LINOLEIC ACID "ALA"
ratio associated with MUFAs
50:50
PUFAs not synthesized in significant amounts; made from the essential fatty acids
CONDITIONALLY essential fatty acids
3 conditionally essential fatty acids
GAMMA-LINOLEIC ACID "GLA"
ARACHIDONIC ACID "AA"
EICOSAPENTAENOIC ACID "EPA"
C number where first double bond occurs (counted BACKWARD... the last C is C1)
Omega (w) number
within the same omega series, a PUFA can be made ___ and with more ___ bonds (enzymes in the body to be discussed later)...but retains same ___ number
longer; double; omega
omega number of linoleic acid
w-6
what is C18:2;9,12?
linoleic acid (LA)
omega number of linoleic acid
w-6
not synthesized by humans; in most vegetable oils: sunflower, safflower, evening primrose seed, corn, peanut, canola, olive
linoleic acid
LA --> ___ --> DGLA --> ___
GLA; arachidonic acid
GLA - C18:3;6,9,12
gamma-linoleic acid
DGLA C20:3;8,11,14
dihomo-gamma-linoleic acid
C20:4;5,8,11,14
arachidonic acid
most abundant PUFA in cell membranes
arachidonic acid
omega number of alpha-linoleic acid
w-3
ALA C18:3;9,12,15
alpha-linoleic acid
not synthesized by humans
in flaxseed oil
small amounts in some nuts, green leafy vegetables, canola, wheat germ, black currant seeds
alpha-linoleic acid
ALA --> ___ --> DHA
EPA
EPA C20:5;5,8,11,14,17
eicosapentanoic acid
DHA C22;6;4,7,10,13,16,19
docosahexaenoic acid
sources of trans-fatty acids
partially hydrogenated margarine
shortening
commercial frying fat
high-fat baked goods
salty snacks
in trans Hs are on ___ ends of a double bond and in cis Hs are on ___ ends of a double bond
opposite; same
DRI recommendations:
first, trans fatty acids are not essential and provide ___ ___ ___ to human health, whether from animals or plants.
second, while both saturated and trans fats increase levels of LDL, cholesterol, trans fats also lower levels of ___ cholesterol-increasing the risk of ___ ___ ___.
the NAS is concerned that dietary trans fatty acids are more ___ with respect to CHD than saturated fatty acids.
supported by a 2006 NEJM scientific review that states from a nutritional standpoint, the consumption of trans fatty acids results in considerable potential ___ but no apparent ___.
no known benefit
HDL; coronary heart disease
deleterious
harm; benefit
fat and oil
triglycerides
lecithin, etc.
phospholipids
carotenoids, vit A, etc.
isoprene lipids
cholesterol, etc.
steroid lipids
sphingomyelin, glycolipids
sphingolipids
eicosanoids, licoprotein, etc.
lipid derivatives
___% of food lipids are triglycerides
90
fat: mainly from ___ sources (mostly SAFA)
oil: mainly from ___ sources (mostly PUFA)
animal; plant
all triglycerides contain fatty acids. fats and oils differ by the ___ ___ they have.
fatty acids
fatty acids differ by number of ___, position, ___, cis vs. trans of ___ bonds
Cs; number; double
exceptions to triglycerides
plant oils with little PUFA
plant oils with little PUFA include which 2 oils?
coconut and olive oils
high in medium-chain fatty acids C10-C14
coconut oil
high in OLEIC acid, a C18 MUFA C18:1,9
olive oil
4 types of phospholipids
phosphatidylcholine
phosphatidylethanolamine
phosphatidylinositol
phosphatidylserine
phosphatidylcholine aka
lecithin
phosphatidylethanolamine aka
cephalin
phosphatidylinositol aka
lipositol
in cell membranes; body's reserve of PUFA
phospholipids
in addition to the 4 types of phospholipids, there are ___
PLASMALOGENS
ether (as opposed to ester) linkage at first C of glycerol; account for ~10% of brain and muscle lipids
PLASMALOGENS
vit A, E, K are all ___ lipids; they are all ___-soluble
isoprenoid; fat
beta-carotene, retinol examples of what?
vit A
2-methyl-1,3-butadiene is an example of what?
isoprene-->isoprenoid lipid
steroid lipids sub-divided into which 6 categories?
cholesterol
glucocorticoids
mineralocorticoids
reproductive steroids
provitamin D
bile acids
steroids which have -OH as primary functional group
STEROLS
CPPP is basic structure of which type of lipid?
steroid lipids
a 27C sterol, implicated in the pathogenesis of atherosclerosis
cholesterol
when a cholesterol forms an ester with a FA, the ester is called a ___ ___
CHOLESTERYL ESTER
___ is the precursor of all other steroids
cholesterol
glucocorticoids: one important physiological function is the stimulation of ___ from ___. examples: ___ (hydrocortisone), corticosterone and ___ (synthetic)
gluconeogenesis; proteins; cortisol; dexamethasone
mineralocorticoids: enhance ___ retention and enhance excretion of ___, ___, and ___. the primary endogenous mineralocorticoid is ___.
Na+; K+,H+,NH4+; ALDOSTERONE
COX
cyclooxygenase
3 reproductive steroids
androgens
estrogens
progestins
male sex steroids
androgens
female sex steroids
estrogens
gestational steroids
progestins
primarily produced by testes. e.g. testosterone and dihydrotestosterone (DHT). testes also make some 17 beta-estradiol (estrogen)
androgens
primarily produced by ovaries. e.g. 17 beta-estradiol and estrone
estrogens
produced by corpus luteum and placenta. e.g. progesterone
progestins
ergosterol (pro-D2 in yeast) and 7 dehydrocholesterol (pro-D3 in human skin) are examples of which type of steroid?
provitamin D
C24 steroids with functional groups -COOH and -SO3H. major ones in human bile are: cholic acid, deoxycholic acid, glycocholic acid and taurocholic acid
bile acids
___ functional groups of bile acids dissociate to become negative ___ ...which bind to positive ions such as ___ or ___ to form bile ___
acidic; anions; K+; Na+; SALTS
vit D is from ___
cholesterol
sphingolipids are lipids that contain ___ as their alcohol component
SPHINGOSINE
2 examples of sphingolipids
sphingomyelins
glycosphingolipids
sphingosine + FA + phosphocholine
sphingomyelins
sphingosine + FA + carbohydrate
glycosphingolipids
3 examples of glycosphingolipids
gangliosides
cerebrosides
sulfatides
compounds derived from lipids or mixtures containing lipids
lipid derivatives
3 examples of lipid derivatives
FAs and eicosanoids and lipoproteins
derived from 20C PUFAs
eicosanoids
2 types of eicosanoids
prostanoids
leukotrienes
3 types of prostanoids
prostaglandins (PG)
prostacylclins (PGI)
thromboxanes (TX)
regulate contraction & relaxation of smooth muscle
prostaglandins (PG)
oppose platelet aggregation
prostacyclins (PGI)
stimulate platelet aggregation
thromboxanes (TX)
from 20C PUFAs + glutathione
leukotrienes
mediate allergic reaction
leukotrienes
complex of lipids (TG, phospholipids, cholesterol esters, free cholesterol) + protein (apolipoprotein, apoprotein, apo)
lipoproteins
PL and Apo outside; TG, CE, and FC inside is characteristic of which structure?
structure of lipoprotein
responsible for transport of lipids
lipoproteins
hydrophobicity
lipids are composed (largely) of Cs and ___
together the C-H bond does not have ___
therefore, they do not form ___ bonds or ___ bonds
so...when lipids are added to water (solvent), they do not ___. they aggregate on top, forming ___ ___
Hydrogens
POLARITY
IONIC; HYDROGEN
mix; 2 layers
amphipathic:
some lipids (e.g. phospholipids) possess O-, ___, or NH4+ at one end and ___ chain at the other
thus, these molecules exhibit both ___ and ___ properties
the hydrophilic ends interact with ___, the hydrophobic ends stay away and ___
results in the formation of ___ (hydrophobic ___ with hydrophilic ___)
PO4 3-; hydrocarbon; hydrophobic; hydrophilic; water; aggregate; micelles; core; surface
formed by 2 layers of amphipathic molecules with hydrophobic tails facing each other
lipid bilayer
basic structure of all membranes; fluid mosaic model
lipid bilayer
breaking and mixing of dietary fat particles for further digestion by enzymes
emulsification
emulsification usually done by ___ ___
bile salts
which one is amphipathic? bile salt or dietary fat?
bile salt
spoilage of lipid foods
rancidity
autooxidation
oxidative rancidity
bacterial hydrolysis
hydrolytic rancidity
in rancidity, ___ bonds of acyl groups are oxidized by ___...accelerated by light and ___
DOUBLE; oxygen; temp.
produces noxious/toxic substances
rancidity
2 examples of noxious/toxic substances produced via rancidity
malondialdehyde (toxic) and short-chain FAs
butter: bacteria produce short-chain FAs-->unpleasant odor
vegetable oils, whole grains, and cereals that have a high content of PUFAs are prone to ___. keep in air-tight, cool dark places
OXIDATION
PARTIAL HYDROGENATION of oils can prevent ___ rancidity, but it causes production of ___ FAs, which increases cholesterol level and risk of ___ ___ ___
oxidative; trans; coronary heart disease
addition of ___ also can be added to help prevent against rancidity. examples are vit E, BHT (butyl hydroxytoulene), BHA (butyl hydroxyanisole)
ANTIOXIDANTS
BHT
butyl hydroxytoulene
BHA
butyl hydroxyanisole
double bonds in FAs of naturally occurring TGs are usually ___ form, which occupies more space
CIS
comparing 2 TGs with the same number of Cs
the one with the most double bonds (___) is ___ dense and appears as liquid at room temp.-->___
the more ___ one is ___ and appears as solid at room temp.-->___
unsaturated; LESS; OIL; SATURATED; DENSER; FAT