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

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