fats and fatty acids Flashcards
LIPIDS: CLASSIFICATION
what are htey made of
composed of C, H and O • ratio of O to C's and H's lower than with CHO • relatively insoluble in H2O • soluble in nonpolar solvents – e.g., ether, chloroform, benzene • energy releasing nutrient
A. Simple Lipids
- Fatty acids (FAs)
- Neutral fats - monoglycerides (MG)
- diglycerides (DG)
- triglycerides (TG)
[triacylglycerols] - Waxes - esters of FAs with ↑ alcohols
a. Sterol esters: e.g,, cholesterol esters
b. Non-sterol esters: e.g., Vit A esters, etc
B. Compound Lipids
- Phospholipids
a. Phosphatidic acids
e. g., lecithin, cephalins
b. Plasmalogens
c. Sphingomyelins - Glycolipids - carbohydrate containing
- Lipoproteins - lipids associated with ptn
C. Derived Lipids
derivatives formed from A and B • possess general properties of lipids • soluble in organic solvents – e.g., ether, chloroform, acetone • fat-soluble vitamins • corticosteroid hormones • coenzyme Q (electron transport)
STRUCTURE AND FUNCTION
FATTY ACIDS (FAs)
Basic unit of lipids is FA
- building block of other lipids
defined by # of Cs and presence of double bonds
H3C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C=O
|
OH
nonpolar(omega end), hydrophobic polar, hydrophillic
(lengthening end)
No double bonds (DB): Saturated
With double bonds (DB): Unsaturated - 1, 2, 3 or 4 DBs
- cis or trans (cis common)
even # Cs in FA: naturally occurring (plants/animals)
odd # Cs in FA: occur is small amts in food
Physical Properties:
Melting point of a FA (and TG containing it) will ↓ with:
1. the shorter the chain
2. the higher the degree of unsaturation i.e., # of DBs
Hydrogenation:
- UFA → SFA ( liquid → solid )
- adding H+ to DBs (less rancid, ↓ [O])
- cis UFA → SFA → cis UFA or trans UFA
- used for “margarine” production
- trans FAs are UFAs but act like SFA
i.e., solid, no EFA properties, ↑ blood cholesterol
- consumer beware (food labels)
Fatty Acids: Names & Sources
If chain is short: Short Chain (Volatile) FA
2:0 = acetic (GI fermentation)
3:0 = propionic (GI fermentation)
4:0 = butyric (butter, GI)
If chain is medium length (6-14C): Medium Chain FA
12:0 = lauric
14:0 = myristic
Fatty Acids: Names & Sources
If chain is long (16-20C): Long Chain FA 16:0 = palmitic (common) 18:0 = stearic (common) 20:0 = arachidic There are fatty acids with C>20 Very Long Chain FAs
One double bond = monounsaturated (MUFA)
H3C-C-C-C-C-C-C-C-C=C-C-C-C-C-C-C-C-C=O | OH 16:1 = palmitoleic 18:1 = oleic (olive) [common]
2 or more double bonds = polyunsaturated (PUFA)
H3C-C-C-C-C-C=C-C-C=C-C-C-C-C-C-C-C-C=O | OH "ω" or "n" delta (Δ) 18:2(9,12) 18:2Δ9,12 18:2ω6 18:2n6 = linoleic 18:3(9,12,15) 18:3Δ9,12,15 18:3ω3 18:3n3 = α-linolenic 20:4n6 = arachidonic 20:5n3 = eicosapentaenoic
3 families of unsaturated FAs:
- n-3 = ω3 = delta 9,12,15
18: 3n3 → 20:5n3 (eicosapentaenoic [EPA] fish)
- classified as “essential” (α-linolenic)
- 20:5n3 precursor to “eicosanoids” (PG3)
- hypolipidemic, antithrombotic effects
- 22:6n3 (docosahexenoic acid - fish)
- membrane phospholipid, cerebrum
3 families of unsaturated FAs:
- n-6 = T6 = delta 9,12
18:2n6 → γ-linolenic (18:3n6)→ 20:3n6 → 20:4n6
seeds (18:2n6 linoleic ) → 20:3n6 → 20:4n6 → PG2
└→ PG1
animals (20:4n6 arach) → PG2
- classified as “essential” (linoleic)
3 families of unsaturated FAs:
- n-9 = delta 9
16:0 → 18:0 → 18:1 (oleic) → ≠ 18:2n6
→ ≠ 18:3n3
- animals can convert (18:0 → 18:1→ 20:3)
- no known function of 20:3
Eicosanoids:
arachidonic acid (20:4n6)* eicosatrienoic acid (20:3n6) eicosapentaenoic acid (20:5n3)* ↓ [Ox] prostaglandins (P) thromboxanes (T) leukotrienes (L) * more common in food
Prostaglandins
18:2n6 → PG1 & PG2 20:4n6 → PG2 18:3n3 → PG3
- 20 Cs, 5 C ring, # DBs, small structural difference
e.g., PGD, PGE, PGF, PGI, PGG, PGH
Eicosanoid Function:
- immune fn effects
- gastric secretions
- vasodilators (↓ BP) or vasoconstrictors,
- ↑ smooth muscle contraction
- ↓ or ↑ platelet aggregation
NEUTRAL FATS
Triglycerides (TG) = Triacylglycerols
TG = glycerol + 3 FAs (ester bonds)
- simple TG = same FAs / mixed TG = different FAs
- “high energy” storage form of body fat
- adipose TG → free FA → body tissue → OX
- 95% of dietary fat as TGs
- TG exist as fats (solids) or oils at room temp
- depends on FA composition (oil = SCFAs and ↑ DBs)
Diglycerides (DG) = glycerol + 2 FAs
Monoglycerides (MG) = glycerol + 1 FA
- negligible in tissues
- intermediate in some metabolic reactions
e.g., lipases - digestion, hydrolyse TG
- component of other lipids
- in food, emulsifying agents
STEROLS AND STEROIDS
steroid = 4-ring hydrocarbon structure sterol = monohydroxy alcohol of steroid e.g., - cholesterol synthesized in animals - other sterols found in plants e.g., ergosterol) Cholesterol - NB component of cell membrane - precursor for other steroids cholesterol + FA = cholesterol ester
PHOSPHOLIPIDS
5% of fat intake
– food emulsifiers, plants & animals
1. glycerol + 2 FAs [1,2 Cs] + (Pi + base [3 C])
base = choline (lecithin), inositol etc
2. sphingomyelins (FA + Pi + sphingosine)
- myelin sheath of nerve tissue
- polar structures (hydrophillic properties)
- chylomicrons
- cell and organelle membranes (regulator of passage)
GLYCOLIPIDS (GL)
backbone of GL (Ceramide = FA + sphingosine)
- GL contains no Pi
Cerebrosides - ceramide + monosaccharide (MS)
(GLU,GAL)
Gangliosides - ceramide + oligosaccharide
(MS derivative)
- structure of cell membranes
- “recognition markers” on exterior of membrane
- cell identity (NB for immune system)
LIPOPROTEINS (LP)
transport form of lipids in blood - 5 main classes: chylomicrons very low density lipoptn (VLDL) intermediate density lipoptn (IDL) low density lipoptn (LDL) high density lipoptn (HDL) Plus: FFA bound to albumin
omega-3 vs omega 6
3 makes the 3
6 makes the 1 and 2
giglycerides
glycerol + 2 FAs
Monoglycerides (MG)
glycerol + 1 FA
NEUTRAL FATS
Diglycerides (DG) = glycerol + 2 FAs Monoglycerides (MG) = glycerol + 1 FA - negligible in tissues - intermediate in some metabolic reactions e.g., lipases - digestion, hydrolyse TG - component of other lipids - in food, emulsifying agents-
STEROLS AND STEROIDS
steroid = 4-ring hydrocarbon structure sterol = monohydroxy alcohol of steroid e.g., - cholesterol synthesized in animals - other sterols found in plants e.g., ergosterol) Cholesterol - NB component of cell membrane - precursor for other steroids cholesterol + FA = cholesterol ester
steroid
steroid = 4-ring hydrocarbon structure
sterol =
monohydroxy alcohol of steroid (added OH on the molecules)
e. g., - cholesterol synthesized in animals
- other sterols found in plants
e. g., ergosterol)
cholesterol ester
cholesterol + FA
PHOSPHOLIPIDS
(95% as triglycerides) 5% of fat intake (from cell membranes)
– food emulsifiers, plants & animals
1. glycerol + 2 FAs [1,2 Cs] + (Pi + base [3 C])
base = choline (lecithin(eggs)), inositol etc
2. sphingomyelins (FA + Pi + sphingosine)
- myelin sheath of nerve tissue
- polar structures (hydrophillic properties)
- chylomicrons
- cell and organelle membranes (regulator of passage)
the phosphate group is the hydrophylic part, (2 fa and a phosphate group and a pase
sphingomyelin
ceramide with a choline(base) with a phosphate group
GLYCOLIPIDS (GL)
- backbone of GL (Ceramide = FA + sphingosine)
- GL contains no Pi
Cerebrosides - ceramide + monosaccharide (MS)
(GLU,GAL)
Gangliosides - ceramide + oligosaccharide
(MS derivative) - structure of cell membranes
- “recognition markers” on exterior of membrane
- cell identity (important for immune system)
ceramide
sphingogosine with faty acid
Cerebrosides
- ceramide + monosaccharide (MS)
GLU,GAL
Gangliosides
- ceramide + oligosaccharide
MS derivative
LIPOPROTEINS (LP)
5 main kinds
wont ever ask us to draw but know what theyre made up of,
- transport form of lipids in blood
- 5 main classes: chylomicrons (82% triglyceride, 7% phospholipids, 2% cholesterol9% protein)
very low density lipoptn (VLDL) (54% tryglyceride, 18%phospholipds, 22% cholesterol, 7% protein- made in the liver to transport extra fats from liver from diet to tissue, high in phospholipids because made in liver tot ransport to other tissues to rejevenate cell membranes, high in cholesterol from liver (made there)liver making fats to destribute to rest of body)
intermediate density lipoptn (IDL)( 31% triacylglyceride, 22%…)
low density lipoptn (LDL) (9% triacylglecerides, 23% phospholipid, 47% cholesterol, droped off tri to the adipose tissue - the “bad” cholesterol, 21% protein )
high density lipoptn (HDL)( 3% tri, 28% phospholipids, 19% cholesterol, 50% protein - rejevinate cell membrane and pick up LDL cholesterol
Plus: FFA bound to albumin (very dense lipoprotein, no apoprotein coding)
outer layer of protein,
improve HDL by physical activity, MUFAS,
chylomicron half life is really short just from intestine to the liver- about 1 hour, LDL stick around
MAJOR FUNCTIONS OF LIPIDS
IN THE BODY:
- As a compact storage of NRG (TG)
- As thermal insulator (TG in adipose tissue)
- As a “cushion” to support internal organs
• e.g., kidneys (TG in adipose) - As a constituent of membranes of all cells and cell organelles
• PL, GL, sterols - As a constituent of myelin sheath
• complex/derived fats, e.g., cerebrosides - Precursors to essential compounds (FAs)
e.g., eicosanoids: PG, thromboxane, leucotriene
18:2n6→→→18:3n6 → 20:3n6 (→PG1) → 20:4n6 → PG2
18:3n3 → 20:4n3 → 20:5n3 →PG3
MAJOR FUNCTIONS OF LIPIDS
B. AS A FOOD COMPONENT:
- High energy value (9 kcal or 38 kJ per gram)
- As a source of essential fatty acids (EFAs)
- As a medium for fat-soluble vitamins and a
requisite for their digestion and transport in the
blood from absorption - Provide flavour and aroma to food
- High satiety value (delay gastric emptying)
Dietary Sources & Health Implications
• Foods containing MCFAs (10-14 Cs):
coconut, palm kernel (“tropical oils”), MCT oil
- liquid at room temperature
- SFA but not long chain
- ↓ intake since these ↑ serum cholesterol,
especially LDL
NOT PART OF MICELLE- WHICH GOES TO CHYLOMICRON TO THE LYMPHATIC SYSTEM- PPL WITH BAD LYMPH SYSTEM TAKE THESE FATS FOR ENERGY
Dietary Sources & Health Implications
• Foods containing long chain (LC) SFA:
dairy, lard, tallow (“animal”), cocoa
SFA: suggest ↓ to <10% energy
- solid at room temp
Dietary Sources & Health Implications
• Foods containing MUFA:
olive, canola, peanut
MUFA do not raise serum cholesterol
- use to replace SFA
- extra fat as MUFAs (Mediterranean Diet)
good SUBSTITUTE FOR SATURATES
Dietary Sources & Health Implications
• Foods containing PUFA as n-6:
seed oils: corn, soy, safflower (linoleic 18:2n6,9)
18:2n6,9 → (desaturation) → 18:3n6,9,12 (GLA)
- primrose, borage (supplement)
• Foods containing PUFA as n-3:
18:3n3,6,9 = α-linolenic
canola 10%, linseed, soy 7% (vegetables n-3)
20:5n3 = eicosapentaenoic (EPA)
fish: fatty fish or fish liver oils
PUFAs and MUFAs
Want M&P/S ratio > 1 - so can ↓ S and ↑ M&P without ↑ total fat - too much P not good → eicosanoids problems
more monos and pufas than saturated
prostaglandins- heart health, can be vasoconstrictor if too much because participate in platelets- dont go crazy on the 6s
DIGESTION AND ABSORPTION
pancreatic lipase breaks them down
4 interacting factors are essential for normal fn of the
intestines in fat absorption:
1. secretion of hydrolytic enzymes from pancreas to break
ester linkages of TG
2. release of detergents (bile salts) in the bile to emulsify
fats and breakdown products
3. uptake of digestion products into mucosal cells (villi) of SI
4. conversion of digestion products into particles for
transport from MCs to lymph system & blood
DIGESTION AND ABSORPTION
Failure:
fat in the faeces (i.e., steatorrhoea)
- diarrhoea
- H2O & electrolyte loss
- ↓ absorption of nutrients
- fat soluble vitamins
- starvation
DIGESTION
LIPOLYSIS:
hydrolysis by pancreatic enzymes called lipases
- in duodenum, - lipids mix with secretions
- emulsions form
- lipases act
TG → 2-MG + 2FAs → Na salts (TG/DG ≠ absorbed)
DIGESTION
BILE SALTS AND MICELLES:
bile salts: - detergents (hydrophilic & hydrophobic) - formed by [O] of cholesterol in liver - "mixes" with lipids (↑ surface area) - form emulsions → lipase attack - part of micelles → absorption (enterohepatic circulation)
micelles: - bulky hydrophilic ends outside (aqueous)
- narrow hydrophobic ends inside
- smaller than emulsions
- absorbed by mucosal cell of SI
ABSORPTION
of bile salts
- Micelles (MG and FFAs) absorbed into MC
- glycerol, SCFAs, MCFAs absorbed directly
- do not require to be part of micelle
- absorbed into MC → blood - MG and FFAs reesterified → TG
- requires nrg (FA activated to acyl-CoA deriv) - TG, cholesterol, chol esters, PLs, fat sol Vits
→ stabilized by surface layer of ptn and PLs
- lipid droplet discharged from MC
- chylomicron (CM) - CM enter lymphatics → blood (thoracic duct)
- Circulating CM → lipoptn lipase → FAs
+ glycerol
- after meal, ↑ FA → adipose (↑ insulin)
- also FAs → ↑ other body tissues
- glycerol / CM remnants taken up by liver
- “clearance” of CM = ½ time < 1 h in humans
chylomicron is composed of
phospholipids, cholesterol, protein, triacylglyceride (made from fatty acids, monoacylglycerol)
albumin
direct absorption of short chian free fatty acids
METABOLISM
IN LIVER
IN LIVER
1. SCFAs → portal circulation (via plasma albumin) → liver → FA [O]
2. bile salt (BS)
portal circulatn → liver → BS pool → bile duct → SI →
recycling: enterohepatic circulation
3. other lipids enter liver via the hepatic artery
1. CMR (eg, sterols) → blood → membrane receptors
2. Adipose → FFAs → blood (via albumin) → FA [O]
where do bile salts go
not part of chylomicron- goes to lipid from portal vein
LIPID METABOLISM: LIVER
- hepatic cells play central role in lipid metabolism:
1. FA [O] (exogenous lipids)
2. FA synthesis (endogenous lipids from glu)
3. biosynthesis of cholesterol (and bile salts)
4. formation of phospholipids (of blood plasma)
5. formation of lipoproteins
6. regulatory role in storage of fats in tissues
(fat storage in liver is small < 1% of mass) - regulatory role of liver fails: fatty liver
e.g., toxicity (ie, EOH)
7. production of ketone bodies (alternative nrg)
2 types of fatty liver disease
non-alcoholic liver disease,
cirhosis
- FATTY ACID OXIDATION
• in “fasted state”, FAs important nrg source
– liver priority: glycogen → glu → oblig glu users
• compact fuel (> nrg produced)
• lipids consist mainly of C & H:
– [O] involves consumption of»_space; O2
– Thus, > ATP production
