LIPIDS Flashcards
What is lipid?
-molecules that contain hydrocarbons
-main component of the structure n functions of living cells
list the general functions of lipids
Main molecule for energy storage (triglyceride/triacylglycerol)–
lipids are non polar.
Polar lipids are important components of the biological membrane–
forms lipid bilayer.
Steroids
Chlorophyll, carotenoid and retinol.
As fat soluble vitamins, A, D, E and K.
As electron transport carriers in the chloroplast and mitochondria
(ubiquinone (UQ or CoQ) and plastoquinone (PQ)).
As signal molecules – prostaglandins
what are the classifications of lipids?
- Fatty acids (FA)
- Triacylglycerol / triglyceride (TG) / neutral lipid
- Phospholipid / glycerophospholipid
- Sphingolipid
- Waxes
- Steroids / cholesterol
- Terpenoids / terpenes
describe fatty acids
- Long chain carboxyl acids (4C – 30C).
- Has long aliphatic chain – not branched.
- One end has a methyl group and the other a carboxyl group.
- Amphiphatic (two opposite properties) – the tail is hydrophobic
while the head is weakly hydrophilic. - In nature they are esterified to glycerol – because they are
poisonous if free. - Most have even number of carbons (16C-22C) with single C-C
bonds - Can be saturated (no double bonds) or unsaturated (1 – 6 double
bonds). - Mostly (>50%) are unsaturated.
- Double bonds are in the cis configuration (not trans) and
unconjugated (linked by a methylene unit , – CH2
-). - Fatty acids with <12 carbons are soluble in water.
- They are soluble in dilute NaOH/KOH to yield soap;
(the hydrophobic end of FA is called the omega end while the hydrophilic end is called delta end. read FA from omega end)
Examples of Unsaturated Fatty ACID?
-FA is divided into two : monounsaturated fatty acid (MUFA) & polyunsaturated fatty acid (PUFA)
example of PUFA
1) omega 3
alpha-linolenic acid:
-plant-omega 3
-dietary precursor for omega-3 eicosapentaenoic acid (EPA), dicosapentaenoic acid (DPA) & docosahexanoic acid (DHA)
-can be found in seafood
2) omega 6
arachidonic acid
linoleic acid :
-found in oil, corn, beans, meat, eggs, soybeans
example of MUFA
1)omega 9
oleic acid :
-found in canola oil/olive oil
what is trans fat?
-trans fat is the common name for unsaturated fat with trans-isomer FA. (straight molecule)
-may be MUFA or PUFA but NEVER SATURATED
effects of trans fat consumption?
-increases risk of coronary heart disease by raising LDL cholesterol & lowering levels of HDL.
describe triacylglycerol/ triglyceride (TG)
-found in fats n oils in animals n plants
-made up of 1 glycerol + 3 fatty acids
-insoluble in water
-FA triesters of glycerol
-act as energy storage
-can be simple/ mixed triacylglycerol
-when hydrolyzed with alkali, will yield soap
-commercially important for saponification
-substitues butter into PUFA margarines thru hydrogenation (double bonds > single bonds)
-leads to some cis double bonds > trans double bonds (may increase in blood cholesterol)
describe phospholipid/glycerophospholipid
-main lipid of biological membranes
-made up of a polar group, glycerol, phosphate and 2 fatty acids
-have hydrophilic head and hydrophobic tails
phospholipids/ glycerophospholipids is also known as?
phophoglyceride/ glycerol phosphatide
examples of polar groups that can be esterified to the phosphate group of phospholipid?
choline, ethanolamine, serine, inositol, glycerol etc
what happens when phospholipid + choline?
phosphotidyl choline
phospholipid + serine
phosphotidyl serine
phospholipid + ethanolamine
phosphotidyl ethanolamine
what replaces glycerol that produces sphingolipids?
sphingosine = an 18C alcohol
what happens when sphingosine + fatty acid?
ceramide, attach to C2
what happens when ceramide + phosphocholine/ethanolamine at 1-OH goup ?
sphingomyelin is formed. (found in myelin sheath of nerve cells)
what happens when ceramide + beta-galactose/glucose at the C1 where there is an OH group?
cerebroside is formed
what happens when ceramide + oligosaccharide at the C1 where there is an OH group?
ganglioside is formed
importance of glycosphingolipids/glycolipids-
-cell-cell recognition
-nerve impulse transmission
-tay-sachs disease in small children is where ganglioside GM2 accumulate resulting in early death
-
what is waxes?
-simple lipids
-esters of long chain alcohols + long chain FAs
-has one weakly polar end
-FAs in waxes is usually saturated
-highly insoluble
-found in animal skins/ surface of certain fruits
examples of waxes
-carnauba wax is from a palm tree in brazil (used for car polish)
-lanolin : wax from wool used in pharmaceutical industry - easily absorbed by human skin
-spermaceti - wax found in whales, made up of palmityl alcohol + palmitate
describe steroid
-important group of terpenes
what are the 5 hormones included in steroids?
- androgens (male sex characteristics ie. testosterone)
- estrogens (female sex characteristics ie. estradiol)
- progestrin (for period n pregnancy ie progesterone)
- glucocorticoid & mineralocorticoid
- bile acids
example of glucocorticoid
cortisol : regulate lipid,carbs n protein metabolism
functions of mineralocorticoid
regulate K+, Na+ and Cl- balance in tissues
example of bile acids
cholic acid : helps in absorption of fats in the intestines
what is cholesterol?
a very important n most common steroid
describe the structure of cholesterol
-4 non aromatic rings (3 six membered rings + 1 five membered ring)
-1 hydroxyl group
-1 double bond
-1 side chain
describe the cholesterol found in blood
-found as lipoprotein complexes (classified according to density)
1. chylomicrons (lowest density)
2. VLDL (very low density lipoprotein)
3. LDL (low density lipoprotein)
4. HDL (high density lipoprotein)
5. IDL
function of chylomicrons?
transport cholesterol & dietary TG from intestines to liver
functions of VLDL?
transports cholesterol esters (CE) and TG form liver to tissues (transfers more TG than CE)
function of IDL?
same as VLDL (TG>CE)
function of LDL
same as VLDL but transports CE > TG
functions of HDL?
transports cholesterol from tissues to liver
what can lipoprotein dysfunction cause?
-artherosclerosis (hardening of arteries) - yellow precipitation of cholesterol esters in the arterial walls
-it is progressive and can contribute to the formation of blood clots
-usually occurs in coronary artery
