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
