Lipid Structures & Theory Flashcards
Palmitic Acid
CH3–(CH2)14–COOH
most common saturated fatty acid in nature
Stearic Acid
CH3–(CH2)16–COOH
Palmitoleic Acid
9-C16:1
omega-7
Oleic Acid
- main constituent of olive oil
9-C18:1
omega-9
Linoleic Acid
9,12-C18:2
omega-6 polyunsaturated
Linolenic Acid
specifically alpha-linolenic, the omega-3 version
9,12,15-C18:3
Arachidonic Acid
importance?
5,8,11,14-C20:4
omega-6 polyunsaturated
- very important as a signaling molecule > creates prostaglandins, thromboxanes, and leukotrienes
In general, what is a lipid?
organic molecules containing fatty acids or a steroid nucleus
What are the 4 types of lipids that contain fatty acids?
- Waxes
- Triacylgycerols
- Glycerophospholipids
- Prostaglandins
Describe what can be assumed about a lipid structure from its name using eicosapentaenoic acid as an example.
**eicosa **- denotes 20 carbons total
penta-enoic - denotes 5 “-enes” or double bonds
- no information about the location of the double bonds is given here, but would be indicated with numbers preceding the name
How can double bonds’ locations be specified in a prefix of a fatty acid name?
(Δn)
so an FA with double bonds at carbons 5, 8, and 11 (starting from the COOH end) would contain the prefix:
(Δ5,8,11)
What is the general strucuture of a triglyceride?
- a glycerol with three fatty acids replacing the Hs of its 3 hydroxyl groups
- the H of the FAs carboxyl is also removed to bind with glycerol
- the binding of the FA carboxyl to the glycerol hydroxyl forms an ester bond
(an ester is a central carbon double bonded to an oxygen and single bonded to an R group and another oxygen with a second R group)
What is the general structure of a diglyceride (AKA diacylglycerol)?
Same as a triglyceride, but one of the glycerol’s hydroxyls remains unchanged
What is an ester bond?
- formed between COOH and OH groups
C double bonded to O, single bonded to R1 and OR2
What are prostaglandins?
- eicosanoic signaling lipids derived from arachidonic acid via COX enzymes
- regulate inflammation, among many other functions
- formed by creation of 5-C ring in middle of 20-C chain (on C-8 and 12)
- targeted by NSAIDs (COX inhibitors)
- include prostacyclins (prostaglandin I2) which inhibits platelet activation and vasodilates
What are thromboxanes?
- eicosanoid derivatives of prostaglandins
- 6C ring with ether (R-O-R’)
- vasoconstrictive, hypertensive platelet-aggregating agent
What are leukotrienes?
- eicosanoid inflammatory mediators
- first found in leukocytes, but produced in many immune cells
- trigger contractions in bronchiole smooth muscle, thus influence asthma and allergies
- contain no ring, but have epoxide (a 3 atom ring with O)
What are the 3 important eicosanoid groups to know?
- prostaglandins
- thromboxanes
- leukotrienes
What are waxes?
How do their physical properties differ from other lipids?
Where are they in the body?
- simple esters of long fatty acids (-COOH) and long alcohols (-OH)
- have higher melting points
- make up hydrophobic coatings on skin and in ears, prevent maceration of fetus within womb
What are glycerophospholipids?
Why is the phosphate specifically located on a certain carbon of the backbone?
- main compononents of biological membranes
- glycerol with 2 FAs and phosphate on C3
- glycerol-3-phosphate not 1, because glycerol is prochiral
Phosphatidic Acid
z group is just H
phosphatidyl ethanolamine
found where?
also called?
- z group is ethanol with amine grp
- specifically found on the inner layer of the lipid bilayer
- abundant in brain/nerves
- AKA Cephalin
phosphatidylcholine
found where?
also called?
- choline is the z group
- found in outer layer of lipid bilayer + in pulmonary surfactant, abundunant in brain + nerves
- AKA lecithin
phosphatidylserine
where is it found?
what does it do?
- serine is Z group
- held on inner layer of cell membrane by flippase
- during apoptosis, flippase stops holding it and its flip to the outer layer to signal macrophages
phosphatidyl-inositol
where is it?
- inner cell membrane
phosphatidylglycerol
where is it found?
- found in pulmonary surfactant
What lipid constitutes about 20% of the inner mitochondrial membrane?
Cardiolipin
- glycerophospholipid with phosphatidyl-glycerol as its Z group
- in other words 2 phosphatidic acids with glycerol between them
- this means it has 4 FA attached… 2 for each glycerol
What are ether lipids?
examples?
- lipids in which at least one C of glycerol is bonded to an alkyl chain via an ether (-O-) bond
- similar to triglycerides/glycerophospholipids but long chain alcohols replaces the FAs
- plasmalogen (anti-ox, signaling, membrane dynamics
- platelet activating factor (platelet agg., inflammation, etc… shown below)
Sphingosine
where is it found?
- found in various sphingolipids in cell membranes
- important in signaling as well
(looks like a glycerol with middle OH subbed by amino and 3rd H subbed by 15-C w/ double bond on first C)
Ceramide
where is it found?
- found in cell membranes, contribute to sphingomyelin, etc.
- involved in signaling
(sphingosine with an acyl on the amine)
Sphingomyelin
- where are they found?
- found in myelin sheath and other cell membranes
- can also have phosphoethanolamine
(ceramide with a phosphocholine group on the bare OH)
Cholesterol
Cortisol
aldosterone
Estradiol
Testosterone
Progesterone
Cholic Acid
Prostaglandin E2
another name
function?
dinoprostone
- signals labour, induces fever, stimulates bone resorption
What is the basic structure of sterols?
three 6-membered rings, one 5-membered ring
plus =O or -OH on first 6-C ring
