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
if a fatty acid is named “omega-n”, what does this indicate?
- the n is a number which indicates how far from the methyl carbon (AKA omega carbon) a double bond is found
- this is determined by starting with the omega carbon as #1
example: omega-3 fatty acids have a double bond starting from the 3rd carbon
What are the functions of triacylglycerols?
- energy storage
- thermal insulation
- mechanical protection
(within adipocytes)
Where is the energy in triacylglycerols that is used metabolically to produce ATP?
- in the long chains of fatty acids containing many hydrogens
- hydrogens are “burned” with O2in mitochondria to form water and drive the process of oxidative phosphorylation
How much energy do fatty acids have in comparison to carbohydrates?
Why?
approx. 2x the energy per unit mass
b/C both Hs connected to a fatty acid chain are reduced
ex:
FA = H-C-H
but
Carb = H-C-OH
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
What are the common FAs for glycerophospholipids?
– 16:0 or 18:0 at C1
– 18:1 Δ(2) or 20:1 Δ(2) at C2
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 are the molecules with carbs attached to C1 of a sphingolipid?
3 main categories and their respective carbs.
- what is one of their major functions?
Glycosphingolipids
- Cerebrosides - glucose, galactose… muscle/nerve cells
- **Globosides **- neutral oligosacchs…
- Gangliosides - anionic oligosacchs… cell surface
- specify cell identity - responsible for blood grouping
What is the basic structure of sterols?
three 6-membered rings, one 5-membered ring
plus =O or -OH on first 6-C ring
What are some properties of steroid hormones?
- low water solubility
- transported via proteins
- pass through membranes
- both genomic and non-genomic action via intranuclear and perimembranous receptors
