Chapter 9: Lipids and Membranes Flashcards
Draw Palmitic Acid
Should have 16 carbons, saturated. No double Bonds
Draw Oleic Acid
Should have 18 carbons, unsaturated. 1 Double bond at 9th carbon from carboxyllic acid
Draw Linolenic Acid
18 Carbons. 2 Double bonds at 9th and 12th carbon. Omega-6 Fatty Acid
Draw alpha-linoleic Acid
18 Carbons. 3 double bonds at 9th, 12th, and 15th carbon from the carboxyllic acid. Omega-3 fatty acid.
Draw Steric Acid
18 Carbons, saturated. No double bonds
Draw dipalmitylphosphotidylserine
serine is linked to phosphate via its OH group
Draw phosphatidylcholine
choline has 3 methyl groups attached to a positively charged N
Draw phosphatidylserine
serine is linked to phosphate via its OH group
Draw phosphatidylglycerol
glycerol like its own backbone.
Do lipids form polymers?
no, they tend to aggregate and associate together via non-covalent interactions (hydrophobic interactions)
How are fatty acids classified?
by the nature and length of their hydrocarbon chains
What aggregate type do fatty acids form?
micelles- they are amphiphathic because of the COOH and then the non polar R chain
What state is the hydrophillic group of a fatty acid in at physiological ph?
at ph 7.0, the carboxyllic acid is deprotonated
What is the function of a fatty acid?
they serve as intermediates in metabolism and as building blocks for other lipids
do fatty acids play a role in energy storage? Why or why not?
no. their amphipathic nature makes them susceptible to forming micelles due to hydrophobic interactions, thus acting as a soap in the body and dissolving molecules in the body
How would you increase the melting point of a fatty acid?
increase the chain length by increasing the number of carbons. Increase the saturation
How would you decrease the melting point of a fatty acid?
decrease the chain length, and increase the number of double bonds (increase degree of unsaturation). makes the fatty acid more liquidy.
What formation is the an unsaturated lipid in ?
cis
Which unsaturated fatty acid would have a higher melting point? Cis or Trans? Why?
Trans fatty acids have a higher melting point because they can stack more easily than cis fatty acids, allowing them to be solid.
How are fatty acids usually numbered?
starting from the carboxylic acid/carboxylate ion
What’re the two essential fatty acids?
alpha-linolenic fatty acid (w3) and linoleic acid (CLA, w-6)
What type of lipids makes up fats and oils?
triacylglycerols
Difference between fat and oil
fat=solid at room temp
oil=liquid at room temp
What makes up a triacyl glycerol
glycerol and three fatty acid chains held together via ester linkages
what is the suffix of a triacylglycerol?
“oyl”
What is the function of a triacylglycerol? What part of its structure allows it to perform its task?
Energy storage. Unlike fatty acids and other lipids that are polar, the carboylate group on the triacylglycerol is capped with the glycerol head, rendering it non polar and non-amphipathic. Because of its nature, it does not form micelles and can be safely stored in adipose cells without interacting with other portions of the cell.
Further more, since its structure renders it nonpolar, it can be stored anhydrously; unlike carbs and proteins, it can be stored dry, not with water.
Lastly, it provides lots of energy because it holds three long fatty acid chains that are highly reduced (often saturated).
What makes up a glycerophospholipid?
Glycerol+ two free fatty acids+ phosophatidic acid
Are glycerophosphlipids amphipathic? Where would you find one?
they are amphopathic because they have non polar carbon chains and a polar phosphate group that is not capped by the glycerol head. You would find a glycerophospholipid in a membrane.
Which glycerophospholipid does not participate in hydrogen bonding?
glycerophospholipids that contain a phosphtidylcholine chain will not participate in Hbonding because the nitrogen is saturated with carbon.
What makes up a sphingolipid? Where would you find this type of lipid?
ceramide with a head group (varies depending on type of sphingolipid). Membrane lipids, also found in myelin sheath
What is a sphinogmylein lipid
Ceramide+ phosphocholine or phosphoethanolamine. Makes up plasma membrane
Is sphingomyelin ionic or nonionic?
ionic because of it’s phosphate group
On a cerimide, what holds the acyl group?
amide linkage/bond
What is a cerebroside lipid? Is it ionic?
type of sphingolipid. Ceramide + sugar on the head group. Nonionic.
What is a Ganglioside? What is their function
ceramide + complex oligosaccharide, type of sphingolipid, used as a surface membrane lipid for cell-cell recognition.
What type of disease is a result of ganglioside breakdown?
neurological deterioration. Tay-Saches disease.
What makes up a wax ester? what are their characteristics?
A wax ester is made up of a fatty acid and a fatty alcohol held together by an ester linkage.They are often hard and insoluble. They are highly reduces and often used as some sort of structural support. (bees wax).
What is an isoprenoid? What about their structure makes them different than the rest of the lipids?
an isoprenoid is a lipid made of 5 carbons with double bonds that are trans instead of cis. They also have distinguishable methyl projections.
What are the functions of isoprenoid? What does it make up?
1) Ubiquinone; made up of isoprenoids, functions in the electron transport chain.
2) fat soluble vitamins : A, D, K, E
3) cholesterol: weakly amphipathic, many uses in membrane, made of a sterol with 3 OH groups and an isoprenoid
What does Vitamin A do? what happens when there is a deficiency? what role does it play in FASD?
Vitamin A (retinol) in important in vision. Retinol typically gets oxidized to retinoic acid. Retinol (vitA) also plays a role in skin repair, which is why it promotes youthfulness. In FASD, the alcohol competes with the oxidation of retinol process, which is why there is a chance that babies with FASD are born blind.
What does Vitamin D do? what happens when there is a deficiency?
Vitamin D is actually a hormone, but is an isoprenoid derivative. Contains a sterol+isoprenoid. enhances mineral absorption, meaning its plays a role in bone development. people with not enough vitamin D develop rickets
What does Vitamin E do? what happens when there is a deficiency?
acts as an anioxidant, and protects unsaturated lipids from oxidation. Quenches free radicals, therefore it reduces wrinkles and aging.
What does Vitamin K do? what happens when there is a deficiency?
plays a role in blood coagulation.
How does Warfarin work?
it is a competitive inhibitor of vitamin K, preventing blood coagulation. It works as a blood thinner.
What type of lipids make up membranes?
Amphipathic lipids
Would you find triacylglycerol in a membrane?
probs not as much because it is not amphipathic
What three kinds of lipids are in membranes?
sphingolipids, glycerophospholipids, cholesterol
What kind of interactions allow membranes, liposomes and micelles to form?
hydrophobic effect allows membrane formation with hydrophobic tails hiding and hydrophilic heads facing outwards.
What type of lipids are favored during the formation of liposomes?
amphiphiles; sphingolpids and glycerophospholipids
not too much cholesterol because they are only weakly amphipathic
What is a liposome
a lesser biological membrane-only is a lipid bilayer. no proteins or anything.
What kind of shaped lipid do bilayers and liposomes favor?
cylindrical shaped amphiphiles
What kind of shaped lipid do micelles favor?
cone shaped. large polar head and skinner non polar tail.
define steroid
a hormone synthesized by cholesterol, contains 4 fused rings.
What is transverse diffusion?
transfer of a lipid molecule across a bilayer. Very slow/rare process.
What facilitates transverse diffusion in biological membranes?
flippases
What is lateral diffusion
movement of lipids on the same plane. They do not flip. this happens all the time and is really fast.
Define transition temperature
the temp where lipids change state from liquid crystal to gel like solid.
What happens if temp is below transition temp
membrane loses fluidity- becomes very ordered “gel like solid”
What happens if temp is above transition temp?
membrane becomes really fluid and flimsy “liquid crystal”
How could you increase the transition temperature?
increasing chain length. Increasing the degree of saturation (no double bonds)
How would you lower the transition temperature?
decrease the chain length. Add more double bonds, increase the degree of unsaturation.
Where would you find an organism with short fatty acid chains with lots of double bonds?
in a cold temperature environment. The unsaturation of the chains prevents tight packing, and allows the membrane to stay fluid under colder conditions.
What role does cholesterol play in bilayers? can a membrane be made out of pure cholesterol?
Cholesterol cannot form a bilayer by itself, but it can be incorporated into one because it is weakly amphipathic..
Function: broadens the transition temperature by acting as a fluidity buffer
@ Warm temps: decreases membrane fluidity be preventing tons of movement amongst the straight fatty acid chains.
@ cold temps: increases fluidity by preventing the linear chains from tight packing/solidifying
Are lipid membranes permeable to ions? what can lipid membranes/liposomes allow to pass through?
only small uncharge molecules can pass through, like O2, CO2, etc.
charged, polar, large molecules, or ions cannot pass through due to the lipid membranes nonpolar nature.
What is a biological membrane composed of?
1) Amphipathic lipids,
2) proteins (integral/external/lipid linked proteins)
3) carbs
T/F: leaflest of a biological membrane will be identical.
False: each face of the membrane has a different environment and thus different structure and components and proteins. The leaflets are asymmetric.
In terms of lipid movement, what does the fluid mosaic model mean?
means that membrane lipids engage in both lateral and transverse diffusion
Can proteins undergo transverse diffusion? Wb lateral diffusion?
No; yes but slowly.
How is an integral protein associated with the membrane bilayer? how would you remove an integral protein?
they are embedded in the protein. the amino acids that are within the bilayer are non polar. The protein is associated via hydrophobic interactions. They are difficult to remove unless you destroy the membrane via detergents.
Is an integral protein stable in aqueous solution?
No. it has a hydrophobic component- it wants to be in fat.
How is a peripheral protein associated with the membrane bilayer? how would you remove a peripheral protein?
they are typically on the surface of a protein. They are electrostatically bonded, or participate in Hbonding. Bc they are on the surface of the membrane, they are often stable in water and therefore will be happy to be removed. Can be removed via enzyme or simple wash with ionic substance, such as sodium chloride.
How is a lipid linked protein associated with the membrane bilayer? how would you remove a lipid linked protein.
tethered to the membrane via COVALENT BONDS. tightly bound so often characterized as an integral protein. also stable in aqueous solution. can be released via enzyme activity.
How does a statin drug treat hypercholestrolemia?
it inhibits HMG-CoA reductase, which make malevenoate, which is a cholesterol precursor.
Linoleic acid is converted into _____acid
arachidonic acid
alpha-linolenic acid is converted into ____acid
eicosapentanoic acid
arachidonic acid and eicosapentanoic acid make ______ via enzymes lipoxygenase and cyclooxygenase
eicosanoids
What’re the two types of eicosanoids and which omega fatty acid do they stem from?
1) Pro inflammatory/ pro-aggregatory: eicosanoids formed by arachidonic acid, from linoleic acid.
aids in cell-cell recognition
2) Anti-Inflammatory/Inhibit Platelet Aggregation: formed by eicosapentanoic acid, alpha-lin acid.
also aids in membrane components.
Which triacylglycerol would yield more energy via oxidation: 3 chains of linolenic acid or 3 chains of stearic acid?
3 chains of stearic acid because it is more reduced. It does not have any double bonds, there are more bonds and electrons to oxidize
Which glycerophospholipid head groups can form hydrogen bonds?
Everything besides Choline. The nitrogen is bonded to 3 methyl groups; regardless of pH it won’t deprotonate- it has no protons! Has no capacity to bond with anything else because of methyl groups
Why can cultured cells survive in the abcense of linoleic acid, but animals cannot?
linoleic acids produce arachidonic acids, which produce eicosanoids that are used in intercellular communication. Cultured cells do not participate in intercellular communication, and thus do not need linoleic acid.
A bacteria culture that typically survives at 20 degrees celsius is placed in an environment at 30 degrees. What changes would the bacteria make to their membrane lipids?
*to increase transition temperature, they need to start synthesizing longer chains with less saturation.
The less double bonds the better; double bonds decrease the melting point, and decrease the transition temperature, rendering the membrane too liquidy
Do membranes in antarctic fish have longer and/or saturated FAs compared to tropical fish?
No. Increasing chain length and saturation increases the melting point of the membranes-the point where the membrane is at liquid state. Membranes in antarctic fish need the capacity to maintain fluidity at lower temperatures, thus, their fatty acid chains need to be shorter and more unsaturated (more double bonds)
what type of lipid is the primary building block for synthesis of molecules like cholesterol or ubiquinone?
isoprenoid/isoprene
What about their structure is the reason free fatty acids cannot form bilayers? what do they form instead?
They are conical shaped- they have too wide a polar head and a skinny non-polar tail. Bilayers favor cylindrical lipids, like glycerophospholipids or sphingolipids. Free fatty acids instead form micelles.
