Week 4: Lipids

In which solvents do lipids have high solubility?

Nonpolar solvents

Where do lipids have low solubility?

Water or polar solvents

When it comes to fungi and bacteria, why do fungi produce lipase?

-Fungi don’t like bacteria because they compete with bacteria for food, so they produce lipase to create a dead zone

True or False: Lipases hydrolyze the fatty acids off the glycerol backbone

True

How does lipase hydrolyze fatty acids?

Lipase specifically hydrolyzes the ester bonds of triglycerides to release free fatty acids and glycerol-containing products.

What is the general structure of a glycerophospholipid?

• Glycerol backbone (3-carbon molecule)

• Two fatty acid tails attached to carbons 1 and 2 by ester bonds

• Phosphate group attached to carbon 3

• Polar head group attached to the phosphate (e.g., choline, ethanolamine, serine, inositol)

What does a saturated fatty acid consist of?

a straight carbon chain consisting only of single C-C bonds; all carbons are saturated with the maximum number of hydrogens

What does an unsaturated fatty acid consist of?

a carbon chain containing at least one C=C double bond; double bonds create bend (kinks)

How do the double bonds in unsaturated fatty acids make the cell membrane more fluid?

the double bonds create kinks, preventing tight packing of the phospholipid tails

What causes saturated fatty acids to pack tightly?

-The hydrocarbon chains are straight due to the C-C single bonds; they like to be close together

At room temperature, which fatty acid is usually solid, and which fatty acid is usually liquid?

-Saturated fatty acids are usually solid

-Unsaturated fatty acids are usually liquid

Which fatty acid decreases membrane fluidity and which fatty acid increases membrane fluidity?

-Saturated fatty acids decrease membrane fluidity

-Unsaturated fatty acids increase membrane fluidity -

What defining characteristics do all sterols have?

a tetracyclic core

What makes sterols amphipathic?

One end has a polar (hydrophilic) region

One end has a nonpolar (hydrophobic) region; nonpolar region is the tail of the fatty acid

True or False: fatty acids can have ester or ether linkages?

True

Where are steroids derived from?

Sterols

When comparing the structure or sterols to steroids what is a major difference between the two?

Steroids have lost the hydrophobic tail

What are isoprenoids(terpenoids) made of?

Built from repeating 5-carbon isoprene units composed of hydrocarbons

Why are Isoprenoids mostly hydrophobic?

-they consist largely of nonpolar hydrocarbons chains and rings

What would make an Isoprenoid less hydrophobic?

-If it contains a polar functional group, it will be less hydrophobic

What does the attachment of an isoprenoid tail to a protein allow?

Attachment of an isoprenoid (prenyl) tail anchors a protein to the cytosolic surface of a membrane. The isoprenoid tail inserts into the lipid bilayer, while the protein remains accessible from the cytosol and generally does not span the membrane.

What are 4 biological functioins of lipids?

-storage of energy

-insulation from environment; absorbs heat/shock

-water repellant

-buoyancy control and acoustics of marine mammals

-membrane structure

-cofactor for enzyme; vitK, coenzyme Q

-Hormones

-Antioxidants

-Pigmentation

Which lipids contain fatty acids?

storage and membrane lipids

which lipids do not contain fatty acids?

cholesterol (with esters) and isoprenes

Which type of lipid are triacylglycerols?

storage lipids

Which type of lipid are phospholipids and glycolipids?

membrane lipids

Which lipids fall under phospholipids?

glycerophospholipids and sphingolipids

Which lipids fall under glycolipids?

sphingolipids and galactolipids (glycoglycerolipids)

General structure of a triacylglycerols

-glycerol back bone + 3 fatty acids

General structure of glycerophospholipids

-glycerol back bone + 2 fatty acids + phosphate group w/ head group

General structure of sphingolipids

sphingosine back bone + 1 fatty acid + phosphate group with head group

General structure of sphingoglycolipids

sphingosine back bone + 1 fatty acid + sugar (mono or oligosaccharide)

General structure of Galactolipids (glycoglycerolipids)

glycerol back bone + 2 fatty acids + sugar (mono or disasccharide) with sulfate

In a sphingosine, where does the fatty acid attach?

attaches to the amine

What are fatty acids?

Carboxylic acids with hydrocarbon chains containing from 4 to 36carbons

Are most natural fatty acids unbranched or branched?

unbranched

What is monounsaturated and polyunsaturated?

Monounsaturated:one double bond between carbons in the alkyl chain

Polyunsaturated:more than one double bond in the alkyl chain

Which non-covalent interaction do unsaturated lipids weaken?

Van der waals

In which configuration, trans or cis, are double bonds almost always presented in?

cis

What determines the solubility of lipids in water?

chain length and saturation; longer fatty acids are poorly soluble

What two factors control whether lipids are solids or liquids at room temperature?

chain length and saturation

Does the prescence of cis double bonds increase or decrease solubility?

increases

Double bonds = kinks = less packing = weaker fatty acid-fatty acid interactions = slightly greater solubility and much greater fluidity.

Melting point blank as the chain length increase and blank with the presence of double bonds

-increases

-decreases

In type of fatty acid are the majority in biological systems found in?

triacylglycerols

Are triacylglycerols less dense or more dense than water?

less dense; fats and oils float

Fats and oils are?

triacylglycerols

why are triacylglycerols less soluble in water?

due to the lack of charge carboxylate group OR

triacylglycerols are really nonpolar; has 3 long hydrocarbon tails

How can triacylglycerols (fats/oils) release free fatty acids

-the stored fat in adipocytes contain lipase, which hydrolyzes the triacylglycerols to release free fatty acids

What are waxes made of?

Waxes are lipids made from the combination of:

• A long-chain fatty acid (saturated and unsaturated )

• A long-chain alcohol

These two molecules are joined by an ester bond.

True or false: waxes have low melting points and are soluble

False: waxes have high melting points and are insoluble

In glycerophospholipids, are the fatty acids attached to the C-1 generally saturated or unsaturated, and what is the carbon length?

generally saturated and are C16 or C18

In glycerophospholipids, are the fatty acids attached to the C-2 generally saturated or unsaturated, and what is the carbon length?

generally unsaturated and are C18 or C20

In glycerphospholipids, what variety is seen in the head groups that are attached to the phosphate?

they can make the glycerophospholipids negatively or positively charged or neutral

Which glycerophospholipids are the major components of most eukaryotic membranes?

Phosphatidylcholine and phosphatidylethanolamine

Which glycerophospholipid is the most abundant in prokaryotic cell membranes?

Phosphatidylethanolamine

Some glycerophospholipids contain fatty acids in which type of linkage?

Ether

Which ether lipid is about 50% of heart phospholipids?

Plasmalogen

Are ether-linked alkanes stable or unstable?

stable; harder to break

In sphingolipids, the polar head group is connected to sphingosine by which linkages?

-glycosidic or phosphodiester linkage

What are the roles of cholesterol and related sterols that are present in the membranes of most eukaryotic cells?

-modulate fluidity and permeability

-thicken the plasma membrane

How do mammals obtain cholesterol?

food and de novo synthesis in the liver

How is cholesterol transported?

It is bound to proteins

In which density does cholesterol tend to deposit and clog arteries?

cholesterol in LDL (low-density lipoproteins)

Are steroids or sterols more polar?

steroids due the lack of the alkyl chain

Where are steroid hormones synthesized and from what?

synthesized in gonads and adrenal glands from cholesterol

-cortisol, testosterone, aldosterone

monoterpene

C10

sesquiterpene

C15

diterpene

C20

triterpene

-C30

polyterpene

>C40

Where are isoprenoids (terpenes) derived from?

IPP and its DMAPP

what is this the general structure of?

Where are the sugar-containing glycosphingolipids largely found?

outer face of plasma membrane