MBIO 2730 LIPIDS & MEMBRANES

Functions of lipids

energy storage; membrane components; coenzymes; electron carriers; light absorbing pigments; intracellular messengers; detergents

Are lipids hydrophobic or philic?

hydrophobic

Are lipids insoluble in water?

all are insoluble in water but soluble in organic solvents

What are fatty acids?

carboxylic acids with 4-36 carbons

Are fatty acids 100% hydrophobic?

they have hydrophobic and hydrophilic segments

What is an amphipathic molecule?

a molecule with both hydrophobic and hydrophilic regions

What is another name for stearic acid?

octadecanoic acid

What is the carbon to double bond ratio of stearic acid?

18:0

If stearic acid has 18 C and 0 double bonds is it saturated or unsaturated?

saturated fatty acid

What percent of body fat does stearic acid make up?

5%

At what temperature does stearic acid melt? What type of solid is it?

70 °C; a waxy solid

What is the carbon to db ratio of palmitic acid?

16:0

What percent of body fat is made up by palmitic acid?

25% of human body fat

What is the official name of oleic acid?

cis-9-octadecenoic acid

What is the carbon to db ratio of oleic acid?

18:1 (Δ9)

What is the site of unsaturation in oleic acid?

C9; known from the delta notation

What does a double bond in a fatty acid do to the tail?

a double bond puts a bend in the hydrocarbon tail

At what temperature does oleic acid melt? Why?

13 °C; low melting oil because the chains do not pack well together

What percent of human body fat is made up by oleic acid?

46%

What is the carbon to db ratio of linoleic acid?

18:2 (Δ9,12)

What is the melting point of linoleic acid?

-5 °C

Linoleic acid is an _ FA in the diets of mammals.

essential

Why is linoleic acid called an omega-6 FA?

because the last double bond is at C12 which is 6 carbons from the end of the chain; omega is the last letter in the Greek alphabet

What is the carbon to db ratio of linolenic acid?

18:3 (Δ9,12, 15)

What is the melting point of linolenic acid?

-17 °C

What is the omega number of linolenic acid?

omega-3 polyunsaturated FA

All fatty acids have an even number of what element? Is there an exception?

carbon; marine organisms may have an odd number of carbons

Do any fatty acids have conjugated double bonds?

none have conjugated double bonds

What configuration are double bonds always in in FA?

cis configuration

What types of FA are least soluble in water?

long-chain saturated fatty acids are the least soluble in water

How are fatty acids made soluble in serum?

fatty acids are made soluble in serum by binding to a protein such as albumin

What is the carboxyl pKa of FA?

4.5–5.0

What increases melting point of FA?

melting point increases with chain length

What do amphipathic FA form in water?

amphipathic fatty acids form micelles in water; water entropy drives hydrocarbon chains to associate; polar head groups interact with water; lipids can also form a monolayer at the air–water interface

What is the CMC?

critical micelle concentration; concentration of fatty acid that must be added to solution to give optimal micelle formation

What are triacyl glycerols?

neutral fats; triglycerides

What are the functions of triglycerides?

energy storage (fat cells/adipocytes; seeds); insulation; echolocation or buoyancy in sperm whales; water repellent

How much more energy does fat store than carbohydrate?

since the carbon is more reduced

What is saponifaction?

adding soap; base-catalyzed hydrolysis of triacylglycerols

The micelles formed in water can carry ______ in their interiors and still be soluble in water.

oil

What do intestinal lipases do in cells?

intestinal lipases catalyze enzymatic hydrolysis of triacylglycerols

What is the formal name for Bee's wax?

triacontanylpalmitate

What are glycerophospholipids the main component of?

cell membranes

What is phosphatidic acid?

diacylglycerol phosphate

In phosphatidic acid is R1 saturated or unsaturated?

R1 is saturated

In phosphatidic acid is R2 typically saturated or unsaturated?

R2 is unsaturated

What is the number of carbon in phosphatidic acid generally?

16 or 18

In membrane lipids one of the O on the phosphate of phosphatidic acid is bound to what to make it a glycerophospholipid?

a head group

Phosphatidylethanolamine

amino group attached to ethanol on a glycerophospholipid

Phosphatidylserine

serine head group on a glycerophospholipid

Phosphatidylcholine

choline head group on a glycerophospholipid

Why do glycerophospholipids form bilayers?

due to the hydrophobic effect and water entropy

Bilayers form spontaneously when enough glycerophospholipid is added to __ solution.

aqueous

What can curved bilayers form?

vesicles

What do phospholipases do? Where are they located?

phospholipases degrade phospholipids; they are located in lysosomes

What is a lysophospholipid?

a phospholipid from which one of the fatty acid chains has been removed

What does phospholipase A2 release?

arachidonic acid

What is arachidonic acid a precursor for?

prostaglandins; thromboxanes; leukotrienes (eicosanoids)

What are eicosanoids involved in?

inflammation; fever; pain; reproduction

What is an ether-linked fatty acid?

fatty acid linked via a carbon–oxygen–carbon ether bond

What is an example of an ether-linked FA?

plasmalogen

What type of phospholipid is platelet-activating factor?

ether-linked phospholipid hormone

What is platelet-activating factor a major cause of?

toxic shock syndrome

Are sphingolipids glycerol derivatives?

no; they are derivatives of sphingosine

What is sphingosine derived from?

the amino acid serine

What is a ceramide?

sphingosine plus a fatty acid added by an amide linkage

What is sphingomyelin?

a sphingolipid with a phosphocholine head group

What is the size and shape of sphingomyelins similar to?

glycerophospholipids

Where are sphingomyelins found?

in the plasma membrane and in the myelin sheath of axons

What allows diversity of sphingolipids?

variation in the head group and the fatty acid at the second position

What are gangliosides?

glycosphingolipids that have complex oligosaccharides as head groups

What does abnormal metabolism of ganglioside result in?

genetic diseases that often lead to mental retardation

What are some examples of diseases that may result from abnormal metabolism of gangliosides?

Tay-Sachs; Fabry; Sandhoff; Gaucher; Niemann-Pick

What are O A and B blood group antigens?

O, A, B blood group antigens are glycosphingolipids with different complex carbohydrate head groups

What are blood group antigens important for?

cell surface recognition events

What is the universal donor?

O type blood

What is the universal acceptor?

AB type blood

All blood group antigens have the same "basic tree" but different?

carbohydrate head groups

What are non-saponifiable lipids?

terpenes and steroids

What do sterols contain?

a four-fused-ring steroid nucleus

What is the most abundant sterol in human membranes?

cholesterol

What are hormonal examples of sterols?

testosterone; estradiol; progesterone; cortisol; aldosterone

What happens when sterols bind to receptors?

they bind to receptors and change gene expression

What are sterols and terpenes synthesized from?

Δ3-isopentenyl pyrophosphate (activated isoprene)

What does head to tail condensation of terpenes yield?

monoterpene geranyl pyrophosphate

What do two units form? terpene

2 units form a monoterpene (10 carbons)

What do three units form? (terpene)

3 units form a sesquiterpene (15 carbons)

What do four units form? (terpene)

4 units form a diterpene (20 carbons)

What do 6 units form? (terpene)

6 units form a triterpene (30 carbons)

What do 8 units form? (terpene)

8 units form a tetraterpene (40 carbons)

What type of pigment is beta-carotene?

beta-carotene is a tetraterpene pigment

How can animals cleave beta-carotene?

animals can cleave beta-carotene in the centre to produce 2 retinols (vitamin A1) needed for vision

What is the name for vitamin D3?

cholecalciferol

Where is vitamin D3 formed?

in skin by a UV-light photochemical reaction on 7-dehydrocholesterol

What metabolism is vitamin D important for?

Ca2+ and PO43− metabolism

What is the other name for vitamin E?

tocopherol

What level of terpene is vitamin E?

sesquiterpene

Why is vitamin E called an antioxidant?

redox reactions on its aromatic rings prevent oxidative damage to lipids

What is coenzyme Q also called?

ubiquinone

What is the role of ubiquinone?

mitochondrial electron carrier