chapter 11

some important omega-3 fatty acids:

- alpha-linolenate - EPA and DHA - found in fatty fish and shellfish

some characteristics of steroids:

- function as powerful hormones - facilitate the digestion of lipids in the diet - key membrane constituents

the platform on which phospholipids are built may be:

- glycerol (a three carbon alcohol) - sphingosine (an amino alcohol)

membrane lipids are primarily comprised of:

- phospholipids - glycolipids

the same number of carbon atoms, what is the melting point of saturated, trans, and cis all compared?

- saturated has the highest melting point - trans has the next highest melting point - cis has the lowest melting point

common alcohol moieties of phosphoglycerides:

- serine - ethanolamine - choline - glycerol - inositol

characteristics of membrane lipids:

- they are amphipathic molecules - they contain both a hydrophilic and hydrophobic moiety

some characteristics of triacylglycerols:

- they are hydrophobic (do not bind to water molecules) - they are stored in a nearly anhydrous form

some biochemical roles that lipids play:

- widely used to store energy - key components of membranes - involved in signal-transduction pathways

1 gram of nearly anhydrous fat v. 1 gram of hydrated glycogen:

1 gram of nearly anhydrous fat stores more than 6x as much energy as 1 gram of hydrated glycogen

phospholipids are composed of four components:

1) fatty acids (one or more) 2) platform (to which the fatty acids are attached) - glycerol 3) phosphate 4) alcohol (attached to the phosphate)

the 5 classes of lipids:

1) free fatty acids 2) triacylglycerols 3) phospholipids 4) glycolipids 5) steroids

two key roles for fatty acids:

1) fuels 2) building blocks for membrane lipids

three common types of membrane lipids:

1) phospholipids 2) glycolipids 3) steroids (cholesterol)

children affected by HGPS usually die at the age of:

13 years from severe atherosclerosis

the number of carbons in most common fatty acid is:

16 or 18

number of carbon fatty acids that is the most common:

16- and 18-carbon fatty acids

cholesterol constitutes almost...

25% of the membrane lipids in certain nerve cells, but is essentially absent from some intracellular membranes

octadecatrienoic acid has how many double bonds?

3

the polar head group of phospholipids is found at which carbon of glycerol?

C3

a hydrophobic group that is often attached to proteins, usually so the protein is able to associate with a membrane:

Farnesyl

inappropriate farnesylation has been shown to result in:

Hutchinson-Gilford progeria syndrome (HGPS) - a rare disease of premature aging

do lipids form polymers?

NO - unlike carbohydrates, amino acids, and nucleic acids, they do not

what is necessary for a protein to associate with a hydrophobic environment, such as a membrane?

a lipid must be attached to the protein

adipose tissue also serves as:

a thermal insulator to help maintain body temperature

the major site of accumulation of triacylglycerols in mammals:

adipose tissue (it's distributed under the skin and elsewhere throughout the body)

a term applied to molecules that have both hydrophilic and hydrophobic properties:

amphipathic

sphingosine:

an amino alcohol that contains a long, unsaturated hydrocarbon chain

fatty acids in biological systems usually contain _____ number of carbon atoms:

an even number - usually between 14 and 24

glycolipids are oriented in an...

asymmetric fashion in membranes with the sugar residue always on the extracellular side of the membrane

why do fats yield more energy than carbohydrates when undergoing combustion to carbon dioxide and water?

because fats are more reduced than carbohydrates - the carbon atoms are bonded to hydrogen atoms and other carbon atoms rather than to oxygen atoms, as is the case for carbohydrates

why is the concentration of free fatty acids in cells or the blood low?

because free fatty acids are strong acids - high concentrations of free fatty acids would disrupt the pH balance of the cells

natural soaps are prepared by:

boiling triacylglycerols with NaOH

how are triacylglycerols formed?

by the attachment of 3 fatty acid chains to a glycerol molecule through ester linkages (through a process known as esterification)

fatty acids are richer in energy than:

carbohydrates (they are hydrophilic - bind to water molecules)

fatty acids are ionized at physiological pH and so are referred to in their _____ form:

carboxylate

fatty acids terminate with a:

carboxylic acid group

the simplest glycolipid:

cerebroside - contains a single sugar residue, either glucose or galactose

a flat polycyclic molecule that is absent in prokaryotic membranes:

cholesterol

in addition to phospholipids and glycolipids, _______ is a major type of membrane lipid:

cholesterol

the most common steroid is:

cholesterol

the most common steroid:

cholesterol - it is the precursor to many biochemically active steroids

the configuration of the double bonds in most unsaturated fatty acids:

cis

the shorthand notation indicating that there are two cis double bonds between carbons 9 and 10, and again be tween 12 and 13:

cis, cis(delta)9,12

what are essential in our diets?

cis-polyunsaturated fatty acids (like omega-3 fatty acids) - they help protect against cardiovascular disease

in adipose cells, drops of triacylglycerols...

coalesce to form a large globule in the cytoplasm, which may occupy most of the cell volume

steroids function as hormones that...

control a variety of physiological functions

a type of lipid that is less resistant to hydrolysis, potentially because of the way the acyl chain is linked to the glycerol backbone:

ether-linked lipid

chains of hydrogen-bearing carbon atoms (called hydrocarbons) which terminate with carboxylic acid groups:

fats, or fatty acids

when energy is required for a fast, what happens?

fatty acids are cleaved from the triacylglycerol and carried to the cells

the simplest type of lipid that is most commonly used as a fuel:

free fatty acids

a more complex glycolipid:

ganglioside - contain a branched chain of as many as seven sugar residues

the backbone of a phospholipid:

glycerol

lipids which contain carbohydrates is/are:

glycolipid

lipids that are bound to carbohydrates and are important membrane constituents:

glycolipids

sugar-containing lipids:

glycolipids

the longer the fatty acid, the _______ the fatty acid:

higher the melting point of

structure of phosphatidate:

hydroxyl groups at C-1 and C-2 of glycerol are esterified to the carboxyl groups of the two fatty acid chains, and the C-3 hydroxyl group of the glycerol backbone is esterified to phosphoric acid

the melting point of polyunsaturated fatty acids...

is even lower than unsaturated fatty acids

the properties of fatty acids depend on:

length and degree of unsaturation

water-insoluble molecules that are highly soluble in organic solvents:

lipids

the reduction in tight packaging due to cis double bonds ______ the melting temperature of a fatty acid:

lowers

the double bonds in polyunsaturated fatty acids are separated by at least one:

methylene group

a lipid is defined as a compound soluble in:

organic solvent

polar head groups of phospholipids are esterified to which functional group?

phosphate

the simplest phosphoglyceride:

phosphatidate (diacylglycerol 3-phosphate)

membrane lipids with a glycerol backbone:

phosphoglyceride

phospholipids derived from glycerol:

phosphoglycerides - they are composed of a glycerol backbone to which are attached two fatty acid chains and a phosphorylated alcohol

a type of lipid with two acyl chains, a glycerol backbone, and a polar head group:

phospholipid

membrane lipids that consist of fatty acids that create a macromolecule with a polar head and non polar tail:

phospholipids

the major class of membrane lipids:

phospholipids

cholesterol is absent from:

prokaryotes

cholesterol is important in maintaining:

proper membrane fluidity (it increases membrane fluidity by preventing tight packing)

what are correlated with high blood levels and cardiovascular disease?

saturated and trans-unsaturated fats in the diet

fatty acids composed of single bonds only:

saturated fatty acids - every carbon atom is attached to four other atoms

soaps are the:

sodium or potassium salts of long chain fatty acids

phospholipids built on a sphingosine backbone:

sphingolipids

a common sphingolipid found in membranes:

sphingomyelin - especially rich in the myelin sheath of nerve cells

a complex amino alcohol backbone for membrane lipids:

sphingosine

glycolipids are derived from:

sphingosine

lipids that are polycyclic hydrocarbons:

steroids

all steroids have a:

tetracyclic ring structure called the steroid nucleus

the utility of triacylglycerols as an energy source is dramatically illustrated by:

the abilities of migratory birds

short chain and cis unsaturation enhance...

the fluidity of fatty acids and of their derivatives

the major phosphoglycerides are derived from phosphatidate by:

the formation of an ester linkage between the phosphoric group of phosphatidate and the hydroxyl group of one of several alcohols

triacylglycerol stores are replenished by:

the ingestion of food

longer chains offer more point of contact for van der Waals interactions and increase:

the melting points

adipose cells are specialized for:

the synthesis and storage of triacylglycerols and for their mobilization into fuel molecules that are transported to other tissues by the blood

soaps are derived from:

the treatment of triacylglycerols with a strong base (this process is known as saponification)

characteristics of glycolipids:

they are ubiquitous in all cell membranes where they play a role in cell-cell interactions

why do cis fatty acids have lower melting temperature?

they lack tight packing which limits the van der Waals interactions between chains and results in a lower melting temperature

the steroid nucleus consists of:

three cyclohexane (6 sides) rings and a cyclopentane (5 sides) ring joined together

lipid that is the storage form of fatty acids:

traicylglycerols

which fatty acid has higher symmetry - trans or cis?

trans fatty acids have higher symmetry and can pack better - they have higher melting points

the storage form of fatty acids:

triacylglycerol

fatty acids required for energy generation are stored as:

triacylglycerols (TAG)

structure of steroids:

unlike the other classes of lipids, they take on a cyclical rather than linear structure

fatty acids with one or more double or triple bonds are called:

unsaturated fatty acids

melting point of saturated v. unsaturated fatty acids:

unsaturated fatty acids have lower melting points than those of saturated fatty acids of the same length

the presence of double bonds in fatty acids limits tight packaging and the number of _____ interactions:

van der Waals