BCH 369 EXAM 2 CH8 pt3

why are tricycglycerols higher in energy storage form

Because of the highly reduced nature of their nonpolar tails

What happens to surface area and thickness?

Surface are increases, thickness decreases

Phosphatidic acid structure

2 fatty acids and phosphoric acid esterified to 3-OH groups of glycerol

What structural features do a sphingomyelin and a phosphatidyl choline have in common? How do the structures of these two types of lipids differ?

Both sphingomyelins and phosphatidylcholines contain phosphoric acid esterified to an amino alcohol, which must be choline in the case of a phosphatidylcholine and may be choline in the case of a sphingomyelin. They differ in the second alcohol to which phosphoric acid is esterified. In phosphatidylcholines, the second alcohol is glycerol, which has also formed ester bonds to two carboxylic acids. In sphingomyelins, the second alcohol is another amino alcohol, sphingosine, which has formed an amide bond to a fatty acid.

what are the fused-ring compounds

Cholesterol Steroid hormones Bile acids

what are the open-chain compounds

Fatty acids Triacylglycerol Sphingolipids Phosphoacylglyverols Glycoplipids

glycolipid structure

Glycerol, 2 Fatty Acids, and a Carb. Amphipathic.

intermolecular forces holding lipids together

Held together by van der waals & hydrophobic interactions

What is the energetic driving force for the formation of phospholipid bilayers?

Hydrophobic interactions among the hydrocarbon tails are the main energetic driving force in the formation of lipid bilayers.

What structural features do a triacylglycerol and a phosphatidyl ethanolamine have in common? How do the structures of these two types of lipids differ?

In both types of lipids, glycerol is esterified to carboxylic acids, with three such ester linkages formed in triacylglycerols and two in phosphatidyl ethanolamines. The structural difference comes in the nature of the third ester linkage to glycerol. In phosphatidyl ethanolamines, the third hydroxyl group of glycerol is esterified not to a carboxylic acid but to phosphoric acid. The phosphoric acid moiety is esterified in turn to ethanolamine.

why is the bilayer considered asymmetric with regard to lipid type and what is the effect of this

Inner and outer layers contain mixtures of lipids · Bulkier molecules in outer layer Smaller molecules in inner layer

Which is more hydrophilic, cholesterol or phospholipids?

Phospholipids are more hydrophilic than cholesterol. The phosphate group is charged, and the attached alcohol is charged or polar. These groups interact readily with water. Cholesterol has only a single polar group, an .

Proteins, nucleic acids, and carbohydrates are grouped by common structural features found within their group. What is the basis for grouping substances as lipids?

Solubility properties (insoluble in aqueous or polar solvents, soluble in nonpolar solvents). Some lipids are not at all structurally related.

What structural features does a sphingolipid have in common with proteins? Are there functional similarities?

Sphingolipids contain amide bonds, as do proteins. Both can have hydrophobic and hydrophilic parts, and both can occur in cell membranes, but their functions are different.

what is the effect of cholesterol on membrane fluidity

Stabilizes the straight chain arrangement of saturated fatty acid tails which increases the effect of the van der waals interaction and leads to a more rigid membrane structure

How does the structure of steroids differ from that of the other lipids discussed in this chapter?

Steroids contain a characteristic fused-ring structure, which other lipids do not.

what is saponification

The cleavage of triacyglycerols via NaOH.

Suggest a reason why animals that live in cold climates tend to have higher proportions of polyunsaturated fatty acid residues in their lipids than do animals that live in warm climates.

The higher percentage of unsaturated fatty acids in membranes in cold climates is an aid to membrane fluidity.

In the preparation of sauces that involve mixing water and melted butter, egg yolks are added to prevent separation. How do the egg yolks prevent separation? Hint: Egg yolks are rich in phosphatidylcholine (lecithin).

The lecithin in the egg yolks serves as an emulsifying agent by forming closed vesicles. The lipids in the butter (frequently triacylglycerols) are retained in the vesicles and do not form a separate phase.

In the produce department of supermarkets, vegetables and fruits (cucumbers are an example) have been coated with wax for shipping and storage. Suggest a reason why this is done.

The surface wax keeps produce fresh by preventing loss of water.

In lipid bilayers, there is an order-disorder transition similar to the melting of a crystal. In a lipid bilayer in which most of the fatty acids are unsaturated, would you expect this transition to occur at a higher temperature, a lower temperature, or the same temperature as it would in a lipid bilayer in which most of the fatty acids are saturated? Why?

The transition temperature is lower in a lipid bilayer with mostly unsaturated fatty acids compared with one with a high percentage of saturated fatty acids. The bilayer with the unsaturated fatty acids is already more disordered than the one with a high percentage of saturated fatty acids.

Succulent plants from arid regions generally have waxy surface coatings. Suggest why such a coating is valuable for the survival of the plant.

The waxy surface coating is a barrier that prevents loss of water.

You have just isolated a pure lipid that contains only sphingosine and a fatty acid. To what class of lipids does it belong?

This lipid is a ceramide, which is one kind of sphingolipid.

Which of the following lipids are not found in animal membranes?

Triacylglycerols are not found in animal membranes.

What are the structural features of waxes? What are some common uses of compounds of this type?

Waxes are esters of long-chain carboxylic acids and long-chain alcohols. They tend to be found as protective coatings.

difference between cerebroside and gangliosides

cerebroside- Glyosidic bond formed between 1' alcohol of ceramide and sugar residue (glucose or galactose) gangliosides- Glycolipids with complex carbohydrate moiety that contains >3 sugars · One is always sialic acid

Tor F: Cis double bonds in unsaturated fatty acids are conjugated

false

where are triacyglycerols found

in adipose tissue

what is the affect of chain length on melting point & interactions

melting point and van der waals interactions increases with chain length

two states of the membrane

o Ordered and rigid o Disordered and fluid

what is the storage form of fat

triacylglycerol

T or F: plants have more fluid membranes than animals

true

Know the sphingosine backbone

§ Contains 2 fatty acids chains based on the sphingosine backbone § Second fatty acid chain linked to sphingosine via amide bond

general structure of lipid vesicles

§ Inner aqueous compartment § Inner layer is more tightly packed

Phosphatidyl Esters structure

· One molecule can form ester bonds to glycerol and to some other alcohol to create phophatidyl esters