Chapter 11: Lipids

Question 1

Define: Fatty Acid

Answer 1

Chains of hydrogen-bearing carbon atoms.

Question 2

Define: Triacyglycerol

Answer 2

Storage form of fatty acids

Question 3

Define: Phospholipid

Answer 3

Major class of membrane lipids

Question 4

Define: Sphinogosine

Answer 4

A complex alcohol backbone for membrane lipids

Question 5

Define: Phosphoglyceride

Answer 5

Membrane lipids with a glycerol backbone

Question 6

Define: Sphingomyelin

Answer 6

Phospholipid especially common in nerve cells.

Question 7

Define: Glycolipid

Answer 7

Derived from sphingosine and found in all membranes

Question 8

Define: Cerebroside

Answer 8

The simplest Glycolipid

Question 9

Define: Cholesterol

Answer 9

Steroid-based lipid

Question 10

Triacyglycerols are used for fuel storage in both plants and animals. The Triacyglycerols from plants are often liquid at room temperature, where as those from animals are solid. Suggest some chemical reasons for this difference.

Answer 10

Triacyglycerols from plants may have many cis double bonds or have shorter fatty acid chains than those from animals.

Question 11

Distinguish between Phosphoglycerides and Triacyglycerols.

Answer 11

Triacyglycerols consist of three fatty acid chains attached to a glycerol backbone. Triacyglycerols are a storage form of fuel.

Phosphoglycerides consist of two fatty acid chains attached to a glycerol backbone. The remaining alcohol of the glycerol is bonded to a phosphate, which is in turn bonded to an alcohol. Phosphoglycerides are membrane components.

Question 12

What structural characteristic of lipids accounts for their solubility in organic solvents?

Answer 12

Lipids are primarily hydrophobic molecules. This primarily hydrophobic nature accounts for their solubility in organic solvents and their lack of solubility in aqueous solvents.

Question 13

What are lipids?

Answer 13

Lipids are organic water-insoluble molecules that are highly soluble in organic solvents.

Question 14

Membranes lipids are primarily comprised of:

Answer 14

Phospholipids and glycolipids.

Question 15

Octadecatrienoic acid has how many double bonds?

Answer 15

3

Question 16

The notation 12:2 indicates which of the following about a fatty acid?

Answer 16

There are 12 carbons in the chain with 2 double bonds.

Question 17

The longer the fatty acids, the _______ the fatty acid.

Answer 17

The higher the melting point of

Question 18

Unsaturations ______ melting points of fatty acids and their derivatives.

Answer 18

Decrease

Question 19

The backbone of a phospholipid is which of the following?

Answer 19

Glycerol

Question 20

Polar head groups of phospholipids are esterified to what functional group?

Answer 20

Phosphate

Question 21

A phosphatidate lipid (phosphatidic acid) has which of the following components?

Answer 21

1. Ester linkage
2. Acyl Chain
3. Phosphate
4. Glycerol

Question 22

Which of the following best describes the cholesterol molecule?

Answer 22

Amphipathic

Question 23

Why are tricylglycerols used in the human body for energy storage?

Answer 23

The carbon atoms of the fatty acid chains are highly reduced and therefore yield more energy upon oxidation.

Question 24

Suppose that a small amount of phospholipid were exposed to an aqueous solution. What structure would the phospholipid molecules assume? What would be the driving force for the formation of the structure?

Answer 24

The hydrophobic chains would shun the water, interacting with similar chains in other molecules. Meanwhile, the hydrophilic head groups would readily interact with the water, resulting in the formation of a membrane or a small membrane vesicle called a liposome.

Question 25

Why are lipids a more efficient storage form than glycogen?

Answer 25

Lipids are more reduced than glycogen, and they are stored in an anhydrous form.

Question 26

Small mammalian hibernators can withstand body temperatures of 0 degrees to 5 degrees Celsius without injury. However, the body fats of most mammals have melting temperatures of approximately 25 degrees Celsius.

Predict how the composition of the body fat of hibernators might differ from that of their non-hibernating cousins.

Answer 26

Hibernators selectively feed on plants that have a high proportion of polyunsaturated fatty acids with lower melting temperature.