Question 1

Which structural feature distinguishes naturally occurring unsaturated fatty acids from saturated fatty acids, and how does this affect their physical properties?

Accepted Answer

Unsaturated fatty acids contain cis double bonds, which introduce kinks in the hydrocarbon chain, lowering their melting point and making them liquid at room temperature.

Question 2

Which of the following best describes the structure of a wax, as seen in beeswax and carnauba wax?

Accepted Answer

A monoester formed from a long-chain fatty acid and a long-chain alcohol.

Question 3

Which equation correctly represents the general structure of a triacylglycerol (fat or oil)?

Accepted Answer

$$\mathrm{CH_2OCO\,R^1$\,\,\,CH\,OCO\,R^2$\,\,\,CH_2OCO\,R^3$}$$

Question 4

Why are phospholipid bilayers not 'leaky' compared to micelles formed by soaps?

Accepted Answer

Phospholipids have two hydrophobic tails that pack tightly together, preventing gaps and leakage.

Question 5

Which of the following is an essential fatty acid that humans must obtain from their diet?

Accepted Answer

Linoleic acid (18:2, omega-6)

Question 6

What is the role of cholesterol in the cell membrane, as depicted in the phospholipid bilayer diagram?

Accepted Answer

Cholesterol modulates membrane fluidity and stability by fitting between phospholipid tails.

Question 7

Which of the following statements about terpenes is correct?

Accepted Answer

Terpenes are constructed from multiples of five-carbon isoprene units, which are linked according to specific rules.

Question 8

Which of the following best explains why highly unsaturated oils (like canola oil) are liquid at room temperature?

Accepted Answer

The presence of multiple cis double bonds prevents tight packing of the hydrocarbon chains, lowering the melting point.

Question 9

Which of the following is NOT a function of waxes in nature?

Accepted Answer

Serving as a major energy storage molecule in animals.

Question 10

Which of the following correctly describes the relationship between lanosterol and cholesterol?

Accepted Answer

Lanosterol is a precursor to cholesterol, formed by cyclization and rearrangement of squalene.

Question 11

Which of the following best describes the structure of a phospholipid found in cell membranes?

Accepted Answer

A glycerol backbone esterified to two fatty acids and one phosphoric acid, with a second alcohol attached to the phosphate.

Question 12

Which equation represents the general structure of a fatty acid?

Accepted Answer

$$\mathrm{RCOOH}$$

Question 13

Which of the following is a correct classification for a terpene with 20 carbon atoms?

Accepted Answer

Diterpene

Question 14

Which of the following hormones is derived from cholesterol?

Accepted Answer

Cortisol

Question 15

Which of the following best explains the semi-fluid property of cell membranes?

Accepted Answer

Phospholipids contain both saturated and unsaturated fatty acids, allowing for flexibility and fluidity.

Question 16

Which of the following is a correct description of the isoprene rule for terpenes?

Accepted Answer

Terpenes are constructed from C5 units linked head-to-tail, with classification based on the number of C10 units.

Question 17

Which of the following is a real-world application of phospholipids?

Accepted Answer

They form the structural basis of cell membranes, creating a bilayer that separates cell contents from the environment.

Question 18

Which of the following best explains why cell membranes do not allow cell contents to escape?

Accepted Answer

The tight packing of phospholipid tails in the bilayer prevents leakage.

Question 19

Which of the following is a correct description of the function of steroids in biological systems?

Accepted Answer

Steroids act as hormones regulating various physiological processes, such as blood pressure and reproductive functions.

Chapter 20: The Organic Chemistry of Lipids

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