$$II = d \times MI2 \times 100 / M_{lip}$$

Question 1

Which of the following statements best explains why butyric acid (C4) is soluble in water, while fatty acids with more than 10 carbons are not?

Accepted Answer

Longer hydrocarbon chains increase hydrophobic interactions, reducing solubility in water.

Question 2

What is the effect of increasing the number of double bonds in a fatty acid on its melting point?

Accepted Answer

The melting point decreases as the number of double bonds increases.

Question 3

Which equation correctly represents the calculation of the iodine value (II) for a lipid sample?

Accepted Answer

$$II = d 	imes MI2 	imes 100 / M_{lip}$$

Question 4

Which chemical reaction is responsible for the rancidity of fats exposed to air?

Accepted Answer

Oxidation of double bonds by oxygen

Question 5

What is the biological significance of omega-3 fatty acids in human health?

Accepted Answer

They are important for brain and vision development and reduce the risk of coronary heart disease.

Question 6

Which process is used to convert edible oils of unsaturated fatty acids into margarine?

Accepted Answer

Hydrogenation

Question 7

What is the correct formula for the acid value ($$I_A) of a $$fatty acid sample?

Accepted Answer

$$I_A = M_{KOH} \cdot 10$$^{+3}$$ / Mag$$

Question 8

Which of the following is a property of carboxylate salts (soaps) in water?

Accepted Answer

They dissociate into hydrophilic and hydrophobic ions, lowering water surface tension.

Question 9

Which enzyme is responsible for the synthesis of oleic acid (C18:1, ω9) in both plants and animals?

Accepted Answer

Δ9 desaturase

Question 10

Why are linoleic acid (C18:2, ω6) and alpha-linolenic acid (C18:3, ω3) considered essential fatty acids?

Accepted Answer

Humans cannot synthesize them due to lack of certain desaturase enzymes.

Question 11

Which of the following best describes the organization of insoluble fatty acids at the water-air interface?

Accepted Answer

They form molecular films (mono-, bi-, or multilayer) or micelles.

Question 12

What is the main energy-related advantage of triglycerides compared to carbohydrates?

Accepted Answer

Triglycerides produce twice as much energy per gram as carbohydrates.

Question 13

Which reaction describes the saponification of a fatty acid with potassium hydroxide (KOH)?

Accepted Answer

$$R-COOH + KOH \rightarrow RCOO^- K^+ + H_2O$$

Question 14

Which of the following is NOT a functional role of linoleic acid in humans?

Accepted Answer

It acts as a major energy source during fasting.

Question 15

What is the result of the addition reaction between a fatty acid double bond and iodine (I2)?

Accepted Answer

Iodine binds to the double bond, allowing quantification of unsaturation.

Question 16

Which of the following best describes the difference between homogeneous and heterogeneous triglycerides?

Accepted Answer

Homogeneous triglycerides have three identical fatty acids; heterogeneous have different fatty acids.

Question 17

Which chemical property of fatty acids is exploited in the industrial production of margarine?

Accepted Answer

Hydrogenation of double bonds to produce saturated fatty acids

Question 18

Which of the following reactions represents the formation of an ester from a fatty acid and an alcohol?

Accepted Answer

$$R-COOH + R'-OH \rightarrow R-CO-O-R' + H_2O$$

Lipids: Structure, Properties, and Biological Roles

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