Question

Which of the following statements are true?

 1. Fats that contain more saturated fatty acid residues than unsaturated fatty acid residues are more likely to be solid at room temperature.

 2. Triacylglycerols (triglycerides) contain ester bonds.

 3. Saturated fats have lower melting points than do unsaturated fats.

 4. Triacylglycerols (triglycerides) always contain three identical fatty acids.

 5. Unsaturated fats are more likely than saturated fats to be liquid at room temperature.

Answer 1

Concepts and reason

Triglycerides are lipids consisting of one glycerol molecule which bonds with three fatty acid molecules through a condensation reaction. The bonds formed are called ester bonds and are covalent. Fats and oils are triglycerides.

Fundamentals

The residues of fatty acid in the triglyceride may be saturated or unsaturated. The amount of saturated or unsaturated fatty acid residues in the triglyceride determines the properties of triglycerides like melting point, boiling point, its state at room temperature.

Part 1

The hydrocarbon tails of fatty acids(saturated) are able to pack together as they interact through London forces. This increases the melting point of the saturated fatty acids. Hence, the fats containing more saturated fatty acid residues are more likely to be solid at room temperature.

This is a true statement.

Part 2

Triglyceride contains one glycerol molecule bonded with three fatty acid molecules. The carboxyl group of fatty acid combines with the hydroxyl group of glycerol, forming an ester bond. The ester bonds are covalent.

Therefore, triglycerides contain ester bonds.

Thus, the above statement is true.

Part 3

The hydrocarbon tails of fatty acids are able to pack together as they interact through London forces. This increases the melting point of the saturated fats. Therefore, saturated fats have higher melting points than do unsaturated fats.

Thus, the given statement is false.

Part 4

Triglyceride contains one glycerol molecule bonded with three fatty acid molecules. The triglycerides may contain three identical fatty acids or they may be derived from two or three different fatty acids.

Thus, the given statement is false.

Part 5

The unsaturated fatty acid residues in unsaturated fats do not allow molecules to pack together very well due to cis configuration in hydrocarbon tails. So, the more unsaturated fatty acid residues a triglyceride (fat) have, the lower its melting point.

Therefore, unsaturated fats are more likely to be liquid at room temperature.

Hence, the given statement is true.

Ans: Part 1

Fats that contain more saturated fatty acid residues than unsaturated fatty acid residues are more likely to be solid at room temperature is True.

Part 2

Triacyclglycerols (triglycerides) contain ester bonds is True.

Part 3

Saturated fats have lower melting points than do unsaturated fats is False.

Part 4

Triglycerides always contain three identical fatty acids is False.

Part 5

Unsaturated fats are more likely than saturated fats to be liquid at room temperature is True.