Problem 3 - Campbell Biology

Question

Which of the following is true of unsaturated fats? (A) They are more common in animals than in plants. (B) They have double bonds in their fatty acid chains. (C) They generally solidify at room temperature. (D) They contain more hydrogen than do saturated fats having the same number of carbon atoms.

Step-by-Step Solution

Answer

The correct statement is (B) They have double bonds in their fatty acid chains.

Step 1: Identify Key Characteristic of Unsaturated Fats

Unsaturated fats are fatty acids that have at least one double bond within the fatty acid chain. This is the primary characteristic.

Step 2: Evaluate Option A

Option A states unsaturated fats are more common in animals than in plants. Typically, unsaturated fats are more common in plants.

Step 3: Evaluate Option B

Option B indicates that unsaturated fats have double bonds in their fatty acid chains. This is correct because the presence of double bonds is what makes a fat unsaturated.

Step 4: Evaluate Option C

Option C asserts that unsaturated fats generally solidify at room temperature. In reality, unsaturated fats are usually liquid at room temperature due to their double bonds creating kinks in the chains.

Step 5: Evaluate Option D

Option D mentions that unsaturated fats contain more hydrogen than saturated fats with the same number of carbon atoms. This is incorrect because unsaturated fats have fewer hydrogen atoms due to the presence of double bonds.

Step 6: Conclusion

Based on the evaluation of each option, it is clear that the statement about unsaturated fats having double bonds in their fatty acid chains is true.

Key Concepts

fatty acid chains

Fatty acid chains are long chains of carbon atoms bonded to hydrogen atoms. These chains form the building blocks of fats and oils.
The arrangement of carbon and hydrogen atoms in these chains determines the type of fat.
Here are some key points about fatty acid chains:

• Length: Fatty acid chains can vary in length, typically ranging from 4 to 28 carbon atoms.
• Saturation: Fatty acids can be saturated or unsaturated based on the presence of double bonds between carbon atoms.

Understanding these chains is essential since they define the properties and functions of different fats.

double bonds

Double bonds play a crucial role in differentiating types of fats.
A double bond occurs when two carbon atoms within a fatty acid chain share two pairs of electrons.
This bond changes the structure and properties of the fatty acid.

• Monounsaturated fats: These fatty acids have one double bond.
• Polyunsaturated fats: These fatty acids contain more than one double bond.
• Effect on Shape: The presence of double bonds introduces 'kinks' in the chain, preventing tight packing.

These structural differences due to double bonds account for the liquid nature of many unsaturated fats at room temperature.

unsaturated vs saturated fats

It’s essential to understand the differences between unsaturated and saturated fats. This will help in recognizing their sources, benefits, and effects on health.

• Unsaturated fats: These fats have one or more double bonds in their fatty acid chains, making them usually liquid at room temperature. They are commonly found in plants, such as olive oil and nuts.
• Saturated fats: These fats have no double bonds, resulting in tightly packed molecules that are solid at room temperature. They are typically found in animal products like butter and meat.
• Health Implications: Unsaturated fats are considered healthier for the heart, as they can help reduce bad cholesterol levels. Saturated fats, on the other hand, might increase the risk of heart disease when consumed in excess.