Question

Unlike saturated fatty acids, unsaturated fatty acids a. are solid at room temperature. b. pack more tightly because they have straight chains. c. have one or more double bonds in their hydrocarbon chain. d. have the full complement (maximum number) of hydrogen atoms covalently bonded to each carbon atom in the hydrocarbon chain.

Short answer

Option C: Unsaturated fatty acids have one or more double bonds in their hydrocarbon chain.

Step-by-step solution

Understand the Question

Identify the key differences between saturated and unsaturated fatty acids. The characteristics of unsaturated fatty acids must be determined.

Option A Analysis

Unlike saturated fatty acids, unsaturated fatty acids tend to be in liquid form at room temperature, not solid. Hence, Option A is incorrect.

Option B Analysis

Unsaturated fatty acids do not pack more tightly because the presence of double bonds causes kinks in their chains, leading to looser packing. Thus, Option B is incorrect.

Option C Analysis

Unsaturated fatty acids have one or more double bonds in their hydrocarbon chain. This is a defining feature of unsaturated fatty acids. Thus, Option C is correct.

Option D Analysis

Unsaturated fatty acids do not have the maximum number of hydrogen atoms because the presence of double bonds means some carbons are not fully saturated with hydrogen. Therefore, Option D is incorrect.

Key concepts

saturated fatty acids

Saturated fatty acids are a type of fat commonly found in animal products like meat and dairy.
These fats are known for being solid at room temperature, such as butter or lard. The reason they are called 'saturated' is that they have the maximum number of hydrogen atoms attached to each carbon atom.

This means there are no double bonds between the carbon atoms in their hydrocarbon chain. Each carbon is 'saturated' with hydrogen atoms.

Saturated fatty acids pack tightly together because their hydrocarbon chains are straight. This tight packing can contribute to higher melting points, making them solid at room temperature.

Studies often link high intake of saturated fatty acids with increased risk of heart disease and other health issues. This is why it's generally recommended to consume them in moderation.

double bonds

Understanding double bonds is crucial when studying fatty acids. In chemistry, a double bond occurs when two atoms share two pairs of electrons.

For unsaturated fatty acids, these double bonds occur between carbon atoms in the hydrocarbon chain. Unlike single bonds, which allow free rotation, double bonds introduce a kink in the chain. This kink prevents unsaturated fatty acids from packing tightly, which is why these fats are usually liquid at room temperature, like oils.

There are two main types of unsaturated fatty acids based on the number of double bonds:

• Monounsaturated fatty acids (MUFAs): These have only one double bond in their hydrocarbon chain. Olive oil is a common source.
• Polyunsaturated fatty acids (PUFAs): These have more than one double bond. Examples include fish oil and sunflower oil.

A healthy diet includes a balance of these fats, as they play a role in cell membrane structure and provide essential fatty acids our body can't produce.

hydrocarbon chain

The hydrocarbon chain is an essential part of fatty acids and consists of a long chain of carbon (C) and hydrogen (H) atoms. This chain can be either saturated or unsaturated.

In saturated fatty acids, the hydrocarbon chain has single bonds between carbon atoms and is fully 'saturated' with hydrogen atoms. This gives them a straight structure, allowing them to pack tightly and be solid at room temperature.

In contrast, unsaturated fatty acids have one or more double bonds, resulting in bends or kinks in the hydrocarbon chain. This makes it difficult for the molecules to pack closely together, leading to a liquid state at room temperature, such as in vegetable oils.

The length of the hydrocarbon chain can also affect the properties of the fatty acid. Longer chains usually have higher melting points and are more likely to be solid at room temperature. Understanding these differences helps in making informed dietary choices, as each type of fatty acid has different health implications.