Problem 12 - Biology

Question

Saturated fatty acids are so named because they are saturated with (a) hydrogen (b) water (c) hydroxyl groups (d) glycerol (e) double bonds.

Step-by-Step Solution

Answer

Saturated fatty acids are saturated with hydrogen.

Step 1: Understand the Question

The question asks why saturated fatty acids are termed "saturated." We need to identify what they are "saturated" with from the given options.

Step 2: Recall Definition of Saturated Fatty Acids

Saturated fatty acids are a type of fatty acid that have no double bonds between carbon atoms. This means that each carbon atom in the chain is bonded to the maximum possible number of hydrogen atoms.

Step 3: Eliminate Incorrect Options

Review the given options: (a) hydrogen, (b) water, (c) hydroxyl groups, (d) glycerol, (e) double bonds. Since saturated fatty acids have no double bonds and are full of hydrogen atoms, they cannot be saturated with water, hydroxyl groups, glycerol, or double bonds.

Step 4: Choose the Correct Option

Based on the elimination in Step 3, the correct answer is (a) hydrogen, as saturated fatty acids have the maximum number of hydrogen atoms possible for their structure.

Key Concepts

Hydrogen Saturation

Saturated fatty acids get their name from being "saturated" with hydrogen. This means that every available spot on the carbon chain that could hold a hydrogen atom, does have a hydrogen atom. So, in simple terms, these acids have all their carbon atoms connected to hydrogen atoms without missing any spots. This trait makes them fully "hydrogen-saturated," hence the name.

The concept of saturation is important because it affects the properties of the fatty acid. For instance:

• Higher saturation means the fatty acid is more stable and solid at room temperature.
• Hydrogen saturation also influences the melting point, making saturated fatty acids higher in melting point compared to unsaturated ones.

Understanding this can help in knowing why certain fats are solid, like butter, while others, like olive oil, are liquid.

Carbon Atoms

The carbon atoms in a saturated fatty acid chain play a crucial role in its structure. These molecules are primarily long chains of carbon atoms linked together. Each carbon atom can form up to four bonds with surrounding atoms. In saturated fatty acids, each carbon atom forms bonds in the following way:

• Two bonds connect to adjacent carbon atoms in the chain.
• The remaining bonds are attached to hydrogen atoms.

Thus, in the chain of a saturated fatty acid, each carbon atom is "saturated" with hydrogen. This arrangement ensures no carbon atom has room to double-bond with another, maintaining the overall linear and stable structure of the fatty acid.

Double Bonds Absence

A defining characteristic of saturated fatty acids is the absence of double bonds between carbon atoms. Double bonds in fatty acids occur when two carbon atoms share two pairs of electrons, so each carbon atom has fewer hydrogen atoms bonded to it. Saturated fats don't have any double bonds.

The lack of double bonds means that the carbon chains in saturated fatty acids are more flexible and can pack more tightly together. This tight packing contributes to the fats being solid at room temperature, like lard or butter.

• No double bonds: More stable structure.
• Tight packing: Solid at room temperature.

Understanding the absence of double bonds helps explain why saturated fats differ in texture and stability compared to unsaturated fats, which do have such double bonds.