Problem 29 - Objective Biology for NEET

Question

What is the number of carbon atoms which the palmitic and arachidonic acid contain (including carboxyl carbon)? (a) 16,19 (b) 15,19 (c) 16,20 (d) 18,20

Step-by-Step Solution

Answer

The answer is (c) 16,20. Palmitic acid contains 16 carbon atoms, and arachidonic acid contains 20 carbon atoms.

Step 1: Identify the fatty acids structure

First, know the structure of the fatty acids mentioned. Palmitic acid and Arachidonic acid are both fatty acids. The former is considered a saturated fatty acid while the latter is a polyunsaturated fatty acid. Both of their structures include a carboxyl group (-COOH).

Step 2: Determine the content of Palmitic acid

Second, determine the content of Palmitic acid. Palmitic acid is mainly composed of 16 carbon atoms, including the carboxyl carbon.

Step 3: Determine the content of Arachidonic acid

Lastly, determine the content of Arachidonic acid. Arachidonic acid possesses 20 carbon atoms, including the carboxyl carbon.

Key Concepts

Understanding Palmitic Acid

Palmitic acid is a type of fatty acid that is common in both animals and plants. It is known for having a chain consisting of 16 carbon atoms. This structure makes it a saturated fatty acid, which means that it contains no double bonds between its carbon atoms. The absence of these double bonds ensures that every available carbon bond is filled with hydrogen atoms. This is one of the characteristics that impart solid properties at room temperature to saturated fats like palmitic acid. Including the terminal carboxyl group (-COOH), which is essential for many biochemical processes, palmitic acid is foundational in the structure of many lipids.

An Introduction to Arachidonic Acid

Arachidonic acid differs significantly from palmitic acid. It is a polyunsaturated fatty acid, characterized by having multiple double bonds along its chain. Specifically, arachidonic acid has a chain of 20 carbon atoms and 4 double bonds. The presence of these double bonds lends flexibility to the molecule, which can affect the fluidity of the fats in biological membranes. Additionally, like palmitic acid, it includes a carboxyl group at one end. Arachidonic acid is important in the human body as it is a precursor to various signaling molecules, playing pivotal roles in inflammation and immunity.

Characteristics of Saturated Fatty Acids

Saturated fatty acids like palmitic acid are a category of fats in which all of the carbon atoms are saturated with hydrogen atoms. In other words, they contain no double bonds between the carbon atoms of their hydrocarbon chain. This saturation is the reason for their solid state at room temperature. Saturated fatty acids are typically found in animal fats and some plant oils. Healthwise, excessive consumption of saturated fatty acids has been linked to heart disease, highlighting the need for moderation in dietary intake.

The Role of Polyunsaturated Fatty Acids

Polyunsaturated fatty acids, such as arachidonic acid, are known for their multiple double bonds in their carbon chains. These double bonds introduce kinks to the structure, keeping these fats liquid at room temperature. Such properties are crucial in maintaining the fluidity of cell membranes. This category of fatty acids includes essential fatty acids that the body cannot synthesize but must obtain through diet. They are found in large quantities in fish, nuts, and seeds and are essential for normal cell function and eicosanoid production, influencing inflammation and cell signaling.

The Importance of the Carboxyl Group

The carboxyl group (-COOH), essential in both palmitic and arachidonic acids, plays a critical role in organic chemistry. Found at the terminal end of fatty acids, it imparts acidity, making these molecules capable of participating in various chemical reactions. In the human body, the carboxyl group enables fatty acids to attach to glycerol, forming triglycerides, which are vital for storing energy. Additionally, it allows the formation of phospholipids, key components of cell membranes. Understanding the role of carboxyl groups can help to comprehend the diversity of functions that fatty acids can perform in biological systems.