B1.1.10 Difference between saturated, monounsaturated and polyunsaturated fatty acids Notes

The Structure of Fatty Acids: A Quick Overview

1. All fatty acids share a common structure: a long hydrocarbon chain (a chain of carbon atoms bonded to hydrogen) with a carboxyl group (-COOH) at one end. However, these chains can vary in two key ways:
   1. Length: The number of carbon atoms in the chain (typically between 14 and 20 in biological systems).
   2. Saturation: The number and position of double bonds between carbon atoms.

1. Saturated fatty acids: No double bonds. Every carbon atom is fully "saturated" with hydrogen atoms.
   1. Unsaturated fatty acids: One or more double bonds between carbon atoms. These are further divided into:
   2. Monounsaturated fatty acids (MUFA): Contain one double bond.
   3. Polyunsaturated fatty acids (PUFA): Contain two or more double bonds.

Saturated Fatty Acids: The Straight Chains

Characteristics

1. No double bonds: A rigid, linear structure.
2. High melting point: Tightly packed molecules require more energy (heat) to separate, making saturated fats solid at room temperature.
3. Sources: Found in animal fats (e.g., butter, lard) and some plant oils like coconut oil.

Biological Role

1. Saturated fats are ideal for long-term energy storage and thermal insulation in animals.
2. For example, marine mammals like whales rely on blubber, rich in saturated fatty acids, to retain heat in cold waters.

Monounsaturated Fatty Acids: The First Bend

Characteristics

1. One double bond: The kink reduces the molecule’s ability to stack.
2. Moderate melting point: MUFAs are typically liquid at room temperature but may solidify when cooled.
3. Sources: Found in plant-based oils like olive oil, avocado oil, and nuts.

Biological Role

1. MUFAs are common in plant oils, which are liquid at room temperature.
2. These oils provide energy storage in seeds and are easier to mobilize during germination.