## **Core Concept**
The incorporation of polyunsaturated fatty acids (PUFAs) into the plasma membrane affects its fluidity and structure. PUFAs are known to increase membrane fluidity due to their kinked tails, which prevent tight packing of phospholipid molecules.

## **Why the Correct Answer is Right**
The correct answer, **D. Increased fluidity**, is right because PUFAs have multiple double bonds that create kinks in their tails. These kinks prevent the phospholipid molecules from packing tightly together, thereby increasing the space between them and making the membrane more fluid. This is crucial for maintaining proper membrane function, including transport, signaling, and cell division.

## **Why Each Wrong Option is Incorrect**
- **Option A: Decreased fluidity**. This is incorrect because PUFAs increase, rather than decrease, membrane fluidity due to their structural characteristics.
- **Option B: Increased melting point**. This is incorrect because the presence of double bonds in PUFAs actually decreases the melting point of the membrane, contributing to increased fluidity at lower temperatures.
- **Option C: No change**. This is incorrect because PUFAs do have an effect on membrane fluidity; they increase it.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that changes in membrane fluidity can affect the functioning of embedded proteins, including receptors and transport proteins. For example, alterations in membrane fluidity can impact the activity of certain enzymes and receptors, which is relevant in various disease states and pharmacological interventions.

## **Correct Answer:** . Increased fluidity