Question

The cell membranes are mainly composed of (a) fats (b) proteins (c) phospholipids (d) carbohydrates

Short answer

Cell membranes are mainly composed of phospholipids.

Step-by-step solution

Identify Components of Cell Membranes

Cell membranes are complex structures that primarily consist of a few key molecules. While they do contain fats, proteins, and carbohydrates to some extent, the primary structural component is phospholipids.

Understand the Structure of Phospholipids

Phospholipids are unique molecules that have a hydrophilic (water-attracting) 'head' and two hydrophobic (water-repelling) 'tails'. This allows them to form a bilayer, which is essential for the structural integrity and function of the cell membrane.

Recognize the Role of the Phospholipid Bilayer

The phospholipid bilayer serves as the foundational framework of the cell membrane, creating a semi-permeable structure that controls the movement of substances in and out of the cell.

Select the Correct Primary Component

Based on the structure and composition of cell membranes predominantly being phospholipids, answer (c) phospholipids is correct.

Key concepts

Phospholipids

The cell membrane is predominantly made up of components known as phospholipids. These are specialized molecules that play an essential role in maintaining the structural integrity of the cell. Each phospholipid consists of two main parts: a hydrophilic "head" and two hydrophobic "tails".
The hydrophilic head is attracted to water, meaning it is polar. This is crucial as it helps the cell interact with the aqueous environment both inside and outside. In contrast, the hydrophobic tails repel water, allowing them to align themselves away from the watery environments, forming a double layer known as the phospholipid bilayer. This arrangement is fundamental in making the membrane selectively permeable.
Due to their unique structure, phospholipids automatically align in a way that will form the basis of the cell membrane, effectively separating the interior of the cell from its external environment, while allowing fluid dynamics and flexibility.

Proteins in Cell Membranes

Proteins embedded within the cell membrane are essential for its functionality and flexibility. These proteins can either be peripheral or integral. Integral proteins span the entire membrane and are involved in transporting substances across, acting as channels or carriers. They play a crucial role in allowing the cell to communicate and exchange substances with its environment.
Peripheral proteins, on the other hand, are attached to the surface of the membrane. They assist in maintaining the structure of the membrane by anchoring the integral proteins, and participate in various signaling pathways. Proteins, as a whole, contribute significantly to the dynamic nature of the membrane, allowing it to constantly adjust and respond to its surroundings.
Together, these proteins ensure that while the membrane maintains a selective barrier, it also facilitates the necessary transport and signaling functions needed for the cell's survival and adaptation.

Structure of Cell Membranes

The structure of cell membranes is a marvel of biological engineering, crucial for life as we know it. At its core, the membrane is primarily composed of a phospholipid bilayer, which forms the basic structural framework. This bilayer is flexible, allowing it to self-repair and mold around various shapes needed by the cell.
Additionally, the cell membrane's dynamic nature is enhanced by the presence of proteins, cholesterol, and carbohydrates. Cholesterol molecules interspersed among the phospholipids provide stability and fluidity under varied temperatures. Carbohydrates attached to proteins and lipids form complex structures known as glycoproteins and glycolipids, serving critical roles in cell recognition and signaling.
All these components work coherently to ensure that the membrane is not just a barrier but a highly functional interface that regulates substance flow and communication with the external environment, ultimately ensuring the cell's functionality and viability.