Question

Carbohydrates of the plasma membrane a. are bonded to a protein or lipid. b. are located on the outer surface of the plasma membrane. c. can function as cell markers for recognition by other cells. d. All of the above are true of the carbohydrates. e. Only a and c are true

Short answer

D. All of the above are true of the carbohydrates.

Step-by-step solution

Understanding Plasma Membrane

The first step is to understand what is a plasma membrane. It is a biological membrane that separates the interior of all cells from the outside environment. Carbohydrates have crucial functions in plasma membranes - they are typically found on the outer surface where they are covalently bound to proteins (forming glycoproteins) or lipids (forming glycolipids). This makes them cell-identifying markers that aid in cell recognition and adhesion.

Analyzing the Options

Now, let's analyze the options. Considering the understanding of plasma membranes and the role of the carbohydrates, let's analyze each option. \nA. Carbohydrates are indeed bonded to a protein or lipid, making this statement true.\nB. Carbohydrates are located on the outer surface of the plasma membrane, making this statement also true. \nC. Carbohydrates also function as cell markers for recognition by other cells, making this statement true as well.\nIf all the options A, B and C are true, then the option D (All of the above are true of the carbohydrates) is also true.

Drawing Conclusion

Comparing all the options, it becomes clear that option D - which states that all of the above are true - is indeed correct. Therefore, option E is wrong since it denies the correctness of statement B which we established to be true.

Key concepts

Carbohydrates

Carbohydrates in the plasma membrane play a vital role in cellular interactions. These sugars are linked covalently to proteins and lipids, forming complex molecules involved in cell function.
Carbohydrates are not simply attached for structural purposes but hold critical biological significance. They are located on the outer surface of the plasma membrane, where they participate in various cellular processes.
They help in stabilizing the membrane structure and act as a barrier to undesirable substances. Through the formation of glycoproteins and glycolipids, carbohydrates facilitate communication within the cell environment.

Cell Recognition

Cell recognition is a fundamental process in which cells identify and interact with each other. This interaction is crucial for maintaining healthy cellular functions and regulating cellular behavior.
The carbohydrates on the plasma membrane are key players in this process. By acting as cell markers, they allow cells to differentiate between one another, which is essential for processes like immune response and growth.
These carbohydrates ensure cells can recognize foreign cells, signaling the immune system to respond appropriately, thereby protecting the body from potential threats.

Glycoproteins

Glycoproteins are proteins attached with carbohydrate chains, located prominently on the cell membrane. These molecules are involved in various cellular activities, primarily focusing on cell-to-cell interactions.

• They assist in recognizing and binding to specific molecules.
• Glycoproteins play a role in immune responses by marking characteristics of a cell.
• In hormonal activities, they function as receptors.

These versatile functions highlight their importance in maintaining health and signaling within the body, contributing to the complexity and effectiveness of cellular communication.

Glycolipids

Glycolipids combine lipids with carbohydrate groups to form structures fundamental to the cellular membrane's integrity. Predominantly found on the external surface of the plasma membrane, they are crucial for cellular identification and communication.

• They contribute to the stability of the cell membrane.
• Glycolipids play a significant role in tissue formation and immune response.
• By facilitating cell recognition, they help organize cells into tissues and communicate with hormones and neurotransmitters.

Through these processes, glycolipids are pivotal in managing how cells interact with each other and the external environment.