Chapter 3 - Section 3.2 - The Cell Surface - Apply What You Know - Page 83: 2

If the plasma membrane were primarily made of a hydrophilic substance such as carbohydrates, it would result in a highly permeable and unstable membrane, leading to a loss of essential membrane functions. This scenario would primarily exemplify the major theme of **"Structure and Function"** at the end of Chapter 1 of many biology textbooks. Here's how this situation relates to the theme of structure and function: 1. **Structure and Function:** The plasma membrane's structure is essential for its function as a selectively permeable barrier that separates the cell's interior from the external environment. The plasma membrane is primarily composed of lipids, including phospholipids, which have hydrophilic heads and hydrophobic tails. This structure creates a stable bilayer in which the hydrophobic tails are shielded from water, while the hydrophilic heads interact with the aqueous environment. If the plasma membrane were primarily made of hydrophilic carbohydrates, it would disrupt the integrity of the membrane's structure. Carbohydrates are hydrophilic, meaning they have an affinity for water and do not form stable, hydrophobic barriers. As a result, the membrane would lose its ability to regulate the passage of ions and molecules, leading to uncontrolled leakage and entry of substances. This would severely impair the membrane's function as a boundary, compromising cellular homeostasis and function. 2. **Selective Permeability:** One of the critical functions of the plasma membrane is to maintain selective permeability, allowing only specific substances to enter or exit the cell. This selectivity is achieved through the lipid bilayer's hydrophobic core, which acts as a barrier to hydrophilic molecules. If the membrane were primarily composed of hydrophilic carbohydrates, it would be unable to provide this selective permeability, and the cell would be unable to control what enters and exits. 3. **Homeostasis:** The plasma membrane's ability to maintain a stable internal environment (homeostasis) is essential for the cell's survival and function. A membrane primarily composed of hydrophilic carbohydrates would compromise homeostasis by allowing unregulated movement of water and solutes in and out of the cell. This would disrupt cellular processes and ultimately lead to cell dysfunction and potentially cell death. In summary, a plasma membrane primarily composed of hydrophilic carbohydrates would exemplify the major theme of "Structure and Function" by highlighting how the structure of the membrane is intricately linked to its function in maintaining cellular integrity, selective permeability, and homeostasis. Such a scenario would underscore the importance of the plasma membrane's lipid bilayer structure in supporting these vital cellular functions.

If the plasma membrane were primarily made of a hydrophilic substance such as carbohydrates, it would result in a highly permeable and unstable membrane, leading to a loss of essential membrane functions. This scenario would primarily exemplify the major theme of **"Structure and Function"** at the end of Chapter 1 of many biology textbooks. Here's how this situation relates to the theme of structure and function: 1. **Structure and Function:** The plasma membrane's structure is essential for its function as a selectively permeable barrier that separates the cell's interior from the external environment. The plasma membrane is primarily composed of lipids, including phospholipids, which have hydrophilic heads and hydrophobic tails. This structure creates a stable bilayer in which the hydrophobic tails are shielded from water, while the hydrophilic heads interact with the aqueous environment. If the plasma membrane were primarily made of hydrophilic carbohydrates, it would disrupt the integrity of the membrane's structure. Carbohydrates are hydrophilic, meaning they have an affinity for water and do not form stable, hydrophobic barriers. As a result, the membrane would lose its ability to regulate the passage of ions and molecules, leading to uncontrolled leakage and entry of substances. This would severely impair the membrane's function as a boundary, compromising cellular homeostasis and function. 2. **Selective Permeability:** One of the critical functions of the plasma membrane is to maintain selective permeability, allowing only specific substances to enter or exit the cell. This selectivity is achieved through the lipid bilayer's hydrophobic core, which acts as a barrier to hydrophilic molecules. If the membrane were primarily composed of hydrophilic carbohydrates, it would be unable to provide this selective permeability, and the cell would be unable to control what enters and exits. 3. **Homeostasis:** The plasma membrane's ability to maintain a stable internal environment (homeostasis) is essential for the cell's survival and function. A membrane primarily composed of hydrophilic carbohydrates would compromise homeostasis by allowing unregulated movement of water and solutes in and out of the cell. This would disrupt cellular processes and ultimately lead to cell dysfunction and potentially cell death. In summary, a plasma membrane primarily composed of hydrophilic carbohydrates would exemplify the major theme of "Structure and Function" by highlighting how the structure of the membrane is intricately linked to its function in maintaining cellular integrity, selective permeability, and homeostasis. Such a scenario would underscore the importance of the plasma membrane's lipid bilayer structure in supporting these vital cellular functions.