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Multiple Choice
Which of the following statements about the cell membrane is TRUE?
A
The cell membrane is rigid and impermeable to all molecules.
B
Integral membrane proteins are only found on the exterior surface of the membrane.
C
The cell membrane is composed primarily of a phospholipid bilayer with embedded proteins.
D
Cholesterol is absent from all eukaryotic cell membranes.
Verified step by step guidance
1
Step 1: Understand the structure of the cell membrane. The cell membrane is primarily composed of a phospholipid bilayer, which consists of hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails. This bilayer provides fluidity and flexibility to the membrane.
Step 2: Recognize the role of embedded proteins. Integral membrane proteins are embedded within the phospholipid bilayer and can span the entire membrane or be partially embedded. These proteins are involved in various functions such as transport, signaling, and structural support.
Step 3: Clarify the role of cholesterol in eukaryotic cell membranes. Cholesterol is present in eukaryotic cell membranes and plays a crucial role in maintaining membrane fluidity and stability, especially under varying temperature conditions.
Step 4: Evaluate the incorrect statements. The cell membrane is not rigid; it is flexible and selectively permeable, allowing certain molecules to pass through. Integral membrane proteins are not limited to the exterior surface; they can be found throughout the membrane. Cholesterol is not absent from eukaryotic membranes; it is an essential component.
Step 5: Identify the correct statement. Based on the information above, the correct statement is: 'The cell membrane is composed primarily of a phospholipid bilayer with embedded proteins.' This accurately describes the structure and composition of the cell membrane.