Which of the following is a principle of the fluid mosaic model of the plasma membrane structure?
The lipid bilayer is a solid at body temperature, thus protecting the cell.
All proteins associated with the cell membrane are contained in a fluid layer on the outside of the cell.
Phospholipids form a bilayer that is largely impermeable to water-soluble molecules.
Phospholipids consist of a polar head and a nonpolar tail made of three fatty acid chains.
The Correct Answer is C
A. The lipid bilayer is a solid at body temperature, thus protecting the cell: The lipid bilayer is not solid at body temperature; it is fluid, allowing lateral movement of lipids and proteins, which is essential for membrane flexibility and function.
B. All proteins associated with the cell membrane are contained in a fluid layer on the outside of the cell: Membrane proteins are not restricted to the outer surface. They can be integral, spanning the membrane, or peripheral, attached to either the inner or outer surface, participating in transport, signaling, and structural support.
C. Phospholipids form a bilayer that is largely impermeable to water-soluble molecules: The phospholipid bilayer acts as a barrier to most polar and charged molecules while allowing nonpolar molecules to diffuse through. This selective permeability is a core principle of the fluid mosaic model.
D. Phospholipids consist of a polar head and a nonpolar tail made of three fatty acid chains: Phospholipids have a polar head and two, not three, nonpolar fatty acid tails. This structure creates the amphipathic nature of the membrane, contributing to the bilayer formation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. A long fatty acid chains: Triglycerides with long fatty acid chains can be either saturated or unsaturated. The chain length affects melting point to some extent but does not solely determine whether the fat is a solid or liquid at room temperature.
B. Saturated fatty acids: Saturated triglycerides have no double bonds, making their fatty acid chains tightly packed. This structure leads to higher melting points, so they are generally solid at room temperature, as seen in butter or lard.
C. Unsaturated fatty acids: Unsaturated triglycerides contain one or more double bonds in their fatty acid chains, which introduce kinks that prevent tight packing. This structure lowers their melting point, making them liquid at room temperature and therefore classified as oils.
D. A high water content: Triglycerides are hydrophobic molecules that do not mix with water. Their classification as oils or fats depends on the degree of saturation of fatty acids, not water content, since triglycerides themselves contain virtually no water.
Correct Answer is D
Explanation
A. The osmolarity decreases and the water concentration increases: Increasing solute concentration does not decrease osmolarity; higher solute levels actually increase osmolarity while reducing free water concentration.
B. The osmolarity decreases and the water concentration decreases: Increasing solute concentration raises osmolarity rather than lowering it, even though water concentration does decrease.
C. The osmolarity increases and the water concentration increases: While osmolarity rises with higher solute concentration, the water concentration does not increase; it decreases as water molecules are effectively bound by solutes.
D. The osmolarity increases and the water concentration decreases: Higher solute concentration increases osmolarity, creating a stronger driving force for water movement. At the same time, the concentration of free water decreases because more water molecules are associated with solutes.
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