Which of the following do not affect membrane fluidity

Question

BlackTom AI · Accepted Answer

The question asks which options do not affect membrane fluidity.
Option 1: Peripheral membrane proteins and Proteoglycans. This combination is not a primary determinant of the lipid bilayer's fluidity. Peripheral membrane proteins associate with the surface, and proteoglycans are typically extracellular components; neither directly modulates the lipid packing or phase behavior that governs fluidity. Therefore, this choice correctly identifies factors that do not govern membrane fluidity in the classic sense.
Option 2: Peripheral membrane proteins. While these proteins can influence membrane organization or curvature in some contexts, their presence on the surface does not inherently dictate the fatty acid composition or cholesterol interactions that control fluidity; thus, this option is not the best answer to the question as stated, since it narrows to a subset.
Option 3: Temperature and Presence of cholesterol. Temperature has a well-established effect: increasing temperature generally increases fluidity, while decreasing temperature rigidifies membranes. Cholesterol modulates fluidity in a temperature-dependent manner, preventing extreme tight packing at low temperatures and reducing excessive movement at high temperatures. This option correctly describes factors that do affect fluidity, making it an incorrect answer to the question.
Option 4: Presence of cholesterol. Cholesterol is a key regulator of membrane fluidity, smoothing transitions between gel and fluid phases and maintaining membrane order. By itself, this statement is true about influencing fluidity, so it should not be selected as a factor that does not affect fluidity.
Option 5: Temperature. As noted above, temperature directly influences lipid mobility and phase state, so it certainly affects membrane fluidity. This makes it an incorrect choice for the question.
Option 6: Proteoglycans. Proteoglycans reside largely outside the lipid bilayer and contribute to the extracellular matrix structure and signaling, not to the lipid bilayer’s fluidity. While they can affect cell-cell interactions or membrane organization indirectly, they do not govern the intrinsic fluidity of the lipid bilayer itself, aligning with why this option does not affect fluidity.
In summary, the core concept is that membrane fluidity is primarily controlled by lipid composition, cholesterol, and temperature, whereas peripheral surface-associated proteins and proteoglycans do not set the bilayer’s fluidity in the classic biophysical sense. This aligns with selecting Peripheral membrane proteins and Proteoglycans as the factors that do not affect membrane fluidity.

Which of the following do not affect membrane fluidity单项选择题

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