Fluid mosaic model Knowledge-Based Practice

Questions

1. 1.

   According to the fluid mosaic model, which statement correctly describes the localization and arrangement of carbohydrates in the plasma membrane?

   • A) They are covalently linked to proteins or lipids exclusively on the extracellular leaflet of the bilayer.
   • B) They span the hydrophobic core of the bilayer to form hydrophilic transport channels.
   • C) They are symmetrically distributed across both the cytosolic and extracellular surfaces of the membrane.
   • D) They are confined to the cytosolic leaflet to directly anchor elements of the cytoskeleton.
2. 2.

   According to the fluid mosaic model, why is the spontaneous movement of a phospholipid molecule from one leaflet of the bilayer to the opposite leaflet (flip-flop) an extremely rare event compared to its lateral diffusion?

   • A) Covalent bonds between neighboring phospholipid heads lock them permanently into their respective monolayers.
   • B) The hydrophilic head group must pass through the energetically unfavorable hydrophobic interior of the membrane.
   • C) Integral membrane proteins form a continuous physical barrier that blocks crossing between monolayers.
   • D) Cholesterol molecules form rigid cross-links between the two leaflets that halt vertical movement.
3. 3.

   According to the fluid mosaic model, which characteristic allows integral transmembrane proteins to span the plasma membrane stably?

   • A) Covalent bonds formed between the polypeptide backbone and the phospholipid fatty acid tails
   • B) Continuous hydrophilic domains that interact exclusively with the polar phosphate head groups
   • C) Hydrophobic regions that interact with the fatty acid tails and hydrophilic regions exposed to aqueous environments
   • D) Electrostatic interactions strictly confined to the peripheral surfaces of the lipid bilayer
4. 4.

   According to the fluid mosaic model, how does cholesterol regulate the physical state of animal cell membranes under changing temperatures?

   • A) It promotes crystallization of fatty acid tails at high temperatures and accelerates rapid lipid flip-flop between leaflets at low temperatures.
   • B) It hinders phospholipid movement to reduce fluidity at high temperatures and prevents tight fatty acid packing to maintain fluidity at low temperatures.
   • C) It forms covalent cross-links between integral proteins at high temperatures and dissolves peripheral proteins at low temperatures.
   • D) It completely immobilizes carbohydrate chains at warm temperatures and directly desaturates fatty acid tails at cold temperatures.
5. 5.

   According to the fluid mosaic model, which statement accurately describes the structural organization and behavior of cell membrane components?

   • A) Phospholipids form a rigid monolayer interspersed with fixed proteins that cannot change position.
   • B) Peripheral proteins span the entire bilayer and form an immobilized scaffold that prevents lipid diffusion.
   • C) Carbohydrate chains span both leaflets of the bilayer to anchor proteins permanently in place.
   • D) Integral and peripheral proteins are embedded in or associated with a dynamic phospholipid bilayer, allowing lateral mobility.

Answers and step-by-step solutions appear after you finish the test.