Question

In the fluid mosaic model of membrane structure:

a. Proteins form an inner layer between two layers of lipid
b. Proteins coat an inner layer of lipids
c. Proteins float in a lipid bilayer
d. Proteins are covalently bonded to the lipid bilayer
e. All of the above are true

Answer 1

In the fluid mosaic model, the statement that proteins float in a lipid bilayer is accurate. Proteins are embedded within the bilayer and can move laterally, but are not covalently bonded to it.

Step-by-step explanation:

In the fluid mosaic model of membrane structure, the correct statement is that proteins float in a lipid bilayer (option c). According to the model proposed by S.J. Singer and G.L. Nicolson in 1972, the plasma membrane structure is a bilayer mainly composed of phospholipids and proteins that can move laterally within the plane of the membrane. The membrane proteins are not covalently bonded to the lipid bilayer, but rather, they are embedded within it, allowing for fluid movement. Integral proteins may span across the entire bilayer or just a part of it, acting as transport proteins and receptors proteins. These proteins and the phospholipids form a dynamic, flexible structure, constituting the 'mosaic' aspect of the model.

Answer 2

Proteins float in a lipid bilayer

Step-by-step explanation:

According to the fluid mosaic model of membrane structure, the membranes are made of the bilayer of lipids. Two layers of amphipathic phospholipids make the bilayer structure in which the non-polar tails of phospholipids of two lipid layers make the inner core of the membrane. Their polar heads are oriented towards the inner and outer surface of the membrane.

Membrane proteins float freely in the bilayer or are joined to some intracellular structure of the cell but are never covalently bonded to the membrane lipids. The integral membrane proteins are inserted into the bilayer while the peripheral membrane proteins are not embedded in the lipid bilayer but are located on the inner or outer surface of the membrane. These proteins are usually bound to exposed regions of integral proteins by noncovalent interactions.