Fluid mosaic model was proposed by Singer and Nicolson. According to t...
The correct answer is 3. Glycoproteins on the cell surface are necessary for immune recognition.
This is the correct answer because the passage discusses how some membrane lipids and integral proteins remain bound to oligosaccharides (a type of sugar molecule) that project into the extracellular fluid. This is a reference to glycoproteins, which are proteins that have carbohydrates attached to them. These glycoproteins are vital for immune recognition, as they help the immune system distinguish between self and non-self cells.
Option 1 is incorrect because the passage doesn't mention lipid rafts. Option 2 is also incorrect because, while cholesterol is a component of cell membranes, the passage specifies that the central part of the membrane is made of a lipid bilayer of phospholipids, not cholesterol. Option 4 is incorrect because it includes the incorrect options 1 and 2.
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Fluid mosaic model was proposed by Singer and Nicolson. According to t...
Structure of Membranes
The structure of biological membranes is commonly described by the fluid mosaic model, which was proposed by Singer and Nicolson in 1972. This model provides a comprehensive understanding of the arrangement and composition of cell membranes.
Lipid Bilayer
According to the fluid mosaic model, the central component of cell membranes is a lipid bilayer. This bilayer is primarily composed of phospholipids, which have a polar head group and non-polar tails. The polar head groups face the outside of the membrane, interacting with the aqueous environment, while the non-polar tails are positioned towards the inside of the membrane, forming a hydrophobic interior.
Integral Proteins
Embedded within the lipid bilayer are integral or intrinsic proteins. These proteins are firmly bound to the membrane and cannot be separated from it without disrupting the membrane structure. Some integral proteins span the entire lipid bilayer, extending from one side to the other. These large globular proteins are known as transmembrane proteins and play important roles in various cellular processes, such as transport and signal transduction.
Peripheral Proteins
In addition to integral proteins, there are also superficially attached proteins known as extrinsic or peripheral proteins. Unlike integral proteins, peripheral proteins are not embedded within the lipid bilayer and can be easily removed from the membrane. They are often associated with the inner or outer surface of the membrane and participate in various cellular functions, such as cell signaling and enzymatic activity.
Glycoproteins
Some membrane lipids and integral proteins are bound to oligosaccharides, forming glycoproteins. These oligosaccharides project into the extracellular fluid, providing a protective layer and participating in cell recognition and immune responses. Glycoproteins play crucial roles in cell-cell communication, immune recognition, and the binding of certain molecules.
Explanation of Correct Answer
The correct answer to the given question is option 'D' - Glycoproteins on the cell surface are necessary for immune recognition. This statement aligns with the information provided in the description of glycoproteins in the fluid mosaic model. Glycoproteins on the cell surface are involved in immune recognition processes, allowing cells to interact with each other and with components of the immune system. These glycoproteins play a crucial role in the recognition of foreign antigens and the coordination of immune responses.
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