The Ultimate Quiz On Cell Membrane Models

Explanation
The Davson-Danielli model was proposed in 1935.

Explanation
According to Singer and Nicolson's model, the correct sequence of the cell membranes is P-L-L-P. This model, known as the fluid mosaic model, suggests that the cell membrane is composed of a phospholipid bilayer with proteins embedded within it. The P-L-L-P sequence represents the arrangement of the phospholipids and proteins in the membrane, with phospholipids forming the outer and inner layers (P) and proteins interspersed within the layers (L). This model provides a dynamic and flexible structure for the cell membrane, allowing it to regulate the movement of substances in and out of the cell.

Explanation
The fluid mosaic model proposed by Singer and Nicolson in 1972 describes the structure and organization of the cell membrane. According to this model, the cell membrane is composed of a fluid lipid bilayer in which various proteins are embedded, creating a mosaic-like pattern. This model revolutionized our understanding of the cell membrane, highlighting its dynamic nature and the integral role it plays in cellular functions such as transport, signaling, and recognition.

Explanation
Phospholipids are actually present in the cellular membrane, so they cannot be the correct answer. Phospholipids are a major component of the lipid bilayer that forms the structure of the cellular membrane. They have a hydrophilic (water-loving) head and hydrophobic (water-fearing) tails, which allows them to arrange themselves in a double layer, with the hydrophilic heads facing the water-based environment inside and outside the cell, and the hydrophobic tails facing each other in the middle. This arrangement provides a barrier that controls the movement of molecules in and out of the cell.

Explanation
Integral proteins are membrane proteins that are embedded within the lipid bilayer of the cell membrane. These proteins have hydrophobic regions that interact with the hydrophobic interior of the lipid bilayer, anchoring them in place. Integral proteins play a crucial role in active transport, where they act as transporters or pumps to move molecules or ions against their concentration gradient across the cell membrane. They undergo conformational changes to transport substances across the membrane, requiring energy in the form of ATP. Therefore, integral proteins are the membrane structures that function in active transport.

Explanation
According to the fluid mosaic model, proteins are the type of molecule that spans the membrane from its inner to outer surface. Proteins are embedded within the phospholipid bilayer of the cell membrane and play a crucial role in various cellular processes such as transport, signaling, and cell adhesion. They have hydrophilic and hydrophobic regions that allow them to interact with both the aqueous environment inside and outside the cell, making them well-suited for spanning the entire membrane.

Explanation
Osmosis is the correct answer because it refers to the diffusion of water across a concentration gradient. In osmosis, water molecules move from an area of lower solute concentration to an area of higher solute concentration, in order to equalize the concentration on both sides of the membrane. This process is important for maintaining the balance of water and solutes in living organisms. Exocytosis, on the other hand, is the process by which cells release substances from inside the cell to the outside, and it is not related to the diffusion of water.

Explanation
Glycoproteins and glycolipids are types of carbohydrates that are found in the membrane. Glycoproteins are proteins that have attached carbohydrate chains, while glycolipids are lipids that have attached carbohydrate chains. These carbohydrates play important roles in cell recognition, cell signaling, and cell adhesion. Phospholipids and lipids, although important components of the membrane, do not contain carbohydrates. Hydrophobic molecules are not carbohydrates and are not typically found in the membrane. Therefore, the correct answer is glycoproteins and glycolipids.

Explanation
Stearic acid is a type of fatty acid that is commonly found in various foods and oils. However, it is not a type of lipid that is typically found in lipid-linked proteins. Lipid-linked proteins are proteins that are attached to lipids, such as glycosylphosphatidylinositol (GPI), through a covalent bond. Palmitic acid and myristic acid are examples of fatty acids that can be found in lipid-linked proteins. GPI is a type of lipid that is commonly found in lipid-linked proteins and is involved in anchoring proteins to the cell membrane. Therefore, stearic acid is the correct answer as it is the only option that is not an example of a lipid found in lipid-linked proteins.

Explanation
The other name for the Danielli and Davson model is the Lipo-protein sandwich model. This model proposes that the cell membrane consists of a phospholipid bilayer with protein layers on both sides, forming a sandwich-like structure. The proteins act as a barrier and provide stability to the membrane.