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The fluid mosaic model of the membrane describes the membrane as
a. containing a significant quantity of water in the interior.
b. composed of fluid phospholipids on the outside and protein on the inside.
c. composed of protein on the outside and fluid phospholipids on the inside.
d. made of proteins and lipids that can freely move.
Introduction:
The fluid mosaic model of plasma membrane was proposed by Singer and Nicolson. They stated that plasma membrane is a semipermeable membrane that allows only selective particles to go in and out of the cell. It is made of phospholipids and proteins, which are embedded within the lipid bilayer.
Answer to Problem 1U
Correct answer:
The fluid mosaic model describes the plasma membrane as a mosaic of proteins floating in a layer of lipids. Therefore, option d is correct.
Explanation of Solution
Reason for the correct statement
The fluid mosaic model explains that proteins are embedded within the lipid bilayer. The lipid bilayer provides fluidity and elasticity to the membrane, and it consists of transmembrane proteins floating in the lipid bilayer. It helps in transportation and communication across the membrane. The lipid bilayer also contains interior proteins that help to maintain the shape of the membrane.
Option d is given as “made of proteins and lipids that can move freely.”
As “the plasma membrane is made of phospholipids bilayer in which proteins are embedded and provides flexibility as well as helps in transportation and communication across the membrane,” option d is the right answer.
Reasons for the incorrect statements:
Option a is given as “containing a significant quantity of water in the interior.”
The plasma membrane is made of a lipid bilayer and proteins that provide stability to the membrane. So, it is a wrong answer.
Option b is given as “composed of fluid phospholipids inside and proteins outside.”
The plasma membrane is composed of phospholipids with the hydrophobic tails inside and hydrophilic heads outside, whereas intrinsic proteins are embedded in the lipid bilayer and extrinsic proteins are present outside the lipid bilayer. So, it is a wrong answer.
Option c is given as “composed of proteins on the outside and fluid phospholipids on the inside.”
The lipid bilayer is arranged in a specific manner such as its hydrophobic tail is present inside and hydrophilic head is present outside. Similarly, there are two types of proteins present in the plasma membrane: intrinsic proteins which are present inside the lipid bilayer and extrinsic proteins, which are present outside the lipid bilayer. So, it is a wrong answer.
Hence, options a, b, and c are incorrect.
Plasma membrane is called semipermeable membrane as it allows only selective particles to go in and out of the cell and it helps in protection of cell from several injuries. It prevents infections by blocking the entry of disease-causing microorganisms.
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Chapter 5 Solutions
Biology
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Concepts of BiologyBiologyISBN:9781938168116Author:Samantha Fowler, Rebecca Roush, James WisePublisher:OpenStax College