17-The fluid mosaic model of cells membrane: mosaic one respectively). b. What i
ID: 201089 • Letter: 1
Question
17-The fluid mosaic model of cells membrane: mosaic one respectively). b. What is (are) the function(s) of each of this constituents? c. Which property of membrane lipids is the basis for the bilayer nature of cell membranes? d. e. f. Explain with regard to the environment and the inner composition of living cells. Why is the cell membrane a two-dimensional fluid? What is the importance of membrane fluidity? Discuss the different mechanisms involved in homeoviscous adaptation as it happens in various cell types.Explanation / Answer
17.
a. The molecular components making up the fluid parts are: Cholesterol, saturated and unsaturated fatty acids.
The molecular components making up the mosaic part are: Phospholipids, carbohydrate, and protein ( Peripheral and integral proteins)
b. The function of above components are as follows:
Cholesterol: It is randomly distributed along the phospholipid bilayer, it helps to maintain the fluidity of the membrane and holds the phospholipid together so that they don't separate far from each other.
Saturated and unsaturated fatty acids: They also play a role in maintaining the fluidity of the membrane. The kink in unsaturated fatty acids increases the space between phospholipids making it harder to freeze at a lower temperature.
Phospholipid: It contributes to the formation of bilayer structure of Plasma membrane, it is self-assembly in nature. The polar head is hydrophobic in nature and interacts with the aqueous environment and tail forms the inner core portion of the membrane through which molecules enter the cells.
Carbohydrate: They are found on the external surface of the plasma membrane mostly attached to a protein (glycoproteins) and lipids ( glycolipids). They help in cell recognition distinguishing between self and non-self.
Proteins: The cell is made up of two different types of protein integral and peripheral proteins. Integral proteins help in movement of larger molecules across the cell membrane like glucose. Whereas, the peripheral proteins helps in cell signaling and communication.
c. The bilayer nature of cell membrane is contributed by the phospholipids. Generally, the cell is present in an aqueous environment, the polar head of the phospholipid-containing phosphate interacts with water molecules in its vicinity. The tail portion is hydrophobic it tries to hide form aqueous environment and forms the bilayer assembly separating the extracellular and intracellular environment.
d. The two-dimensional fluid structure of cell membrane is due to the self-assembly of the phospholipids with help of cholesterol and fatty acids and allows a selective permeability of the membrane with help of protein channels.
e. The membrane fluidity is contributed by the unsaturated fatty acids and cholesterol. Membrane fluidity prevents any damage to the cell membrane when the temperature is too high and cold. In hotter temperature, the phospholipid molecules separated from each other, cholesterol helps to bind them and prevent separating from each other. In cold temperature the phospholipid molecules come closer and might become stiff and break, leaking the cytoplasm to the surrounding here also cholesterol prevents the molecules from coming too close thereby maintaining the fluidity of the membrane.
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