Consider the following statements about the cell membrane or plasma membrane:
A: Plasma membrane is mainly composed of double layer amphipathic phospholipid molecules and it is semipermeable to the hydrophilic and hydrophobic molecules.
R: Both outer faces of the plasma membrane is hydrophilic due to presence of polar phosphate group and inner core of the membrane is hydrophobic so, neither ionic nor non-ionic molecule move freely across the membrane without facing unfavourable molecular environment.
Select the correct answer using the codes given below:
Both A and R, are true and R is the correct explanation of A.
Incorrect AnswerBoth A and R, are true but R is not the correct explanation of A.
Incorrect AnswerA is correct but R is incorrect.
Incorrect AnswerA is incorrect but R is correct.
Correct AnswerExplanation:
Plasma membrane :
- Plasma membrane is not a semipermeable membrane; it is a selective permeable membrane.
- Semipermeable membrane does not have the ability to ‘discriminate’ between the particles of the same size to let through, while a selective permeable membrane can actively select some particle to pass or block regardless of similarity in the size.
- Selective permeability may need to use energy to transport some molecules against the physical potential barriers.
- Although all bio membranes have the same basic phospholipid bilayer structure and certain common functions, each type of cellular membrane also has certain distinctive activities determined largely by the unique set of proteins associated with that membrane.
- Phospholipids Are the Main Lipid Constituents of Most Bio membranes, the most abundant lipid components in most membranes are phospholipids, which are amphipathic molecules (i.e., they have a hydrophilic and a hydrophobic part).
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By: Parvesh Mehta