Page 7 - Q & A STPM 2022 Biology

Chapter

3 Membrane Structure

and Transport

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3.1 Fluid-Mosaic Model Semester

Section A Multiple-choice Questions
1
Question 1
Which of the following component of the plasma membrane controls its
fluidity and flexibility?
A Hydrophilic head of the phospholipid molecules
B Oligosaccharide chains attached to the peripheral proteins
C Cholesterol molecules
D Intrinsic proteins

Answer : C
One of the components of the plasma membrane is cholesterol which are
inserted among phospholipid molecules. These molecules increase the
flexibility and stability of membranes. Without it, the membranes break up.

Question 2
Which of the following properties of lecithin are important in the formation
of the structure of a cell membrane?
I Lecithin can be hydrolysed
II Two alcohol groups bind with one fatty acid respectively
III The tips of two hydrocarbon chains are non-polar
IV The tips of the molecule with the phosphate and nitrogen groups are polar
A I and III
B I, III and IV
C II, III and IV
D I, II, III and IV

Answer : B
The most common phospholipid is lecithin which has a positively charged
choline group bound to the phosphate group. It is an important component
of the cell membrane.

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