Select out of the following the correct statement regarding cell membrane.

Question

Work out a cross to explain how normal parents may have a sickle-cell anaemic child.

Answer 1

This question checks basic facts about how the cell membrane is built and how it works, by testing four separate claims one at a time.

Na and K ions move by passive transport: Wrong. These ions are pumped against their concentration gradient by the sodium potassium pump, which burns ATP. That makes it active transport, not passive movement.
Proteins make up 60 to 70% of the membrane: Wrong. Membrane protein content is not fixed at one number, it ranges widely across cell types, roughly from a fifth to four fifths of the membrane mass, so no single percentage band is a safe rule.
Fluid mosaic model given by Singer and Nicolson: Right. This 1972 model describes the membrane as a moving, fluid layer of lipids with proteins scattered through it like tiles in a mosaic, and it is the accepted model taught today.
Lipids arranged with polar heads towards the inner part: Wrong. The polar heads of the lipid bilayer point outward, towards water on both sides of the membrane. The tails, which avoid water, point inward and face each other.

Once each claim is checked against the real biology, only the statement about Singer and Nicolson survives, so option 3 is the correct answer.

Let's summarize:

Sodium and potassium cross the membrane mainly through active transport by the sodium potassium pump.
The fluid mosaic model, given by Singer and Nicolson in 1972, correctly describes the cell membrane.

So the correct statement regarding the cell membrane is option 3, the fluid mosaic model proposed by Singer and Nicolson.

Answer 2

This question checks basic facts about how the cell membrane is built and how it works, by testing four separate claims one at a time.

Na and K ions move by passive transport: Wrong. These ions are pumped against their concentration gradient by the sodium potassium pump, which burns ATP. That makes it active transport, not passive movement.
Proteins make up 60 to 70% of the membrane: Wrong. Membrane protein content is not fixed at one number, it ranges widely across cell types, roughly from a fifth to four fifths of the membrane mass, so no single percentage band is a safe rule.
Fluid mosaic model given by Singer and Nicolson: Right. This 1972 model describes the membrane as a moving, fluid layer of lipids with proteins scattered through it like tiles in a mosaic, and it is the accepted model taught today.
Lipids arranged with polar heads towards the inner part: Wrong. The polar heads of the lipid bilayer point outward, towards water on both sides of the membrane. The tails, which avoid water, point inward and face each other.

Once each claim is checked against the real biology, only the statement about Singer and Nicolson survives, so option 3 is the correct answer.

Let's summarize:

Sodium and potassium cross the membrane mainly through active transport by the sodium potassium pump.
The fluid mosaic model, given by Singer and Nicolson in 1972, correctly describes the cell membrane.

So the correct statement regarding the cell membrane is option 3, the fluid mosaic model proposed by Singer and Nicolson.

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