Question

Predict the likely effect on the ability of substance L to enter the cells if substance L is attached to a large protein instead of free in the culture

Answer 1

If substantial L is bound to a large protein, rather than being free in the culture, its ability to enter a cell will be hampered and it is possible that it will not be able to enter at all.

Why would this happen?

• Cell membranes are very selective.
• Large molecules are not easily accepted by membranes.

For a substance to enter a cell, it will need to pass through plasma membranes, which are extremely selective in allowing this entry to occur.

When the substance is linked to a large protein, it becomes a molecule that is too large to pass through the membrane receptors and too complex to pass through the selectivity of the membranes, which opt for simpler molecules.

Answer 2

The nature of the cell membrane is semi- permeable. This means that it allows some of the molecules or ions to pass through it but others cannot pass through it.

The information in the question shows that the substance L moves inside the cell by passive transport. As it moves through the help of large proteins we can say that these proteins are channel or carrier proteins.

We can say that the substance L is moving by passive transport because as the concentration of L increases outside the cell, the rate of its entry into the cell also increases i.e along the concentration gradient.