Cells Exchange Materials (Chapter 4)

Question 1

5) What is a differentially permeable membrane/? How would such a membrane differ from one that is completely permeable?

Answer 1

Differentially permeable membranes allow certain ions and molecules to pass through but restrict the movement of others. A completely permeable membrane allows any molecule to pass through.

Question 2

6) What is osmosis? In your answer explain what is meant by ‘osmotic pressure.’

Answer 2

Osmosis is the process in which a liquid passes through a membrane whose pores permit the passage of solvent molecules but are too small for the larger solute molecules to pass through. The pressure required to achieve osmotic equilibrium is known as the osmotic pressure. Note that the osmotic pressure is the pressure required to stop osmosis, not to sustain it.

Question 3

7) What ‘carriers’ are involved in carrier-mediated transport? Explain the role of the carrier in this type of transport.

Answer 3

In carrier-mediated transport, proteins in the cell membrane bind to molecules to be transported and help their passage across the membrane.