N5S3 - Transport across Cell Membranes - 1.3

Question 1

Why are cell membranes selectivley permeable?

Answer 1

It is selectively permeable because of its structure. It’s made up of a phospholipid bilayer (hydrophobic tails facing inside). This structure stops large molecules from easily diffusing through it.

Question 2

Name and describe three of the jobs proteins in the cell membrane have

Answer 2

1. Some proteins form channels making pores in the membrane that allow small molecules to move through passively.
2. Some proteins are partially embedded in the phospholipid bilayer or rest on its surface. They work as chemical receptors or enzymes for reactions.
3. Others act as carrier proteins for the process of active transport of materials across the membrane

Question 3

State and describe three conditions that can disrupt the structure of the cell membrane

Answer 3

• High Temperature - denatures proteins
• Ethanol - dissolves the phospholipids (fat)
• Osmotic imbalance