Answer:
The cell membrane is semi-permeable. (or selectively permeable). The unique structure of the cell membrane allows small substances (like oxygen or carbon dioxide) to easily pass through.
Step-by-step explanation:
The principal components of the plasma membrane are lipids (phospholipids and cholesterol), proteins, and carbohydrate groups that are attached to some of the lipids and proteins. A phospholipid is a lipid made of glycerol, two fatty acid tails, and a phosphate-linked head group.