The correct answer is: C. 70% proteins and 30% lipids
Biological membranes are composed of a lipid bilayer, which is a double layer of phospholipids. Phospholipids are molecules that have a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail. The hydrophilic heads of the phospholipids face the water on the outside and inside of the cell, while the hydrophobic tails face each other in the middle of the membrane.
Proteins are also found in biological membranes. Proteins can be embedded in the lipid bilayer, or they can be attached to the surface of the membrane. Proteins have many different functions in the cell, including transport, signaling, and cell adhesion.
The ratio of proteins to lipids in biological membranes varies depending on the type of cell. In general, animal cell membranes have a higher percentage of proteins than plant cell membranes.
Here is a brief explanation of each option:
- Option A: 40% proteins and 60% lipids. This is not the correct answer because the percentage of proteins in biological membranes is typically higher than 40%.
- Option B: 50% proteins and 50% lipids. This is not the correct answer because the percentage of proteins in biological membranes is typically higher than 50%.
- Option C: 70% proteins and 30% lipids. This is the correct answer because the percentage of proteins in biological membranes is typically around 70%.
- Option D: 60% proteins and 40% lipids. This is not the correct answer because the percentage of proteins in biological membranes is typically higher than 60%.