Chapter 12, Problem 1P

Interpretation Introduction

Interpretation:

The number of phospholipid molecules in 1µm² of the bilayer membrane needs to be calculated if phospholipid molecule occupies 70 Ų of surface area.

Concept introduction:

Lipids are fatty molecules that occupy 50% of the mass of the cell membrane. Most of the membrane lipids are phospholipids.

Answer to Problem 1P

There are $2.86\times {10}^6$ phospholipid molecules in 1µm²of the bilayer membrane.

Explanation of Solution

Lipid bilayers are two-dimensional fluids which are a universal basis of the cell membrane.

Membrane lipids and proteins move along the membrane.

Lateral diffusion for the phospholipids is very rapid.

Phospholipid moves by 1m² in one sec=molecule diffuses by 2m in one sec.

Molecule travels from one end of the bacterial cell to another in one sec.

Human red blood cells can be passed in 12 sec.

Each leaflet of the bilayer contains $1.43\times {10}^6$ molecules.

There are two leaflets in the bilayer membrane.

Thus, in the bilayer membrane, the number of molecules are:

  = $2\times 1.43\times {10}^6$

  = $2.86\times {10}^6$

Hence, there are $2.86\times {10}^6$ molecules in the 1µm² of the bilayer membrane.

Conclusion

The phospholipid in two layers called a phospholipid bilayer. Each leaflet of the membrane has $1.43\times {10}^6$ molecule hence, the bilayer membrane consists of $2.86\times {10}^6$ molecules.