It seems like you're referring to the structure of a phospholipid bilayer, which is a fundamental component of the cell membrane in biological cells. Here's a step-by-step explanation:

1. The phospholipid bilayer is composed of two layers of phospholipids. Each phospholipid molecule contains a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail.

2. The hydrophilic heads are attracted to water, so they position themselves towards the aqueous environments both inside and outside of the cell.

3. The hydrophobic tails, on the other hand, are repelled by water. They position themselves away from the aqueous environments, towards the center of the bilayer.

4. This arrangement results in a 'sandwich' structure, with the hydrophilic heads forming the outer surfaces of the membrane, and the hydrophobic tails forming the inner part of the membrane.

5. This structure allows the cell membrane to be selectively permeable, controlling the movement of substances in and out of the cell. The hydrophobic core of the membrane acts as a barrier to most water-soluble (hydrophilic) substances.

6. However, nonpolar, hydrophobic molecules can dissolve in the hydrophobic core and pass through the membrane with ease. This includes gases like oxygen and carbon dioxide, and small, nonpolar molecules like steroids.

7. This is the basic structure and function of the phospholipid bilayer in the cell membrane.

Question

It seems like you're referring to the structure of a phospholipid bilayer, which is a fundamental component of the cell membrane in biological cells. Here's a step-by-step explanation:

1. The phospholipid bilayer is composed of two layers of phospholipids. Each phospholipid molecule contains a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail.

2. The hydrophilic heads are attracted to water, so they position themselves towards the aqueous environments both inside and outside of the cell.

3. The hydrophobic tails, on the other hand, are repelled by water. They position themselves away from the aqueous environments, towards the center of the bilayer.

4. This arrangement results in a 'sandwich' structure, with the hydrophilic heads forming the outer surfaces of the membrane, and the hydrophobic tails forming the inner part of the membrane.

5. This structure allows the cell membrane to be selectively permeable, controlling the movement of substances in and out of the cell. The hydrophobic core of the membrane acts as a barrier to most water-soluble (hydrophilic) substances.

6. However, nonpolar, hydrophobic molecules can dissolve in the hydrophobic core and pass through the membrane with ease. This includes gases like oxygen and carbon dioxide, and small, nonpolar molecules like steroids.

7. This is the basic structure and function of the phospholipid bilayer in the cell membrane.

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