The chemical substances that enter the structure of the cell are essential for life. They provide energy, structure, and information. The most important of these substances are:

* **Water:** Water is the most abundant substance in the cell, making up about 70% of its mass. It is essential for many cellular processes, including transport, metabolism, and signaling.
* **Proteins:** Proteins are the building blocks of cells. They make up enzymes, structural proteins, and transport proteins. Proteins are also involved in cell signaling and gene expression.
* **Lipids:** Lipids are a diverse group of molecules that include fats, oils, and waxes. They are essential for cell structure, energy storage, and signaling.
* **Nucleic acids:** Nucleic acids are the molecules that store genetic information. DNA is the genetic material of all living cells, while RNA is involved in protein synthesis.

I have selected these substances because they are the most important chemical components of cells. They are essential for life and play a role in many cellular processes.

Here are some specific examples of the importance of these substances:

* **Water:** Water is essential for transport. It helps to carry nutrients and waste products into and out of cells.
* **Proteins:** Proteins are essential for structure. They make up the cell’s cytoskeleton, which provides support and shape to the cell.
* **Lipids:** Lipids are essential for energy storage. They are the main component of fat cells, which store energy for later use.
* **Nucleic acids:** Nucleic acids are essential for information storage. DNA stores the genetic information of all living cells, while RNA is involved in protein synthesis.

These are just a few examples of the importance of chemical substances in the structure of cells. Without these substances, life as we know it would not be possible.