Inside of a Cell

Suppose for a moment you could shrink as small as one of the millions of tiny glucose molecules that make up a sugar crystal. At this size you can easily enter a cell and take a look around.

To get inside the cell, you first must get through the cell membrane. The cell membrane is the covering of teh cell and is made of three layers, giving it the appearance of a "sandwich." The cell membrane serves as a fence around the cell. It controls what enters and exits the cell by opening and closing tiny passageways through the membrane. You enter the cell through one of these tiny pores.

Inside the cell you are immediately surrounded by a jelly-like substance called cytoplasm. This material fills most of the cell and acts as a factory. Located at various places throughout the cytoplasm are organelles, "machines" that carry out particular jobs.

Looking around, you see many unusual structures and a variety of activities taking place. One type of organelle you see looks like long French rolls. They are the mitochondria, the powerhouse of the cell. Mitochondria are surrounded by a double membrane. The inner membrane folds inward many times to form the cristae, which fill most of the inner space. This folded membrane is covered with enzymes that release energy from food. The energy produced by the mitochondria powers all cell activities.

As you stand in the cell, you see in front of a series of flattened channels running throughout the cytoplasm. These channels, called the endoplasmic reticulum, link the rest of the cell with the nucleus, or control center of the cell. In addition, the surface of the endoplasmic reticulum provides an area for reactions to occur and allows for movement of materials throughout the cell.

The surface of the endoplasmic reticulum is studded with thousands of tiny beadlike ribosomes. Other ribosomes float freely throughout the cytoplasm. Regardless of where they are, ribosomes, under the direction of the RNA, combine various amino acids to form proteins. These proteins, in turn, are used a building blocks of the cell.

As you continue to move through the cytoplasm, you see an organelle that looks like a stack of pancakes. This is a Golgi body, which stores fatty substances and helps to manufacture and package hormones.

Ahead you find a number of smaller organelles scattered throughout the cell. Some of these, the vacuoles, appear to be hollow. Vacuoles capture and remove the cell's waste products and are sometimes called the "garbage cans" of the cell. Vacuoles are most common in animal cells.

Farther ahead you see other small organelles, called plastids. These structures act as storage centers for cell products and also as manufacturing centers that produce products, such as carbohydrates, needed by the cell. Plastids are most common in plant cells. One special plastid, called the chloroplast, contains the green pigment chlorophyll and manufactures sugar during photosynthesis.

Nearby are several ball-shaped lysosomes that contain digestive enzymes. They are important in protecting the cell from bacteria. They also help to break down and recycle the parts of the cell when it dies.

As you turn to enter the nucleus, you look to the right and see two centrioles, small barrellike structures positioned at right angles to each other. Most cells have these structures, which help guide the chromosomes apart when the cell divides.