A cell is the basic unit of all life. All living things are made up of cells humans, dogs, plants are made up of cells. Some plants animals and animals are made up of only one cell while others are made up of many cells. Most cells are so small that man can only see them under a microscope. It takes more than a million cells to make up one square inch of your skin. Cells may be shaped like cubes, coils, boxes, snowflakes, corkscrews, rods, saucers, rectangles, or blobs of jelly. Cells vary widely in size, just as they do in shape. Bacteria cells are among the smallest fo all cells.
THE NUCLEUS.
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The nucleus is the control center that directs the cell's activities. It is a round body near the center of the cell. A nuclear membrane surrounds the nucleus and separates it from the cytoplasm. The nucleus contains two important structures: the chromatin and nucleoli.
Chromatin consists chiefly of two substances DNA. DNA controls every living things characteristics from parents to offspring. DNA makes a dog give birth to a dog instead of a moose and makes a spruce tree differ from a human. It determines physical characteristics such as eye color and the shape of your body and literally thousands of other characteristics.
THE CYTOPLASM.
The cytoplasm is all the cell except the nucleus. Proteins are made in the cytoplasm, and here most of the cell's life activities take place. The cytoplasm is mostly water. Many tiny structures called organelles are submerged in this water in this water. Each has a particular job to do. Thes organelles are called mitochondria, lysosomes, the endoplamic reticulum, centrioles, and golgi bodies. The mitochondria are th power producers of the cell. Lysosomes contain enzymes that can break down most of the cell's structures and they dissolve cells after they die.
