Introducing the Cell

Living things on earth share certain similarities and differences. One basic common structure of both plants and animals is their make-up of _____, which are the basic building blocks of life and have distinct parts within them.

Both plants and animals are made up of a variety of cells. In order to see them, scientists use special tools. One of the most powerful instruments to view cells is the _____. This device uses magnets to focus beams of electrons on the subject.

Scientists learn how cells function by examining the very tiny parts of the inside of the cell. The _____ surrounds the outside of an animal cell. This thin structure allows food, water and oxygen to pass into the cell and waste products to pass out of it.

Within the cell there are many different structures called organelles. This word means "little organs." One of these organelles is the _____, which is the control center of the cell. This organelle has a membrane which has pores, or holes, in it to allow certain molecules to enter and leave it.

The nucleus of a cell has various parts within it to assist it as the control center of the cell. Inside the nucleus are _____, which contain the cell's genetic information. These structures determine those physical characteristics that will be passed down to the offspring.

Plant cells have cell structures and functions different from animal cells. For example, a plant cell has a _____ which is not found in animal cells. This material surrounds the cell membrane and protects it as well. This structure also gives the cell a definite shape.

Plant cells have other specific parts also that help it to grow and thrive. Plant cells contain _____ which are spaces, or sacs, that hold liquids. These structures are often filled with water which helps keep a plant cell rigid. When these structures lose their water, the plant wilts or dries out.

In plants, the important food-making structures are the chloroplasts. They make it possible for _____ to take place. Inside the chloroplasts the energy of sunlight is used to convert carbon dioxide and water into glucose, a kind of sugar. Oxygen, which we breathe, is also given off.

When we look at animal cells we see that they also have cells that perform specific functions. The _____ consist of several layers of skin cells that fit closely together. These layers of cells protect the body from harmful bacteria and are constantly worn away and replaced.

Unlike plants, animals are in motion and therefore must have specific cells to help them to move. The _____ are long and fiber-like. Thousands of these cells contract and expand together, making it possible to move arms and legs. The cells of plants and animals are truly unique