Cells are the basic building blocks of life. They contain smaller parts, called organelles, which can be roughly compared to the organs of a body. These organelles serve varied purposes within the cell to maintain the health of the cell itself, as well as the health of the larger organism which they make up. Different cells have different duties. A cardiac cell has the job of maintaining a strong, regular heartbeat. A nerve cell must carry electrical and chemical messages. In a plant, a root cell must absorb nutrients, a leaf cell must carry absorb sunlight and make food, a stem cell must make food and support the plant.
Plant cells and animal cells have many organelles that are the same, or at least serve the same purpose, but they have some differences as well, such as general shape, the cell enclosure, the water container, and the pigment cells of the plant that aid in photosynthesis.
The first difference is that a plant cell not only has a cell membrane to control what enters and exits the cell, it also has a cell wall with a rigid, cellulose wall surrounding the cell membrane. The cell wall gives the cell shape and allows the cell to absorb large amounts of water without bursting the less resilient cell membrane that is protected within it. It also protects the cell from losing water to dehydration.
Another major difference is that plant cells have a large central vacuole that takes up as much as 90% of the cell. This vacuole holds the water in the cell. Since plants are largely water (this is why they wilt when they don’t get enough water), this is important. Animal cells, too have vacuoles, but they are more numerous and smaller than in the plant cell.
Plants make their own food through photosynthesis, which requires chlorophyll. That pigment is stored in organelles called chloroplasts within plant cells. Animal cells do not contain these at all.
Overall, animal cells can have many different shapes. For example a nerve cell has a round portion at one end with small projections called dendrites extending from it, and a long body called the axon. A red blood cell is shaped much like a donut without a complete hole in the middle. Muscle cells are very fiberlike and dense and are grouped together tightly. However, most plant cells are shaped much like a rectangle with rounded corners. They tend to have more regular shapes than animal cells because of their rigid cell walls and must stack together to form the plant.
