Like all living things, plants are made of cells, the smallest and simplest unit of life. While plant cells share some characteristics with the cells found in the human body, such as a plasma layer, they are also different in many important ways. All plant cells share the same key components and characteristics, even though like humans, plants have many different kinds of cells specialized at carrying out different functions.
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All plant cells are eukaryotic. This means that their DNA, or genetic material, is contained within the nucleus of cells. The other type of cells, called prokaryotic, do not have a nucleus. Eukaryotic cells are about 10 times the size of their counterparts, and the DNA in the nucleus is organized into chromosomes.
Plant cells contain a variety of different organelles, or microscopic organs, each performing different functions. Some organelles found in plant cells include the ribosomes, mitochondria and chloroplasts. Chloroplasts are where photosynthesis, the process by which sunlight is converted into energy, takes place. The ribosomes are responsible for the synthesis of protein. Mitochondria convert energy from glucose into adenosine triphosphate, which is necessary for normal cell function.
In animals, including humans, the cells' exteriors are a plasma membrane. Plants too have this membrane, but it's not the outermost shell of a cell. On top of the membranes, plant cells have rigid walls made of cellulose. The wall provides structure and support for the cell and also bonds with the walls of other cells, creating a plant's structure.
Vaculoes are large structures within plant cells. They are contained by a membrane and filled with fluid. Most cells have just one vacuole, but it takes up a large portion of the cell. Its purpose is to help the cell maintain its shape.