Atoms come together to form biomolecules and these group together to form higher units that already have life, which are cells. Cells, like all living beings, carry out vital functions in order to keep alive the individual of which they are a part (nutrition and relationship) and to perpetuate it (reproduction).
The cell is the smallest structure that can be considered a living being.
The cell is the structural and functional unit of living beings.
- The cell is the structural unit of living things because all living things are made up of cells, although not all living things have the same number of cells. According to the number of cells, there are two types of living beings:
- The cell is the functional unit of living beings because it is the smallest structure that is capable of performing the three vital functions:
The discoveries about cells were made as the technique progressed, allowing the manufacture of new microscopes that facilitated their observation.
The cell theory (Schleiden and Schwann, 1839) postulated that:
- Every living thing is made up of one or many cells.
- The cell is the smallest structure that fulfills all vital functions (nutrition, relationship and reproduction).
- Every cell comes from another cell by division of the same.
Basic structure of cells
All cells are made up of:
- The plasma membrane is a layer that surrounds the cell. It separates the interior from the cell exterior and is responsible for protecting the cell and regulating the passage of substances between the exterior and the interior of the cell.
- The cytoplasm is the part of the cell that is surrounded by the membrane. It is made up of an aqueous medium (cytosol) in which cell organelles float. Organelles are structures responsible for carrying out various functions. In the cytosol are the substances necessary for the life of the cell.
- Genetic material (DNA) is a substance that contains hereditary information and controls the functioning of the cell.