The function of nutrition includes all the processes that the cell needs to take the matter and energy it needs to live, grow, replace its damaged structures, divide, and expel waste substances toxic to the cell to the external environment.
Nutrition can be of two types:
- Autotrophic nutrition. Cells can manufacture the organic matter that forms their food, from simple inorganic substances (H2O, CO2 and mineral salts) from an external energy source (the Sun, for example). In photosynthesis, energy from the Sun is captured by a pigment in chloroplasts called chlorophyll.
- Heterotrophic nutrition. Cells cannot synthesize the organic matter that constitutes their food, and they must obtain it from the environment. They have to feed on other living beings, their products or their remains.
The relationship function enables the cell to interact with its environment. It can capture stimuli (light, chemical or mechanical) from the environment and respond to them, such as moving or performing any other type of movement.
Interactive activity: What is the stimulus?.
Interactive activity: How do they move?.
Interactive activity: amoeboid and vibratile or flagellar movement.
The reproduction function is what allows cells to produce two or more offspring similar to them. Cells have the same genetic material as the cell it came from.
Although living beings can have sexual reproduction, the reproduction of cells is asexual, that is, without exchange of genetic material between two parents.
- Reproduction in prokaryotic cells. A simple division by bipartition occurs. The circular DNA of the bacterium is duplicated, forming two exactly the same copies. These DNA molecules are separated, and the prokaryotic cell divides into two halves that will form the two daughter cells, smaller, but genetically identical to the progenitor cell.
- Reproduction in eukaryotic cells. It is a somewhat more complex process that we will see in the next section (cell cycle). It begins with the division of the nucleus by mitosis, into two equal parts. Cytokinesis then occurs, with division of the cytoplasm by bipartition, gemmation or sporulation.
Interactive activity: Cell functions.
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