The cell is the basic and indispensable unit present in every living being . It is the smallest living element. The three vital functions of every organism (nutrition, reproduction, interaction) are carried out by all the cells that compose it.
According to their structure, cells can be:
- Eukaryotic cells. They have a defined cell nucleus, covered by a membrane. Inside this membrane are the chromosomes that store the organism’s genetic information. All organisms in the animal kingdom , plant kingdom , fungi , and protist kingdom are made up of eukaryotic cells. For example:the protist plasmodium, the animal cells present in a lobster, the plant cells present in a jacaranda tree.
- Prokaryotic cells. They lack a defined nucleus and a nuclear membrane. Their genetic material is dispersed throughout the cytoplasm, loosely contained in an area called the nucleoid. Bacteria and archaea are the two types of organisms with prokaryotic cells. For example:methanogenic archaea or pseudomonas bacteria.
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Characteristics of eukaryotic cells
- They comprise kingdoms of multicellular beings(made up of several cells) and unicellular beings (made up of a single cell). The cells of each type vary in structure and characteristics. They are much larger than prokaryotic cells.
- They are aerobic, they need oxygen to live.
- They reproduce through mitosis (two genetically identical daughter cells originate from a progenitor cell) and meiosis (four haploid and genetically different cells arise from a diploid progenitor cell).
- They have organelles, structures within the cytoplasm, that perform various functions. For example, in a plant cell, the chloroplast organelle performs the function of photosynthesis. Not all cells have all the organelles.
- They have ribosomes (organelles that synthesize proteins) that are more complex than those of prokaryotic cells.
- Plant cells have cell walls composed of cellulose. Animal cells do not have cell walls.
Characteristics of prokaryotic cells
- They are found only in unicellular organisms. They have a smaller structure and are less complex than eukaryotic cells.
- The genetic material is dispersed in the cytoplasm, in an irregular area called the nucleoid.
- They can be aerobic or anaerobic (they do not need oxygen to live).
- They reproduce asexuallyor parasexually.
- Nutrition can be autotrophic(photosynthesis or chemosynthesis) or heterotrophic (they depend on autotrophs to obtain their food)
- They have cytoplasm, plasma membrane, cell wall, nucleoid and ribosomes.
Examples of eukaryotic cells
- Neuron
- Euglena
- Amoeba
- Red blood cell
- Paramecium
Examples of prokaryotic cells
- Eubacteria
- Spirochetes
- Mycoplasmas
- Blue-green algae
- Methanogens