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Prokaryotic cells have no membranous organelles and their activity takes place in the membrane. The way they receive nutrients can be autotrophic and heterotrophic.
Prokaryotic organisms were the first living beings to appear on Earth, some 3.5 billion years ago. Their internal structure was very simple, with DNA scattered in the cytoplasm, in a region called the nucleoid that was not separated from the rest of the cytoplasm.
- This is where DNA is found.
- One of the distinctive elements of a prokaryotic cell is that it lacks a nucleus. Instead it has a nucleoid, an irregular region located inside the cells.
Nucleoid: DNA is made up of a circular DNA molecule. It’s dispersed in the cytoplasm, in an area called the nucleoid.
- Organelles in the cytoplasm, responsible for protein synthesis.
Ribosomes: These are the only organelles present in prokaryotic cells.
- In some places, the plasma membrane folds inwards forming mesosomes, structures involved in cellular respiration and reproduction.
- Regulates the entry and exit of substances into the cell.
Plasma membrane: As well as this membrane, the structure of the prokaryotic cell contains: Bacterial capsule: Some prokaryotic cells may have a thick, rigid capsule that wraps around the outside. Cell wall: A strong, rigid envelope that shapes the cell between the plasma membrane and the bacterial capsule (if any). Cytoplasm: Internal space delimited by the plasma membrane. Flagella: They are extensions of the cytoplasm that allow movement in some bacteria. Fimbriae and pili: They are short and numerous filaments that have various functions, such as fixing the bacteria to the substratum or exchanging molecules with other cells or with the outside.