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Diagram of the nucleus showing the ribosome-studded outer nuclear membrane, nuclear pores, DNA (complexed as chromatin), and the nucleolus. The nucleus contains nearly all of the cell's DNA, surrounded by a network of fibrous intermediate filaments called the nuclear matrix, and is enveloped in a double membrane called the nuclear envelope.
Unlike eukaryotes, bacterial membranes (with some exceptions e.g. Mycoplasma and methanotrophs) generally do not contain sterols. However, many microbes do contain structurally related compounds called hopanoids which likely fulfill the same function. Unlike eukaryotes, bacteria can have a wide variety of fatty acids within their
A diagram of an animal cell. Eukaryotic cells are composed of the following organelles: Nucleus: The nucleus of the cell functions as the genome and genetic information storage for the cell, containing all the DNA organized in the form of chromosomes.
Each human cell contains around two metres of DNA, which must be tightly folded to fit inside the cell nucleus. However, in order for the cell to function, proteins must be able to access the sequence information contained within the DNA, in spite of its tightly-packed nature. Hence, the cell has a number of mechanisms in place to control how ...
A study of the comparative genomics, evolution and origins of the nuclear membrane led to the proposal that the nucleus emerged in the primitive eukaryotic ancestor (the “prekaryote”), and was triggered by the archaeo-bacterial symbiosis. [24] Several ideas have been proposed for the evolutionary origin of the nuclear membrane. [25]
Most circular bacterial chromosomes are replicated bidirectionally, starting at one point of origin and replicating in two directions away from the origin. This results in semiconservative replication, in which each new identical DNA molecule contains one template strand from the original molecule, shown as the solid lines, and one new strand ...
The cytoplasm contains the cytoskeleton, a network of protein filaments found in all cells, while the nucleoplasm is believed to contain the nuclear matrix, a hypothetically analogous network of filaments that organizes the organelles and genetic information within the nucleus. While the structure and function of the cytoskeleton have been well ...
Bacteria do not have a membrane-bound nucleus, and their genetic material is typically a single circular bacterial chromosome of DNA located in the cytoplasm in an irregularly shaped body called the nucleoid. [68]