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Up-regulation is a process which occurs within a cell triggered by a signal (originating internal or external to the cell), which results in increased expression of one or more genes and as a result the proteins encoded by those genes. Conversely, down-regulation is a process resulting in decreased gene and corresponding protein expression.
Prokaryotes have fewer organelles than eukaryotes. Both have plasma membranes and ribosomes (structures that synthesize proteins [clarification needed] and float free in cytoplasm). Two unique characteristics of prokaryotes are fimbriae (finger-like projections on the surface of a cell) and flagella (threadlike structures that aid movement). [2]
The metabolism of prokaryotes is far more varied than that of eukaryotes, leading to many highly distinct prokaryotic types. For example, in addition to using photosynthesis or organic compounds for energy, as eukaryotes do, marine prokaryotes may obtain energy from inorganic compounds such as hydrogen sulfide.
In prokaryotic cells ATP synthase lies across the plasma membrane, while in eukaryotic cells it lies across the inner mitochondrial membrane. Organisms capable of photosynthesis also have ATP synthase across the thylakoid membrane , which in plants is located in the chloroplast and in cyanobacteria is located in the cytoplasm .
The post-glycolytic reactions take place in the mitochondria in eukaryotic cells, and in the cytoplasm in prokaryotic cells. [6] Although plants are net consumers of carbon dioxide and producers of oxygen via photosynthesis, plant respiration accounts for about half of the CO 2 generated annually by terrestrial ecosystems. [7] [8]: 87
In biology, cell signaling (cell signalling in British English) is the process by which a cell interacts with itself, other cells, and the environment. Cell signaling is a fundamental property of all cellular life in prokaryotes and eukaryotes. Typically, the signaling process involves three components: the signal, the receptor, and the effector.
Many proteins are destined for other parts of the cell than the cytosol and a wide range of signalling sequences or (signal peptides) are used to direct proteins to where they are supposed to be. [38] [39] In prokaryotes this is normally a simple process due to limited compartmentalisation of the cell. [40]
Prokaryotes are able to subsist by allowing materials to enter the cell via simple diffusion. Intracellular transport is more specialized than diffusion; it is a multifaceted process which utilizes transport vesicles. Transport vesicles are small structures within the cell consisting of a fluid enclosed by a lipid bilayer that hold cargo. These ...