A new era of spaceflight? Promising advances in rocket propulsion

The US Defense Advanced Research Projects Agency (Darpa) has recently commissioned three private companies, Blue Origin, Lockheed Martin and General Atomics, to develop nuclear fission thermal rockets for use in lunar orbit.

Mammoth moves: frozen cells come to life, but only just

A team of scientists in Japan has successfully coaxed activity from 28,000-year-old cells from a frozen mammoth implanted into mouse cells, but the woolly mammal is unlikely to be walking among us soon.

Bacteria can grow under extreme gravity: study

(PhysOrg.com) -- A new study in the Proceedings of the National Academy of Sciences shows that bacteria is capable of growing under gravity more than 400,000 times that of Earth and gives evidence that the theory of panspermia ...

Scientists find 'man's remotest relative' in lake sludge

After two decades of examining a microscopic algae-eater that lives in a lake in Norway, scientists on Thursday declared it to be one of the world's oldest living organisms and man's remotest relative.

Cells eat themselves into shape

The process cells use to 'swallow' up nutrients, hormones and other signals from their environment – called endocytosis – can play a crucial role in shaping the cells themselves, scientists at the European Molecular Biology ...

Gravity plays a role in keeping cells small

(Phys.org) —The effects of gravity are relevant when building houses or flying airplanes, but biologists have generally accepted that the average cell is too small for gravity to play a role in how it is built or behaves. ...

Searching for fractals may help cancer cell testing

Scientists have long known that healthy cells looked and behaved differently from cancer cells. For instance, the nuclei of healthy cells -- the inner part of the cells where the chromosomes are stored -- tend to have a rounder ...

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Cell nucleus

In cell biology, the nucleus (pl. nuclei; from Latin nucleus or nuculeus, or kernel), also sometimes referred to as the "control center", is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these chromosomes are the cell's nuclear genome. The function of the nucleus is to maintain the integrity of these genes and to control the activities of the cell by regulating gene expression--the nucleus is therefore the control center of the cell.

The main structures making up the nucleus are the nuclear envelope, a double membrane that encloses the entire organelle and separates its contents from the cellular cytoplasm, and the nuclear lamina, a meshwork within the nucleus that adds mechanical support, much like the cytoskeleton supports the cell as a whole. Because the nuclear membrane is impermeable to most molecules, nuclear pores are required to allow movement of molecules across the envelope. These pores cross both of the membranes, providing a channel that allows free movement of small molecules and ions. The movement of larger molecules such as proteins is carefully controlled, and requires active transport regulated by carrier proteins. Nuclear transport is crucial to cell function, as movement through the pores is required for both gene expression and chromosomal maintenance.

Although the interior of the nucleus does not contain any membrane-bound subcompartments, its contents are not uniform, and a number of subnuclear bodies exist, made up of unique proteins, RNA molecules, and particular parts of the chromosomes. The best known of these is the nucleolus, which is mainly involved in the assembly of ribosomes. After being produced in the nucleolus, ribosomes are exported to the cytoplasm where they translate mRNA.

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