Internal and external hydrogen bonds<span> stabilize the </span>DNA<span> molecule. The two strands of</span>DNA<span> stay together by H </span>bonds<span> that occur between complementary nucleotide base pairs. Two </span>hydrogen bonds<span> occur between the adenosine and the thymine base pairs, and between the cytosine and the guanine there are three.</span>
Answer:
the primary function of the plasma membrane is to protect the cell form its surroundings. composed of a phospholipid bilayer with embeded with proteins the plasma membrane is selectively permeable to ions and organic molecules and regulates the movement of substances in and out of cells.
Explanation:
Explanation:
The Chandra X-ray observatory or CXC for its acronym in English, is an artificial satellite launched by NASA on July 23, 1999. It was named in honor of Indian physicist Subrahmanyan Chandrasekhar, one of the founders of astrophysics, who determined the boundary mass at which white dwarfs become a neutron star. In addition, Chandra means "moon" in Sanskrit.
The Chandra Observatory is the third of the Great Observatories of NASA. The first was the Hubble Space Telescope, the second was the Gamma Compton Ray Observatory, launched in 1991 and already disintegrated, and the last was the Spitzer Space Telescope. Before launching the Chandra Observatory was known as AXAF by the acronym in English of Advanced X-ray Astronomical Facility.
As the Earth's atmosphere absorbs most X-rays, conventional telescopes cannot detect them and a space telescope is necessary for their study.
In 1976 Riccardo Giacconi and Harvey Tananbaum proposed to NASA the idea of the Chandra Observatory, beginning preliminary work at the Marshall Space Flight Center. Meanwhile, in 1978, NASA launched the first X-ray space telescope, the Einstein (HEAO-2).
Despite this, work on the Chandra project continued during the 1980s and 1990s, but in 1992 the ship was redesigned to reduce costs. Four of the twenty mirrors that the observatory was going to dispose of were removed, and an elliptical orbit with which it would reach a third of the distance to the moon was calculated. This eliminated the possibility of being repaired by the space shuttle, but placed the observatory outside the influence of the earth's radiation belts most of its orbit.