Orientation in Biological Definition

Beta sheet

... protein that are arranged adjacently and in parallel, but with alternating orientation such that hydrogen bonds can form between the two strands. The amino ... a β sheet, when traced along the backbone, take a hairpin turn in orientation (direction), sometimes through one or more prolines . See also : ...

Activation energy

... energy needed for a specific chemical reaction to occur. For a reaction to occur between two colliding molecules they must collide in the correct orientation and possess a certain minimum amount of energy. As the molecules approach their electron clouds repel. This requires energy - activation energy - and ...

Cladistics

... and analysis of morphology , treelike relationship-diagrams called "cladograms" are drawn up to show different possibilities. A vertical orientation yields a cladogram reminiscent of a tree . In a cladogram, all organisms lie at the leaves, and each inner node is ideally binary (two-way). The ...

DNA

... in living cells. Direction of DNA strands The asymmetric shape and linkage of nucleotides means that a DNA strand always has a discernible orientation or directionality. Because of this directionality, close inspection of a double helix reveals that nucleotides are heading one way along one strand ...

Enhancer

... several hundreds of thousands base pairs upstream or downstream of the start site. Enhancers can also be found inside introns . An enhancer's orientation may even be reversed without affecting its function. Furthermore, an enhancer may be excised and inserted elsewhere in the chromosome, and still ...

Enzyme

... (in Greek en = in and zyme = blend) is a protein , or protein complex , that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. Like any catalyst, enzymes work by lowering the activation energy of a reaction, thus allowing the reaction to ...

Glucose

... itself may form in two additionally different ways, yielding α (alpha) glucose and β (beta) glucose. Structurally, they differ in the orientation of the hydroxyl group linked to the first carbon in the ring. The α form has the hydroxyl group "below" the hydrogen (as the molecule is ...

Meiosis

... chromosomes from the diploid to the haploid condition separates alleles so that each gamete carries a sole allele for a gene locus. In addition, the orientation of the metaphase I/II equatorial lining-up is random, resulting in new allelic recombinationis. Independent assortment forms the basis of Mendel 's ...

Magnetic resonance imaging

... simulation, a patient is placed in specific, reproduceable, body position and scanned. The MRI system then computes the precise location, shape and orientation of the tumor mass, correcting for any spatial distortion inherent in the system. The patient is then marked or tatooed with points which, when ...

Signal transduction

... DNA sequences that match the receptor are usually hexameric repeats, either normal, inverted or everted. The sequences are quite similar, but their orientation and distance are the parameters by which the DNA-binding domains of the receptors can tell them apart. Steroid receptors Steroid ...

Tubulin

... from dimers of α- and β-tubulin. Each of these subunits has three domains . γ-tubulin is important in the nucleation and polar orientation of microtubule. Tubulin binds GTP and assembles onto the (+) ends of microtubules in the GTP-bound state. Once assembled into microtubules, it ...

Vestibular system

... The vestibular system , or balance system , is the sensory system that provides the dominant input about our movement and orientation in space. Together with the cochlea, the auditory organ, it is situated in the vestibulum in the inner ear (Figure 1). As our movements consist ...