substance

X-ray crystallography

...uclei . The material and molecular structure of a substance can often be inferred by quantitative study of this pattern. It is widely used in chemistry and biochemistry to determine the structures of an immense variety of molecules, including inorganic compounds, DNA and proteins . Contents show...

Thermoregulation

...sthose of oxidationundergone not by any particular substance or in any one place, but by the tissues at large. Wherever destructive metabolism ( catabolism ) is going on, heat is being set free. When a muscle does work it also gives rise to heat, and if this is estimated it can be shown that the muscles alone ...

Stem cell

...neered to convert a separately injected non-toxic substance into a cancer-killing agent. Within days the adul... migrated into the cancerous area and the injected substance was able to reduce tumor mass by 80 percent. Spinal cord Embryonic stem cells switched to neur...

Blood type

...t, antigen B on the cell and produce antibodies to substance A in their serum. Type AB people have red blood...nd B, and do not produce antibodies against either substance in their serum. Therefore, a person with type AB blood can safely receive any ABO type blood and is ...

Redox

...can gain one or two extra electrons by oxidizing a substance ( O 2 , O 3 , F 2 , Cl 2 , Br 2 ) Substances that have the ability to reduce other substances are said to be reductive and are known as reductive agents / reductants or reducers . Put in another way, the reductant transfers electrons...

Protein

...;ειοξ, parce quil parat tre la substance primitive ou principale de la nutrition animale.&r...ecause it appears to be the primitive or principle substance of animal nutrition." Investigation of proteins and their properties had been going on since ab...

Photosynthesis

...e growing plant must come from the water, the only substance he added to the potted plant. Joseph Priestley , a chemist and minister, discovered that when he isolated a volume of air under an inverted jar, and burned a candle in it, the candle would burn out very quickly, much before it ran out of wax. He fu...

Redox

...can gain one or two extra electrons by oxidizing a substance ( O 2 , O 3 , F 2 , Cl 2 , Br 2 ) Substances that have the ability to reduce other substances are said to be reductive and are known as reductive agents / reductants or reducers . Put in another way, the reductant transfers electrons...

Origin of life

...ayers of dark material, thought to be a tar -like substance composed of complex organic material formed from simple carbon compounds after reactions initiated mostly by irradiation by ultraviolet light. It is supposed that a rain of cometary material on the early Earth could have brought significant quantit...

Operon

...is, the "operator") is turned on unless a specific substance is bound to the operator. This substance is therefore called a repressor. In summary: The "operator" is a DNA binding site for a represso...

Neurotransmitter

...inistered, it must mimic the endogenously released substance A biochemical mechanism for inactivation must ...rokinin B neuropeptide A neuropeptide gamma substance P Biogenic amines : acetylcholine ( ACh ) Other: nitric oxide ( NO ) carbon mo...

Neuron

...es will show numerous microscopic clumps of Nissl substance (named after German psychiatrist and neuropatholo...ssociated ribosomes . The prominence of the Nissl substance can be explained by the fact that nerve cells are metabolically very active, and hence are involved ...

Monoclonal antibody

...nal antibodies Production If a foreign substance (an antigen ) is injected into a vertebrate suc...lications Once monoclonal antibodies for a given substance have been produced, they can be used to detect for the presence and quantity of this substance, for ...

Malaria

... annua ), containing the compound artemisinin , a substance unrelated to the quinine derivatives, offer some future promise. Prospects of disease control Vaccines for malaria are under development, with no completely effective vaccine yet available (as of November 2004 ). A team backed by the Gates Fou...

Macromolecule

...cule and the term polymer is used as to denote a substance composed of macromolecules. Polymer may also be employed unambiguously as an adjective, according to accepted usage, e.g. polymer blend, polymer molecule. [2]...

Lipid

...e "hydrophobic effect." When dissolving a nonpolar substance in a polar environment, the polar molecules (i.e. water in an aqueous solution) become more ordered around the dissolved nonpolar substance, since the polar molecules cannot form hydrogen bonds to the nonpolar molecule. Therefore, in an aqueous env...

Photosynthesis

...e growing plant must come from the water, the only substance he added to the potted plant. Joseph Priestley , a chemist and minister, discovered that when he isolated a volume of air under an inverted jar, and burned a candle in it, the candle would burn out very quickly, much before it ran out of wax. He fu...

Gene regulatory network

...d; for inputs and outputs, "on" corresponds to the substance being present. Time is viewed as proceeding in discrete steps. At each step, the new state of a node is a boolean function of the prior states of the nodes with arrows pointing towards it. The validity of the model can be tested by comparing si...

Fehling's solution

...used to detect aldehyde functional groups . The substance to be tested is heated together with Fehling's solution; a red precipitate indicates the presence of aldehydes or aldehyde groups. An example for its use is to screen for glucose in urine , thus detecting diabetes . It was developed by German c...

Eye

...ly spherical, filled with a transparent gel-like substance called the vitreous humour , with a focusing lens and often a muscle called the iris that controls how much light enters. Although they are quite similar in function and appearance once fully developed, vertebrate eyes grow outward from brain c...

Endodermis

...ial walls which are made of suberin mainly, a waxy substance which prevents water from flowing back into the soil. Water is thus forced toward the center of the root, into the xylem , where it is then transported into the rest of the plant....

Drug

A drug is any substance that can be used to treat an illness , to relieve...may be. Depending on the definition used, the same substance may even be considered both a food and a drug at the same time. The term "medication" is frequently ...

DNA

...t led to the identification and naming of DNA as a substance distinct from RNA. Friedrich Miescher ( 1844 - 1895 ) discovered a substance he called "nuclein" in 1869 . Somewhat later, he isolated a pure sample of the material now known a...

Digestion

... a substance, in order to chemically convert the substance into nutrients . Digestion occurs at the multicellular , cellular , and sub-cellular levels. Digestion usually involves mechanical manipulation and chemical action. In most vertebrates , digestion is a multi-stage process in the digestive syst...

Diabetes mellitus

...roduced by the pancreas - he proposed calling this substance insulin. The endocrine role of the pancreas in metabolism, and indeed the existence of insulin, was not fully clarified until 1921 , when Sir Frederick Grant Banting and Charles Herbert Best repeated the work of Von Mering and Minkowski but wen...

Chromatography

...The retention is a measure of the speed at which a substance moves in a chromatographic system. In continuous d...t the paper and may form interactions with it. Any substance that will react with (and thus bond to) the paper cannot be measured using this technique. The paper...

Chromatin

Chromatin is the substance of a chromosome and consists of a complex of DNA and protein in eukaryotic cells . It can be made visible by staining (thus the name which literaly means coloured material). The nucleic acids are generally in the form of double-stranded D...

Antigen

...are several kinds of antigens: Immunogen - Any substance that provokes an immune response (provokes immunit...form is changed. Allergen - An allergen is any substance that causes an allergic reaction . It can be eaten, inhaled, injected or comes into contact with sk...

Antibiotic

... that stopped bacterial growth. He knew that this substance might have enormous utility to medicine. Although he was unable to purify the compound (the beta-lactam ring in the penicillin molecule was not stable under the purification methods he tried), he reported it in the scientific literature. Since the ...

Alexander Fleming

...ash; March 11 , 1955 ) discovered the antibiotic substance lysozyme and isolated the antibiotic substance penicillin from the fungus Penicillium notatum . Biography Fleming was born on a farm at ...

Alcohol

... , together with the art of distillation and the substance itself, around the 12th century by various European authors who translated and popularized the discoveries of Islamic alchemists . A popular theory, found in many dictionaries, is that it comes from الكحل = ALKHL...

Active transport

... energy is directly coupled to movement of desired substance across a membrane, independent of any other species. Secondary transport concerns the diffusion of one species across a membrane to drive the transport of another. Primary Primary active transport directly uses energy to transport molecules acr...

Activation energy

... both positions lie below the transition state). A substance that modifies the transition state to lower the activation energy is termed a catalyst ; a biological catalyst is termed an enzyme . Fig 1. The enthalpy profile of a reaction between two hydrogen peroxide molecules to form water and ...