مصادر الكيمياء موقع لتعليم الكيمياء بصورة مبسطة

aceruloplasminemia or acaeruloplasminaemia a rare autosomal recessive disorder in which plasma ceruloplasmin is severely deficient, characterized by neurological abnormalities and systemic hemosiderosis. Any of at least six mutations in a locus at 3q21-q24 can cause the disease.

خلية A (سابقًا) خلية ألفا  , وهي واحدة من ثلاثة أنواع من الخلايا النسيجية الرئيسية الموجودة في جزر لانغرهانس للبنكرياس ، كما توجد في الغشاء المخاطي للمعدة المفرزة للحمض. تقوم الخلايا بإنتاج وتخزين وإفراز هرمون الجلوكاجون.

المول Mole (منهاج الكيمياء المستوى الأول – الكلية الجامعية بالجموم)   ما هو المـول ؟ هو وحدة أساسيّة في النظام الدولي للوحدات، تستخدم في الكيمياء بشكل كبير،  و هو الوحدة الفعلية لكمية المادة وهو غير الكتلة. و لمعرفة كمية المادة أي عدد مولاتها n لا تتطلب سوى معرفة شيئين فقط الاول هو كتلة المادة بوحدات الجرام m  والثاني الكتلة المولية …

ACC synthase EC 4.4.1.14; systematic name: S-adenosyl-L-methionine methylthioadenosine lyase; an enzyme present in plant tissues that catalyses the pyridoxal phosphate-dependent conversion of Sadenosylmethionine to 1-aminocyclopropane-1-carboxylic acid (ACC) and 5′-methylthioadenosine. It has been cloned from various fruits – zucchini (courgette), tomato, apple – and has 48–97% sequence identity in different plants. Tomato contains several genes for the enzyme that are differentially …

accessory pigment any of the pigments, such as the yellow, red, or purple carotenoids and the red or blue phycobiliproteins in photosynthetic cells. The carotenoids are always present, whereas the phycobiliproteins occur only in algae belonging to the Rhodophyceae, the Cyanophyceae, and the Cryptophyceae. Strictly speaking, chlorophyll b is also an accessory pigment.

ACC oxidase an enzyme present in plant tissues that catalyses the Fe2+– and ascorbate-dependent oxidation of 1-aminocyclopropane-1- carboxylic acid (ACC) to ethylene, CO2, HCN, and H2O. It is a highly unstable monomer (35 kDa) that is inhibited by Co2+. Its activity increases under conditions of stress and at certain developmental stages (e.g. during fruit ripening).

accession number a systematic (computer-readable) number or code that uniquely identifies an entry in a particular database. Accession numbers are assigned when entries are first added to a database and should remain static between updates, providing a reliable means of locating them in subsequent releases. For example, P02699 identifies bovine rhodopsin in the Swiss-Prot database, and IPR000276 identifies the rhodopsin-like …

a.c. calorimetry a technique in which the thermal response of a sample to an oscillating heat signal is measured in the form of a temperature wave propagating through the sample. The technique allows the measurement of the heat capacity of the sample on both cooling and heating and the monitoring of its isothermal time-dependence. It is useful in the study …

acatalasemia or acatalasaemia or Takahara disease a rare, generally benign condition in which erythrocyte catalase activity is less than 1% of normal. It is sometimes associated with ulcerating lesions in the mouth. It is caused by a splice junction mutation in the catalase gene locus at 11p13.

absorption spectrum a spectrum produced when electromagnetic radiation is absorbed by a sample. The frequencies of the radiation absorbed are those able to excite the atoms or molecules of the sample from their ground states to excited states. The frequency, ν, at which a particular absorption line occurs depends on the energy difference, ΔE, between that of a particular ground …