Yağlar
Özet
Açlık, tedavi edilmemiş tip I diyabet veya düşük/sıfır karbonhidrat içeriğine sahip yüksek yağlı bir diyet sırasında dolaşıma salınan serbet yağ asitleri karaciğerde ketogenezle keton cisimciklerine dönüşür (asetoasetat, b-hidroksibutirat ve aseton). Çok uzun zincirli yağ asitleri (20 veya daha fazla karbon atomu içerenler) peroksizomal β-oksidasyonla kısa ve orta uzunlukta yağ asitlerine küçültülür. Vücuda enerji vermek dışında metabolik faydası olmayan etil alkolün fazla tüketimi vücut için toksik bir bileşik olan asetaldehitin üretimine neden olur. İnsan hücresi temel yağ asitleri olan linoleik asit ve a-linolenik asit haricinde, asetil-CoA'dan yağ asitleri sentezleyebilir. Trigliseritler (triaçilgliserol), gliserol ve üç yağ asidi molekülünün esterleridir. Kolesterol tüm hücre zarlarının yapısal bir bileşenidir ve akışkanlıklarını düzenler, özel dokularda kolesterol safra asitlerinin, steroid hormonlarının ve D vitamininin öncüsüdür. Hepatik kolesterol havuzuna diyet kolesterolü ve ayrıca karaciğer dışı dokular ve karaciğerin kendisi tarafından de novo sentezlenen kolesterol de dahil olmak üzere birçok kaynaktan kolesterol gelir. Safra asitleri ve safra tuzları, sindirim ve emilim için diyet lipitlerini emülsifiye etmek üzere ince bağırsakta aktif rol oynar. Kolesterol, tüm steroid hormon sınıflarının öncüsüdür: glukokortikoidler (kortizol), mineralokortikoidler (aldosteron) ve seks hormonları (androjenler, östrojenler ve progestinler). Sentez ve salgılanma adrenal kortekste (kortizol, aldosteron ve androjenler), yumurtalıklarda ve plasentada (östrojenler ve progestinler) ve testislerde (testosteron) gerçekleşir. Steroid hormonları, kan yoluyla sentez yerlerinden hedef organlarına taşınır.
During starvation, untreated type I diabetes or a high-fat diet with low/no carbohydrate content, free fatty acids released into the circulation are converted into ketone bodies (acetoacetate, b-hydroxybutyrate and acetone) by ketogenesis in the liver. Very long-chain fatty acids (those containing 20 or more carbon atoms) are reduced to short and medium-length fatty acids by peroxisomal β-oxidation. Excessive consumption of ethyl alcohol, which has no metabolic benefit other than providing energy to the body, causes the production of acetaldehyde, a toxic compound for the body. Human cells can synthesize fatty acids from acetyl-CoA, except for the essential fatty acids linoleic acid and α-linolenic acid. Triglycerides (triacylglycerol) are esters of glycerol and three fatty acid molecules. Cholesterol is a structural component of all cell membranes and regulates their fluidity. In special tissues, cholesterol is a precursor of bile acids, steroid hormones and vitamin D. The hepatic cholesterol pool receives cholesterol from many sources, including dietary cholesterol as well as cholesterol synthesized de novo by extrahepatic tissues and the liver itself. Bile acids and bile salts are active in the small intestine to emulsify dietary lipids for digestion and absorption. Cholesterol is the precursor of all classes of steroid hormones: glucocorticoids (cortisol), mineralocorticoids (aldosterone), and sex hormones (androgens, estrogens, and progestins). Synthesis and secretion occur in the adrenal cortex (cortisol, aldosterone, and androgens), the ovaries and placenta (estrogens and progestins), and the testes (testosterone). Steroid hormones are transported from their sites of synthesis to their target organs by the blood.
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