#Biochemistery
#Carbohydrate_metabolism
#بوست_رقم (16)
ح نبدأ في ال
monosaccharide metabolism
والليلة ان شاء الله ح نبدأ وناخد Galactose metabolism
ودي النقاط اللي ح نتناولها:
📌 Importance of galactose.
📌 Conversion of galactose into glucose.
📌 Conversion of glucose into galactose.
📌 Galactosemia.
يلا بسم الله نبدأ 👋
نبدأ بمقدمة ومعلومات بسيطة كدا
ال galactose دا بجينا من وين؟
From hydrolysis of the lactose in the intestine by lactase enzyme.
🍁 Galactose absorption is faster than Glucose.
🍁 Galactose reaches liver by portal blood where it is readily converted to glucose.
يعني بمجرد ما يصل ال galactose لل liver ح يتحول لي ل glucose.
🍁 This property is used as a test of liver function called galactose tolerance test.
ف ال test دا مهم عشان نعرف الكبد قائمة بوظائفها ولالا.
🔥 Note:
Most of the dietary galactose is converted to glucose and goes to systemic circulation as glucose, very little galactose as such goes to systemic circulation.
ال tissue اللي بتحتاج galactose كتير بتصنعو من ال glucose وتأخدو من ال systemic.
So that performed galactose is not essential in the diet.
🌸 Importance of galactose:
1. Synthesis of lactose in lactating mammary gland.
2. Utilised in brain and nervous tissues for synthesis of glycolipids- cerebrosides and gangliosides.
3. Synthesis of glycoproteins and proteoglycans.
4. Synthesis of glycosaminoglycans.
🌸 Conversion of galactose into glucose:
Site: in the liver.
Steps:
يلا نمشي خطوة خطوة
1. Galactose phosphorylated and converted to Galactose-1-phosphate
عن طريق انزيم اسمو Galactokinase في وجود ال ++mg وفي وجود ATP ك مانح لل phosphate ف ح تتحول ATPل ADP. ونخلي في بالنا التفاعل دا irreversible.
2. Galactose-1-phosphate reacts with UDP-GLUCOSE to form UDP-galactose and glucose-1-p by Galactose-1-p uridyl transferase.
يلا نحن هنا اتحصلنا عن ناتجين من التفاعل ف ح نشتغل بس ب ال UDP-GALACTOSE.
3. UDP-Galactose converted to UDP-Glucose
عن طريق UDP-Galactose epimerase وبحتاج ل +NAD والتفاعل دا reversible.
4. UDP-Glucose converted to glycogen by glycogen synthase.
5. Glycogen converted to Glucose by glycogenolysis.
الصورة المرفقة ح توضح ليكم اكتر وتابعوا معاها خطوة خطوة😌👋
🌸 Conversion of glucose into galactose in mammary gland and lactose synthesis:
Lactose is a disaccharide formed of galactose attached to glucose by B 1-4 bonds, it is called milk suger.
🌸 Steps:
1. Glucose converted into UDP-galactose.
2. UDP-Galactose reacts with a molecule of glucose in the presence of lactose synthetase (also called galactosyl synthetase) enzyme to form lactose.
دا كلو طبعا بتحتاجو لي ال lactating mammary gland.
🌸 Galactosemia:
🌺 Definition: It is inherited disorder,in which there is increase blood galactose concentration due to inability to metabolize galactose in normal manner.
يعني شنو؟ يعني ال galactose ح يفضل زي ماهو وم ح يتحول الجلكوز بالتالي ح يزيد المعدل بتاعو في الدم.
🌺 Incidence: 1 in 18,000 live births.
🌺 Causes: Inherited enzyme deficiency of:
1.Galactose -1-P uridyl transferase.
النوع اللي بكون بسبب النقص في الانزيم دا بسموهو classical type وبحصل accumlation لل galactose في blood ,tissues مثلا زي ال RBCs, liver,spleen, kidney, heart ,lens of eye and cerebral cortex
2.Galactokinase.
والنوع اللي بكون بسبب الانزيم دا بسموهو minor type وبحصل accumlation in blood and tissues
3. Epimerase.
و النوع دا rarely.
🌺 Effect:
الزيادة في ال galactose دا ح تعمل لي الآتي:
1. Cataract (i.e opcity of eye lens):
Galactose in the eye is reduced by an enzyme called aldose reductase into galacticol( Dulcitol) , which accumlates causing cataract.
يعني لما يزيد ال galactose دا ح يخلي لي انزيم معين موجود في العين انه يحول ال galactose دا ل galacticol اللي هي دي الحاجه اللي بتعمل ال cataract يعني اتساع او تضخم في عدسة العين وممكن يصل ل injury of lens proteins.
2. Liver failure.
3. Mental retardation due to accumlation of galactose and galactose-1-P in cerebral cortex.
4. Galactosuria.
والحمدلله خلصنا😍👏
ان شاء الله في البوست الجاي ح اتكلم عن Fructose metabolism.
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