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العودة   منتديات الكيمياء الحيوية للجميع > الكيمياء الحيوية > المسـارات الايضية - Metabolism
 
 

المسـارات الايضية - Metabolism Anabolism & Catabolism

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قديم 03-20-2008, 07:26 PM   #1
mr.biochemistry
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افتراضي (lipid as a major source of energy ( a series

Hi enery one i am Mr.biochemistry as u all can see
I am a medical students who is in love with biochemistry
and i will be happy to contribute in this forum
and share with u and from u the knowledge

this topic as u all can see is a series of episodes about lipid and i will try to make the best of it
episode one

as we all know from elemntry school that lipid and specifically
triacylglycerol or commonly known for triglycerides is the major source of energy
but did we ask why ?
in case if u didnt I will be glade to tell u why
first becuz it is highly reduced compound forming alot of NADH
second it is largly anhydrous that it needs no H2O to be sored

by that i mean the famous and well know triacylglycerol or commonly known as triglycerides

i wanna discuss with u guys the pathway by wich the the TAG for short
is degraded to my first love AcetylcoA
wich is the final product of all catabolic pathways that is the substrate of Krebs cylce

let start from the beging

when a person ingest a meal that has lipid whatever it was
Cholestryl ester phospho lipid it needs to be hydrolyzed and degraded to smaller particles that is possible to be absorbed by intestinal cells
so for this to happen when enzymes that r acapable of degrading tiacylglycerol
there r two classes of lipid hydrolyzing enzyme
first there is acidic stable
gastic lipase and lingual lipase
these enzymes function in an acidic medium such as stomach
so TAG r broken down in stomac but not all TAG just the short and medium chain

second basic stable
these r pancreatic lipaeses
the r produced by the exocrine portion of pancrase and they r secreted in the duodenum

but here we have a problem
that the partially digested food is acidic due to the HCL in the stomach
and the hydrophobic nature of the lipid as we all know

so
the body has a an amazing mechanisim to solve these to problems
first concerning the acidity of the food the intestinal cells will be stimulated and it will secrete a hormone known as secretin that will make the pancrease secret HCO3
bicarbonate wich will neutrilize the acidity

second concerning the hydrophobicity
partially digested protein will stimulate the intestinal cells to secrete a hormone know as CCk that will stimulate the gallbladder to secrete the bile wich act as detergent
like the famous soap farry
that will help the pancreatic enzymes to anchore to TAG and degrade them into a compound
2 fatty acids
and to monoacyl glycerol
by that we will conclude that the structure of TAG is

a backbone made of glycerol esterified to three fatty acids

after that the lipd all not just TAG will be absorbed by intestinal cells as a mixed micelle
like this

it is absorbed passivly without the need of ATP

after that the fatty acids will be activated by the action of acyl coA synthtease
and reassembled into triacylglycerol as seen below

then it is packed in a chylomicron >>>> a lipoprotein
again becuz of its hydrophobicity
then it passes through lacteals a lymph vessel in the mucosa of intestinal cells
after that it will pass to the thoracic duct then to left subclavin artey then to blood stream


End of episode one

regards
Mr.biochemistry



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قديم 03-20-2008, 10:56 PM   #2
يحي
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افتراضي رد: (lipid as a major source of energy ( a series

شكرا




   
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قديم 03-20-2008, 11:24 PM   #3
mr.biochemistry
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mr.biochemistry غير متواجد حالياً
افتراضي رد: (lipid as a major source of energy ( a series

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وترى ما سوينا الا الواجب



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قديم 04-04-2008, 01:47 PM   #4
سونهام يغمور
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افتراضي رد: (lipid as a major source of energy ( a series

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