new_n_lost
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At which of the following sites is the characteristic triple helical structure of the collagen initially formed?
A. Extracellular space
B. Golgi body
C. Nucleus
D. Rough endoplasmic reticulum
E. Smooth endoplasmic reticulum
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| PGI2alpha
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golgi? coz thts the last place whr collagen goes before being secreted out of the cell
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| new_n_lost
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Anyone else wants to give it a try
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| mytime
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I was going to answer but anyways it's not imp. for me too. Just writing to tell u , u better know each n every step here, in this collagen formation then the post-transitional that follows. WHere Vit.C acts, inside or outside where Cu does, which enzymes. What deficiencies these can cause. What types of collagens, where. What disorders. Most common type and most severe ones.
U don't have to answer this one right now, GO READ ALL THIS UP first.......and then do it 10 times again.
GOOD LUCK!!!!!!!!!!! NNL this is a toast to u. (my l'le extempo post  )
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| hope4dabest
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D....but m not really sure..UW had explained this very well
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| new_n_lost
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PGI2alpha wrote:
golgi? coz thts the last place whr collagen goes before being secreted out of the cell
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| new_n_lost
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The correct answer is B.
Collagen formation begins with transcription of mRNA from appropriate DNA genes in the nucleus. While still within the nucleus, the mRNA is spliced. It is then transported through the cytoplasm to the ribosomes on the rough endoplasmic reticulum. Individual chains are translated on the ribosomes, with the ends feeding into the endoplasmic reticulum lumen. Within the lumen, glycosylation of the individual chains occurs. The material then moves toward the Golgi bodies (whose lumens are connected to the endoplasmic reticulum) where the triple helices of procollagen form. The procollagen is then secreted into the extracellular space, where cleavage of pro-peptides and cross- linking of different triple helices occurs, maturing the collagen.
The extracellular space (choice A) is the site of procollagen cleavage and cross- linking.
The nucleus (choice C) is the site of mRNA transcription and splicing.
The rough endoplasmic reticulum (choice D) is the site of chain translation and glycosylation.
The smooth endoplasmic reticulum (choice E) does not participate in collagen synthesis.
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| hope4dabest
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Hey...Now i am writing this form my notes which i jotted from UW "SPECIFIC PROLIN AND LYSIL RESIDUES ARE POST-TRANSLATIONALLY MODIFIED TO HYDROYYPROLIN BY PROLYL HYDROXYLASE AND LYSYL HYDROXYLASE RESPECTIVELY IN ENDOPLASMIC RETICULUM. VIT C IS REQUIRED AS COFACOR IN POST TRANSLATIONOL MODIFICATION.GLYCOSYLATION OF HYDROXYLYSINE RESIDUES AND SUBSEQUENT SELF-ASSEMBLY OF THE ALPHA PROCOLLAGEN CHAINS IN A TRIPLE HELIX BEGINS WITH DISULFIDE BOND FORMATION AT THE C TERMINUS WHILE THE ALPHA CHAINS ARE STILL WITHIN RER. ONCE THE TRIPLE HELIX IS COMPLETED, THE PROCOLLAGEN MOLECULE IS SECRETED FROM THE CELL OF GOLGI APPARATUS AND PROCOLLAGEN PEPTIDES AT THE N AND C TERMINI ARE CLEAVED BY THE EXTRACELLULAR PROCOLLAGEN PEPTIDASE..
Edited by hope4dabest on 12/14/07 - 11:39 PM
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| new_n_lost
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Yes this is a misprint from the Qbank and yes you are right hope I hadnt rechecked the answers for these questions.
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| new_n_lost
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I will be rechecking this one again.
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| cricket9014
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answer
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| cricket9014
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answer D (Alberts, pp 1098–1100. Junqueira, pp 106–110.) Nonhelical registration peptides at the ends of the triple helix prevent tropocollagen assembly in the RER, Golgi apparatus, and secretory vesicles. Collagen is synthesized as pro-α–chains, which are assembled into procollagen molecules (triple helix) in the rough endoplasmic reticulum.
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| doc4
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hey answer is D and not golgi
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| GoodGirl
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Central portion of procollagen has triple helical structure, formed in rough end.reticulum. That's how I know it. What is the source of this Q ?
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| spinal shock
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new_n_lost you are wonderful
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| macintosh
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| DRchromatin
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Answer is D.
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