Thursday, October 12, 2006

Another Question for the crowd to kick around.

Update 30th October
Thanks for putting in questions from the list given in the study Question list not posted here.

THIS IS THE PLACE WHERE I ANSWER THEM, and will happily answer any more that are placed in the comments.

-------

Compare and contrast fructose syrup and steroid manufacturing processes as used in industry.


Both compare and contrast please.

Labels: ,

1 Comments:

Anonymous Anonymous said...

PART ONE OF RESPONSE TO RE METABOLIC analog Q,
Hypothesis:
"If histine is overproduced this creates a negative feedback inhibiting the first enzyme by histine binding to the active site of the enzyme. If the histine analog comes along this kills the first enzyme resulting in a mutant enzyme that will not allow histine or its analog to bind.

p-E1-P-E2-his

Is this why it is important to select mutants in which can grow on medium containg histine analogs?"


THIS SUGGESTED ANSWER/COMMENT IS VERY USEFUL AS IT SHOWS A MODEST UNDERSTANDING OF WHY ANALOGS ARE USED. SOMETIMES WEAK ANSWERS BEFORE AN EXAM ARE USEFUL TO PREVENT THEM APPEARING IN THE EXAM

The main problem is this statement which is misinformed and confusing but typical of exam answers by mainy poorly performing students:

"If the histine analog comes along this kills the first enzyme resulting in a mutant enzyme that will not allow histine or its analog to bind."

(Yes I know comments in a blog are tricky to get right, even to spell corectly!)

1. IT GIVES NO INDICATION of the student knowing how the full range of mechanisms by useful mutants can be selected by analogs- the inportant point being their action on OTHER enzymes than the first step in the (histidine) pathway in some cases. This should not be ignored. The most essential point not stated is that the analogues are toxic in some unspecified way because they mimic the natural compounds in binding to some essential esseme. For amino acids this is some step in protein synthesis usually.

2. This could be called the FALSE-FEEDBACK INHIBITOR hypothesis. It can sometimes be true BUT ONly SOME analogues are effective inhibitors of the first step in a pathway. The hypothesis is not outlines clearly and fully, with all the logic of mutant selection explained, and its the logic that the instructors are setting the questions for, and the only way to test good logic is a dialog like this. It's called a Socratic Dialogue.( Plato, 350 BC).

3. BUT Certainly the point that ONE desired mutant will be altered so that histidine will not bind to the first enzyme is very relevant and an essential part of an answer. GOOD.

But you may get other types of mutant with anologues - Which ones?

October 31, 2006 8:14 am  

Post a Comment

Links to this post:

Create a Link

<< Home