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Biochemistry Help


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#1 Biochemhelp

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Posted 5 March 2013 - 09:13 AM

Can anyone help me solve these practice questions or give advice?

 

Biochemistry Practice Questions.PNG


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#2 CaptainPanic

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Posted 5 March 2013 - 09:33 AM

This is homework. We do not answer homework questions straight away. You have to show us what you did to try to solve the question so far.

 

Also, I used my moderator powers to remove the double post. :)


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#3 LondonDispersion

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Posted 5 March 2013 - 06:47 PM

As far as advice goes, maybe we can get you started (without answering your HW for you).

 

Let's look at #2.  Do you know what the building blocks of proteins are?  Do you know what the building blocks of lipids are?

Once you figure out these 'building blocks', the answer to question #2 should come very easily to you.

Want to explain to us how much you know about the components of proteins and lipids (fats)?  From there we can help you a little further along.


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#4 BabcockHall

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Posted 5 March 2013 - 11:56 PM

With respect to 4, what do competitive inhibitors generally do?


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#5 LondonDispersion

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Posted 6 March 2013 - 07:49 PM

With respect to 4, what do competitive inhibitors generally do?

 

Generally speaking:

Inhibitors are molecules that affect enzyme activity.  There are three kinds of enzyme inhibitors: competitive, noncompetitive, and uncompetitive.

 

*Competitive inhibitors (like sulfa drugs and penicillin), true to their name, compete with substrates to bind to the active site of the enzyme they're after.  This prevents the the substrate from binding with the enzyme to catalyze and/or complete a reaction.

Oftentimes, this halts a metabolic process (as question 4  is getting at).

 

A great example of a competitive inhibitor is penicillin; a well-known antibiotic.  Bacterial cell walls are made of peptidoglycans -- N-Acetylmuramic acid (NAMA) and N-Acetylglucosamine (NAGA).  Bacterial cell walls are formed by the cross-linking of NAMA and NAGA.  In most bacteria, the cell wall is required for the bacteria's survival.  Competitive inhibition facilitated by penicillin kills bacteria by competing for the active site on the enzyme that facilitates the NAMA-NAGA linking in the bacterial cell wall, thus preventing the cross-linking of peptidoglycan and this causes the cell wall to weaken, lyse, and the bacteria to die.

 

The paragraph that starts with the asterisk (*) is the direct and simple answer to your question, in case you weren't looking for specifics.


Edited by LondonDispersion, 6 March 2013 - 07:50 PM.

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#6 BabcockHall

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Posted 7 March 2013 - 04:33 PM

LD, Thanks.  I should have said that my question was directed to the OP to help with question 4.  Penicillin reacts covalently with the enzyme in question (sometimes called transpeptidase), which is not true of all competitive inhibitors.  Sometimes people include one or more additional classes when discussing inhibitors of enzymes.  One such class is irreversible inhibitors, and both penicillin and asprin fall into this category.


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