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Are these right? Won't take long.. - (Nov/02/2007 )

Had an exam yesterday and would just like to know if I am right in a few MCQs...I have just written out the ones I chose:

affinity chromatography is a purification technique that:
separates proteins according to size

cellulose acetate electrophoresis indicates that albumin:
is -vely charged

the rate of enzyme catalyzed rxns is usually determined by measuring the initial rate of rxns because:
only the initial rate is simply related to the initial substrate concentration

Papain incubated with EDTA:
Activates enzyme activity by binding divalent metal cations

When acid is added to the rxn: ethanol + Nad+ <--> acetaldehyde + NADH + H+ the following is expected to happen:
Increases the conc. of NADH

interaction between cibacron blue and albumin is considered:

when the liver enzyme alcohol dehydrogenase oxidizes ethanol an increase in the absorbance of the solution occurs at 340nm. This is because:
NADH is produced during the rxn

In the lab where the enzyme papain is investigated, it was preincubated prior to assay to:
ensure that the reactive site cysteine was in the reduced form

I know there is heaps of q's but any1 that can tell me if they are wrong/right will be great...I just wanna make sure I have got the marks for these so having the ans. to this post will be MOST appreciated!!

Thanks you to whoever answers!!


Not very good.

#1, 3, 4,, maybe 5 are not correct.


QUOTE (genehunter-1 @ Nov 3 2007, 03:53 PM)
Not very good.

#1, 3, 4,, maybe 5 are not correct.

for number one the other options were:
explots an unique property of a protein
separates proteins according to their hydrophilicity
involves ion-exchange chromatography
results in protein samples that are denatured

so what was the ans...the other ones didn't sound right to me (all all??)

and number 4 the other options were:
have no effect on enzyme activty
activate enzyme activty by modifying the casein substrate
inhibit enzyme activty by binding divalent metal cations
inhibit enzyme activty by binding divalent metal cations...

the other q's i can accept as wrong but ^^ i would like to konw the ans..


#1 is A. The affinity binding property to a specific ligand is exploited.
#4 is A, and possibly B. A: Your enzyme has an air sensitive group at the active center which is SH. DTT or beta-mercaptoethanol activates the active center SH group by reducing it. O2 does the opposite. Heavy metals act as catalysts and help O2 to oxidize the SH groups. EDTA binds to heavy metals and neutralize these hamful substances. But ETDA itself has no effect on the enzyme directly.
B: The substrate is known to have many Ca2+ ion bound to the anionic groups on casein, which may reduce the enzyme accessibility to the protein. I am not 100% sure about this, just a guess. Check your textbook or notes.


#5 is likely not correct. The equation is: ethanol + Nad+ <--> acetaldehyde + NADH + H+
If you add acid, it means that H+ will increase. Remember that the reaction will run towards the side that will reduce the stimulant (I am no sure if that is the right expression, but it is like: if a reaction releases heat, then put it in cold then it will run faster). So in this case, more H+ means that the reaction will lean toward reducing the amount of H+, that is towards ethanol + Nad+, so it should be less NaDH instead.


Acid could set the reaction out of the optimal pH for the enzyme as well.


QUOTE (biology_06er @ Nov 2 2007, 07:10 PM)
interaction between cibacron blue and albumin is considered:

this is group specific affinity.