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Post by Nick on Sept 6, 2006 23:02:48 GMT -5
Please post the question, answer choices, and correct answer in this thread.
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Post by Jillian Wall on Sept 7, 2006 19:11:25 GMT -5
T or F (explain why)? A student has 100ml of a .1M of histadine at its pI. 100ml of .05M HCl is added. The final pH is 7.2. (if false explain why)
I think this covers a few bases.
-Jill
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Post by Nick on Sept 9, 2006 12:38:39 GMT -5
All of the following enzymes use acid-base catalysis as a mechanism of enhancing the rate of the reaction EXCEPT:
a) Lysozyme
b) Carbonic anhydrase
c) Chymotrypsin
d) Carboxypeptidase
Answer: C. Chymotrypsin is an example of a serine protease that uses covalent catalysis for rate enhancement.
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Post by Nick on Sept 9, 2006 13:01:20 GMT -5
High levels of which of the following are tested for the determination of broken bones?
a) Hydroxylysine
b) Hydroxyproline
c) Creatinine
d) Phospho-enol-pyruvate (PEP)
Answer: B. On page 9 in the notes when he is talking about the hydroxylation of proline, he mentioned how his daughter was sent home after the doctors told her she didn't have a broken bone. But a few days later when they saw elevated levels of hydroxyproline they had her come back in and sure enough there was a fracture.
Creatinine on the other hand was mentioned on page 38 of the notes. It is excreted in the urine and levels of it can be used to determine how much muscle mass there is or if there has been damage to the muscle.
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Post by Kristina on Sept 9, 2006 14:41:55 GMT -5
Creatine~Phosphate + ADP --> Creatine + ATP
Is the reaction spontaneous? What will the ratio of pdts to reactants be at equilibrium?
Answer: Look on page 38 of your notes and email me if you have any questions. keaton04@gmail.com
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chad
New Member
Posts: 6
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Post by chad on Sept 9, 2006 22:20:44 GMT -5
One would find all of the following interactions stabilizing an enzymes quaternary structure except:
A) Hydrogen bonding
B) Disulfide bonds
C) Ionic links
D) hydrophobic interactions
Answer: B) All interactions of between multimer subunits are non-covalent. Disulfide bonds (covalent) are important in the stabilization of tertiary structure. (Pages 26 & 27 of notes)
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Post by jcartinella on Sept 10, 2006 10:55:38 GMT -5
This is the answer to the question I posted:
Again, here's the composition of the peptide:
val, lys, ala, met, met, phe, cys, his, arg, ile
After Edman's degradation you should know the following:
N-met-ala-(val, lys, met, phe, cys, his, arg, ile)-C
After Trypsin you should know the following:
N-met-ala-val-lys-(met, ile)-arg-(his, phe, cys)-C
After CNBr you should know the following:
N-met-ala-val-lys-ile-met-arg-(his, phe, cys)-C
After Chymotrypsin you should know the whole sequence:
N-met-ala-val-lys-ile-met-arg-cys-phe-his-C
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chad
New Member
Posts: 6
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Post by chad on Sept 10, 2006 12:16:58 GMT -5
Which of the following is responsible for increasing the activation energy of the following reaction ATP + H2O => ADP +Pi?
A) Ca++
B) ATP dismutase activity
C) A low [ATP] conc.
D) A lower temperature
E) Presence of glucose
Answer: A) Ca++, as well as Mg,Zn,&Cd, chelates ATP. This means that the + charge on the metal ion helps neutralize the - charges on the phosphates thereby minimizing the charge repulsion b/n phsophates. As charge repulsion is one of the driving forces for the release of Pi from ATP, neutralizing this effect will make the reaction less kinetically favorable by increaseing the Ea (page 37).
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chad
New Member
Posts: 6
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Post by chad on Sept 10, 2006 12:38:39 GMT -5
Which of the following molecules has a largely negative delta G due to the effects of tautomerism?
A) Thiol-esters
B) Guanidium phosphates
C) Enoyl phosphates
D) Esters
Answer: C) look at page 38 of the notes. The enol formed by the release of phosphate from PEP tautomerizes thereby decreasing the concentration of this product making the reaction highly favorable in the right direction (thus a large neg. delta G).
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Post by Nick on Sept 10, 2006 14:48:33 GMT -5
If you perform an Edman’s degradation and get lysine, tyrosine, and arginine on a TLC plate, what is most likely the amino terminal amino acid?
a) Lysine
b) Tyrosine
c) Arginine
d) Proline
e) None of the above
Answer: b) Tyrosine. PITC tags all primary amines, so in addition to the amino terminal end, it will also tag lysine and arginine if they are present in the protein since their R groups contain primary amines. The only reason tyrosine would show up on a TLC plate after Edman's degradation would be that it was at the amino terminal end of the protein.
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Post by Nick on Sept 10, 2006 15:06:28 GMT -5
What makes the brain so efficient in absorbing a large portion of blood glucose?
a) Vmax/Km is higher in the brain
b) the BB isozyme has a higher affinity for glucose
c) it has more GK than other tissues
d) it has more HK than other tissues
Answer: D. p. 63 in the notes
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Post by avinashb on Sept 10, 2006 20:24:26 GMT -5
All of the following are true for carboxypeptidase, EXCEPT:
a. it is an exopeptidase
b. it involves acid-base catalysis
c. if sequencing yields gly, ala, phe, the corresponding peptide is gly-ala-phe
d. it utilizes Zn++
Answer: c (because it cleaves from the carboxy terminal, the corresponding peptide is: phe-ala-gly).
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Post by ccharles on Sept 10, 2006 23:04:47 GMT -5
What does Vitamin A and physiological salts help to re-form?
a. alpha helixes
b. LDH
c. Collagen fibrils
d. beta sheets
answer: C, page 25 of notes collagen role in bone formation
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