Kaplan FL #9 Mice Problem

[Jay2910]

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Hello everyone,

Here is the passage that I am having trouble with . . .its on Kaplan #9:

And here are the questions that I don't get:

47) Based on the information presented in the passage, which of the following molecules will be the best candidate for a competitive inhibitor of sperm-egg interactio in mcie?

A) Oligosaccharide with N-acetyl-glucosaminyl residues
B) oligosaccharide w ith alpha galactosyl residues
C) Antibody to Sp56
D) Antibody to Beta-galactosyltransferase

I figured that since, B galactosyltransferase mutants pose the max problem wwhen it comes to fertilization( both in the number of egg/ sperm bound according to table #2 and in the fact that beta males were infertile in table 1), that an antibody against this would be most effective.

Is the answer not D, because that is what we are trying to inhibit in the fist place?

Second question:

The most reasonable conclusion that can be draw from the experiments described in the passage is that:

A) strain alpha can reproduce itself just as effectively as wild type
B) strain beta males are infertile because their sperm cannot attah to eggs
C) Beta galactosyltransferase is needed for effective attachment of sperm to an egg
D) alpha galactosyltransferase is unlikely to play a role in fertilization

I chose A but the answer is C.
I understand why it could be C . . .but why can't it be A? What is the whole point of table 1 in the first place? Is the top of the table ( where it says Males and females . . .are they the wild type?)

Thanks in advance!

 

[enervate]

For question #47, competitive inhibitors compete with the substrate for the active site. An antibody would not bind at the active site and would therefore not be a competitive inhibitor for the enzyme. Instead, you would want a molecule that mimics the substrate. In this case, that would be an oligosaccharide with non-reducing GlcNAc terminal residues since it closely resembles the substrate for beta-galactosyltransferase. You were correct in inferring that we are trying to inhibit beta-galactosyltransferase but you missed the emphasis on competitive inhibition. Be sure to review the main types of enzyme inhibition: competitive, noncompetitive, uncompetitive, and suicide.


For your second question, the experiments were designed only to determine which enzyme is required for the sperm to bind the egg. Given the results, you should only be making conclusions that explicitly conform to the experimental design. In these experiments, alpha- and beta-galactosyltransferase enzymes were broken. Therefore, a conclusion can only be reached that addresses whether or not either enzyme breaks fertility. Any other logical inferences based upon data produced by these experiments are not explicitly supported by the experimental design and another experiment would have to be designed and conducted before any conclusions could be made about those inferences. Separating inferences, theories, assertions and opinions from fact-based conclusions is essential to effectively navigating scientific literature.