Newsgroups: sci.bio
Path: utzoo!utgpu!lamoran
From: lamoran@gpu.utcs.utoronto.ca (L.A. Moran)
Subject: Quiz time
Message-ID: <1991Apr24.153052.12686@gpu.utcs.utoronto.ca>
Organization: UTCS Public Access
Date: Wed, 24 Apr 1991 15:30:52 GMT



David Mikkelson posted some questions from a recent introductory biology
quiz at some school in California. I could not resist answering although
I will probably regret it. I teach an introductory biochemistry course but
my area of expertise is closer to molecular biology.


1. A "high-energy bond"
      a) absorbs a large amount of free energy when the phosphate group is
         attached during hydrolysis.
      b) is formed when ATP is hydrolyzed to ADP and one phosphate group
      c) is usually found in each glucose molecule; that is why glucose is
         chosen as the starting point for glycolysis.
      d) none of the above

The term "high-energy bond" is very imprecise but it is useful when 
describing biochemical reactions. A high energy bond is one whose hydrolysis
proceeds with a large negative change in free energy. The phosphoanhydride
bonds in ATP are typical examples of "high-energy bonds" (note that this is
not the same as bond energy). Answer (a) is wrong because it refers to
absorption of energy during hydrolysis and this is ambiguous. Answer (b) is
incorrect because ATP has one more high energy bond than ADP and not the other
way around. Answer (c) is incorrect because glucose does not contain bonds
that are readily hydrolysed. Thus answer (d) is correct. I suspect that this
question was poorly written and that answer (a) was the one that the
examiner wanted to be correct. 



2. When NAD combines with hydrogen, the NAD is
        a) reduced  
        b) oxidized  
        c) phosphorylated  
        d) denatured  
        e) none of these
 
Strictly speaking the NAD should be followed by a plus (+) sign to show that
it is the oxidized form. When it combines with a hydride ion (H-) it is
reduced. Answer (a) is probably the answer that was expected but if a 
a student of mine demonstrated that she knew the difference between "hydrogen"
and hydride ion then I would give her a mark for (e). The question is poorly
designed. I doubt very much that this little bit of trivia is important
in an introductory biology course.



3. The oxygen released in photosynthesis comes from
        a) carbon dioxide  
        b) glucose  
        c) ribulose biphosphate 
        d) water  
        e) atmospheric oxygen

The released oxygen is derived from the photolysis of water. Thus answer (d)
is correct. I can't see any serious problem with this question.


4. Which of the following has the most energy?
        a) AMP  
        b) ADP 
        c) ATP
        d) glucose
        e) NADPH

This is an impossible question for an introductory biology course. The 
molecule with the most "energy" is the one with the most covalent bonds. 
It is easy to understand this if you think about the amount of energy which
would be needed to make the molecule. The answer is (e) but I'm sure that
the examiner expected (c) because he/she really meant to ask which molecule
contained the most USABLE energy. The question should be dropped from the
exam.

David, can you tell who teaches this course (ie. who made up the exam) and
where it was taught? I would also like to know what textbook was used.


-Larry Moran
Dept. of Biochemistry