Tuesday, April 28, 2009

Are You as Smart as a Second Year University Student? Q6

Are You as Smart as a Second Year University Student?

Question 1
Question 2
Question 3
Question 4
Question 5
Today was the final exam in my introductory biochemistry course. It was kinda sad because it's the last year I'll be teaching this course.

Here's a variation on one of the questions. How many of you know the answer?
There are two basic strategies in polymerization reactions: head growth and tail growth. For each of the following polymerization reactions identify whether it is an example of head growth or tail growth.

a) DNA synthesis
b) starch synthesis
c) fatty acid synthesis
d) protein synthesis

Bonus points for Sandwalk readers if you can explain why it's important for some polymerization reactions to use a tail growth strategy.


  1. Head tail tail tail? It's been two years...
    It's too bad you won't be teaching bch242 anymore, I liked your section the best.

  2. I don't even understand a question. What is this esoteric heads-tails and why is it important?

    I know basic chemistry of all four types of polymereizations listed but the heads-tails still makes little sense. To me, anything that comes out in a polymer first is head and the atom that gets derivatized during polymerization is a tail. Hence, *any* linear synthesis is tail-to-head (or head-to-tail, depending on convention). Sounds like a stupid question that has something to do with memorizing someone's silliness and nothing to do with understanding biochemistry.

  3. I was curious so i googled. Has to do with the monomer's reactive bond consumes it to attach itself or as spot to attach the next monomer. In one case some other intermediate step sounds necessary to reform the bond to use for further expansion.


  4. Ah, another of today's exam questions. Now I can check to see if I got them right. I put:

    DNA synthesis: Tail
    Glycogen syn: Tail
    FA syn: Head
    Protein syn: Head

    DK, Head and Tail growth are distinguished by the location of the high-energy bond that drives the polymerization reaction. For tail growth, the energy is on the incoming monomer. In head growth, the energy driving the reaction is in a high energy bond on the growing chain and not on the incoming monomer.

    Prof Moran taught me that and so I hope my explanation does him justice. That's no guarantee my answer is right.