Thursday, 22 January 2009

The end in sight

Branches and trees covered in frost
While the public face of the blog has been getting all technical about Hepatitis B and celebrating 200 posts, I've actually been sitting at my desk stuffing my brain full of Facts. The heart develops from the mesoderm germline. The cardiogenic mesoderm induces the liver to form from an adjacent stretch of the primitive gut. The kidney develops from a process of reciprocal induction between the metanephric mesenchyme and the ureteric bud sprouting from the Wolffian duct.

The first exam was Molecular Pharming, and took place, as all the lectures had, on the main campus rather than on the Biosciences satellite campus. This is about 20 minutes further from home for me, and I'd never been to the building where the exam was, and on the few occasions when there had been trouble on the motorway, the journey takes about three hours instead of one. The exam was scheduled to start at 9 a.m. I left home at 6.30 - which would probably still have made me late if there had been any trouble on the motorway. The first version of Golden Rice substituted an enzyme from daffodil but didn't produce enough vitamin A. The second version was more successful, and an enzyme from maize was chosen from several based on the strength of the yellow hue in culture. Regulatory, organizational and political factors are still holding up widespread field trials of vitamin A-enhanced Golden Rice.

Immunology was next, and I actually went to see the lecturer to check out a few things that I couldn't make sense of from the lectures or the books. In the event, I found the exam too easy. What I mean by that is: I aim high in exams, putting a lot of effort into revision. And I mean a lot of effort. If the exam is too easy, then people who haven't done much work can get similar marks, and I resent that. I want lazy people to fail. That doesn't make me a bad person. Mast cells are stimulated by antigen-IgE complexes and by C5a complement. The role of complement in the blood is to enhance phagocytosis by opsonisation, create a membrane attack complex to lyse bacterial pathogens, and to help activate B lymphocytes to produce antibodies.

Yesterday was biochemistry, and satisfyingly difficult. I wrote quite a lot about the filaments that form the cellular cytoskeleton, which enable cells to move about, change shape, transport chemicals about and pull chromatids apart when cells divide. It does occur to me that this is an area of knowledge that has little practical use, but I do find it so interesting and it all adds up to a wide-ranging education. Focal contacts allow signals from the extracellular matrix to be sensed by a transmembrane integrin dimer, resulting (if favourable) in the formation of a protein complex recruiting actin microfilaments that are able to do work, pushing the leading edge of the cell forward.

The last exam is Endocrinology and Metabolism tomorrow, and I was feeling a bit aggrieved that it runs from 4.30 to 6.30 p.m. until I found out that some people have exams on Saturday. The parathyroid gland secretes parathyroid hormone in response to low blood calcium, which acts on bone to release calcium and phosphate into the circulation, and on the kidney to retain more calcium but excrete the excess phosphate in the urine. The kidney also produces more active vitamin D, which enhances calcium absorption in the gut.

I'm going out for a curry afterwards, then off to visit Lola II for the weekend. With hardly time to take a breath, the new semester starts first thing Monday with the first lecture of a Food Composition module.

1 comment:

Don't Bug Me! said...

I wish you were one of my students. They always complain that my exams are too hard, even when I point out that that is the whole point of an exam - if they were all easy, why bother?