Monthly Archives: October 2014

The other day in class I misspoke when I equated Peptidoglycan with Proteoglycan. Being similarly named, I got tongue-tied and confused them and then further confused myself when I tried to clarify. My problem at the time was that I looked to the etymology of the two words to distinguish them and came up short – this is the kind of faulty ‘on your feet thinking’ that gets teachers and politicians into trouble.

So, to correct things for the record, Peptidoglycan refers to the sugar / amino acid polymer making up the cell wall of bacteria. Peptidoglycan is synthesized in the cytoplasm as monomeric units that are then transported to the cell wall for inclusion.

Because animal cells do not contain peptidoglycan, a number of (naturally occurring) antibiotics target it, or the enzymes that operate in its synthesis. The use of peptidoglycan is a ‘clever’ way that evolution has discovered of escaping immune / enzymatic responses because it includes L-Amino Acids that are unused in protein synthesis by any organism and therefore not susceptible to any typical proteases.

The other molecule, Proteoglycan refers to a complex of protein that is ‘decorated’ with sugars, such as the ones those that are added and modified in the ER / Golgi of Eukaryotic cells.  Specifically, proteoglycans are “found in all connective tissues, extracellular matrix (ECM) and on the surfaces of many cell types. Proteoglycans are remarkable for their diversity (different cores, different numbers of GAGs with various lenghts and compositions).”

A good review of the various proteoglycan structures can be found here.

Just a quick post today to point to a set of older entries discussing the Lac Operon.

The first does’t have much, but it does link to an animation that is useful in presenting how the operon and its regulators react to changing conditions.

The second is longer and ends with a graph of cellular metabolism that does a good job of showing what happens when one substrate runs out resulting in a switch to the new substrate (glucose –> lactose).

The last is probably the best as it summarizes the information on the other two and includes some cartoons that I feel clearly show the conditions the cell is living in and effect this has on the cell’s sugar use.

This may also be a good time to point out that the banner above includes a link to a hyperlinked table of contents. Although not all my posts have been categorized, it does have quite a few and they are organized by category. I encourage my students to take advantage of this resource if there are subjects they would benefit from reading a bit about. I’ll of my best to keep working on this page to include at least the more substance-rich posts.

Perhaps to the location of extra credit possibilities?

Have you seen this man?

Things that show up on Jeopardy Review often show up on Exams. But if you just want a point for the quiz tomorrow (General Bio), then you might want to consider the history behind this painting.

I used to live just a little ways up the river from this

The recent spread of Ebola this year has been a great opportunity to examine both the biology of the virus and epidemiology of infection. In my classes, this topic has come up regularly with each news event. As of this time, it’s still just a curiosity to watch from afar and see how epidemics get started, balloon into larger problems, interact with the global transportation system, spread into pandemics, provide insight into how different political and health organizations deal with the problem.

Typically Ebola has been a self-limiting infection. Because of the high death rate and remote locations outbreaks have occurred in, few people have been able to get infected and make it out ‘to civilization’ alive. Those who have presumably were no longer carrying the virus when they did come into contact with the wider world. I imagine these outbreaks sort of like forest fires erupting on tropical islands: The fire ignites, burns the trees on the island and then dies away when there is no more fuel to consume.

This year, the fire has burned more brightly than ever before, scattering embers into the wind. Travelers and healthcare workers alike have been exposed and left the site of the epidemics with the virus within them. Unfortunately, these individuals have helped to spread Ebola Virus far from Africa. Often these people arrive in foreign countries as patients looking for superior healthcare, and in large part they have received treatment without spreading the virus to others.

The US has recently seen its first case of Ebola arriving in the country ‘unbidden’ – meaning it was not someone who was brought to the US for treatment, but rather was someone who arrived in the US during the incubation time of the disease. Shortly after, the first documented case of Ebola transmission in the US occurred.  It’s possible that you’re hitting the panic button now – or you’re waiting to see how things will develop as a test of the health protocols for dealing with this sort of thing. Or, perhaps you’re a singer and you get to mouth off in total ignorance .

In the meantime, take a look at this website. It has some excellent, well organized descriptions of the virus, its transmission, and the disease it causes.

How did they get Madagascar?

Check out my new post on sex and violence in slasher films at my film blog.

A student in my Microbiology class brought up some new information running about the internet about the Gardasil vaccine against Human Papilloma Virus (HPV) and concerns about its safety. I have to admit that my first reaction was suspicion. There are a lot of ‘Anti-vaxxers’ out there who have made it their mission (for unknown reasons) to discredit or simply ‘raise questions’ about particular vaccines. More often than not, the vaccine in question is MMR, and the distrust is linked to the Andrew Wakefield article originally published in the Lancet – although, it has since been retracted by all the authors except one (Wakefield) and the Journal itself.

When vaccines started appearing directed against HPV, a new set of questions came to the fore. One major reason for this is that the vaccine targets a sexually transmitted disease (STD). Another issue was the vaccine maker, Merck’s insistence that this vaccine be adopted as one of the many required for public school admittance.

What my student was referring to is a video put out by the Health Sciences Institute, of which she is director. I was eager to look this up and write about it, regardless of the information. Especially because I use HPV as a model disease and Gardasil as a model vaccine in my microbiology class. If there was, indeed, a problem with the vaccine, I wanted to know about it – if for no other reason, to make it a teachable moment.

Unfortunately (for me), this has already been very well researched and written about on Snopes. I strongly suggest anyone who is concerned by the vaccine or these rumors to check out that article. I would also suggest looking at another website’s article about questionable scientific organizations and the views that they promote.