Cellular UPS and bad design

As I have mentioned in class, I think that bacteria and viruses appear to possess  features consistent with the idea that they are designed to deliver agents to cells.  For instance, their size is conducive to cell interaction and many possess elaborate motors , docking and delivery systems.  In fact, the bacterial flagellum which is often advertised as having one function, actually demonstrates many functions, i.e. it is a docking/binding agent as well as a motor, it also appears to be a receptor in some instances.  Thus the flagellum demonstrates co-option; it has more than one function,  an idea that many intelligent design theorists don’t like.  In addition some bacteria can control the actin polymerization inside cells inducing the cells to make “cellular arms” or pseudopods.  Thus they  induce the cell pseudopods to engulf them and they enter the cell in this manner.  Recently, researchers have used  bacteria to deliver a virus to a cell which induced profound genetic changes in the cell.  Viruses themselves possess several elaborate mechanisms for engaging cells and entering cells.  Viruses not only deliver genetic information to cells, but they can deliver proteins, they can control intracellular biochemistry and they can deliver membranes and membrane proteins.  Take for instance the flu virus.  It is an enveloped virus.  Technically when it leaves a cell it takes along some membrane from that cell.  Could it be that everytime you get a flu, you also get some proteins and membrane components from your friends?   What are the long term and short term implications of this?  But then again, viruses and bacteria can cause lots of problems.  If these creatures were designed as extracellular delivery organelles, is this the best design?.... because it appears that with a few "slight modifications" they can become agents of cellular destruction.

Questions:

1 Discuss the microbial extracellular organelle theory as described above.  What are its strengths and weaknesses as a theory?

2 If bacteria and viruses are designed delivery agents, why does our immune system try to eliminate them?  Or does it?

the dreaded dihydrogen oxide cell toxin: beware!!

Dihydrogen oxide is one of the most lethal cellular toxins.  It kills cells by causing them to swell uncontrollably and then burst, or in some cases to shrivel up like a crumpled piece of paper.  However most all cells on earth have been able to resist this toxin by using a membrane protein to prevent its deadly actions.  But even more interesting dihydrogen oxide or water is required for life and the aquaporin channel helps maintain a non-lethal concentration of this precious but deadly fluid.

Aquaporin is a fascinating integral membrane protein.  It is able to "filter" water into the cell by keeping other polar or charged molecules around the same size as water  out of the pore.  Plant, animal and bacterial cells have aquaporin channels. 

Questions:

1 How does aquaporin operate as a selectivity filter?  What would happen to cellular metabolism if it did not operate as a selectivity filter?

2 The complexity and requirement of aquaporin for cellular life appears to be a problem for the evolution of the first cells.  Or is it?  Some plants cells can take in water without aquaporin.  Could this represent a more ancient water controlling mechanism?  Check it out and comment on what you have learned.

cell suicide and the schizophrenic Jason Bourne organelle

We are discussing the lipids and proteins which make up the membranes in cells in lecture.  One of the most bizarre membrane proteins is called the mitochondrial permeability transition pore (mPTP).  This is a cluster of proteins which connect the inner mitochondrial membrane with the outer mitochondrial membrane and forms a pore.  The pore only  forms briefly under extreme cell stress conditions and essentially really messes up the mitochondria so that it reverses its function, and begins consuming ATP which  usually kills the cell.   In many cases this activity leads to apoptosis also called programmed cell death. This drastic measure often occurs after local cellular stress or stress of internal organs like during a heart attack.    Just like Jason Bourne in the Bourne Identity, the identity of the mitochondria is difficult to determine, it is a unique mystery organelle in many ways, and like Bourne, it  commits violence when stressed out....or is it that it commits violence to protect itself? Just what could the mitochondria be protecting? 

Questions:

1 What are the different ways that a cell can die?

2 What is apoptosis?  What are its benefits?

3 What would be the advantage to having the vital energy producing organelle also double as a death organelle?

4 Considering the idea that the mitochondria is a specialized internal bacterium, are there parallels in function between  mitochondria and extracellular free living bacteria with respect to energy production and promotion of cell death?

membranes of the microbial cockatrice

A cockatrice was a  wild dish served  at medieval  banquets.  It was a cooked dish of a rooster fused to a suckling pig.   Archaebacteria, as suggested by some microbiologists, are a microbial version of the cockatrice, since they appear to have genomes composed of both prokaryotes and eukaryotes.  

However, what is even more interesting is the different kinds of lipids and structures which make up the outer membrane and walls of the archaebacteria.  Some archaebacteria have monolayers rather than bilayers in their membranes.  They also have different lipids suggesting that the biochemistry involved in making archaebacteria lipids is very different from both eukaryotes and prokaryotes.  Their cell wall also contains something called an S-layer which is an intriguing structure.  Even more fascinating the flagellum they display is constructed differently from the flagellum of eubacteria.

1 Explore the structure of the archaebacterial monolayers.  How does this contribute to life in the extreme?

2 What is an S-layer and how does it contribute to cell function?

3 We discussed the problems inherent in trying to assemble a flagellum from pieces secreted from the eubacterial cell.  How is this problem solved in the archaebacterial flagellum? Or is it solved?