Cell%20Physiology%20of%20Disease%20A)Good%20Parasites%20Gone%20Bad%20%20B)Weak%20Parts%20Make%20Weak%20Machines

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Cell Physiology of DiseaseA)Good Parasites Gone
Bad B)Weak Parts Make Weak Machines
Professors Michael Sheetz, 713 Fairchild,
ms2001_at_columbia.edu Julio Fernandez, 1013
Fairchild, jfernandez_at_columbia.edu Teaching
Assistant Tim Marmo, tpm2003_at_columbia.edu
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Plan for Course
Jan. 21-March 8 Cellular Physiology of
Pathogens March 10 Mid-term March 22-May 3
Physiology Diseases of Nerve and Muscle Final
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Grading
Mid-term 33 Final 67 Exams will be written
problems analogous to the problems given at the
end of each lecture syllabus. Extra Credit
There will be extra credit assignments that can
add up to 20 of the final grade.
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Office Hours and TA Discussions
Dr. Sheetz 713 Fairchild Tuesdays
1130-1 Questions from the lectures or the
syllabus Tim Marmo 800 Fairchild Thursdays
410-6 Discussion of the problems at the end of
each syllabus. It is most beneficial if you have
worked on the problem.
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Cells have been around for about 2 billion years.
Just imagine the sophistication of PDAs in 2
billion years
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This is a comparison of the identity between
sequences of human hemoglobin and other species
as a function of the time since they diverged in
evolution. Note the sequences of human and tuna
hemoglobin are 55 identical because they evolved
independently for 450 million years.
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Systems Engineering and Cells
Systems Engineering in Chemical Engineering
involves the optimization of a process for the
production of a chemical from raw material Cell
Selection The process of selection of cells for
survival with limited resources or changing
environmental conditions results in a similar
optimization. Computer or Automobile Evolution
Many commercial products have evolved similarly
from a basic functioning unit to a highly
sophisticated system with many engineered
features.
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Cell Optimization and Robustness
Robustness in the context of cellular functions
means that the important task can be completed
even as conditions vary. Some of the obvious
variables for cells are listed below

1. number of proteins per cell
2. salinity and pH
3. temperature
4. nutrient level
5. environmental factors.

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Engineering Cells for Robustness
Compartmentalization of Functions It is much
easier to perform a complex function if the local
environment can be customized Modularity in
Functions If we consider highly engineered
items, they typically have modules that contain
the machinery to complete a given function. Term
limits If a cell continues down a given path
for a long period, there
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Cells Have Different Phases for Different
Functions
Specialized Functions Require Phase Change Many
functions of cells are so complex that the phase
of the cell must be altered through changes in
state of many proteins or expression. Phase
Changes Are Discontinuous Cells appear most
often to undergo a rapid switch from one phase to
another with the appropriate signal.
Populations of Clonal Cells Can Be in Many
Phases Even though a group of cells originated
from the same cell and are grown in the same
medium, they can be in different phases.
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Phases of the cell cycle are bounded by definite
checkpoints that aid in making the transitions
abrupt.
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The Critical Function of Cells is to Propagate DNA
DNA Encodes Plan for the Organism Survival of
the organism means propagation of the
DNA. Information Exchange is Critical for
Survival When one organism in a population has
a mutation that enables it to survive a
challenge, others will potentially benefit by
sharing that information.
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Parasitic Relationships Exist at Many Levels
Not All Small Organisms Are the Food of Larger
Ones Many small organisms can survive with
material that they obtain from larger
organisms. Subcellular Parasites Cannot Survive
Outside the Cell Bacteriophage and viruses have
found ways to propagate their DNA (RNA) through
co-opting many functions of the cells that
propagate them.
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Reading for next lecture Molecular Biology of
the Cell, Alberts et al., 4th Edition Chapter 25
Pathogens