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In the final portion of the semester, we have drawn together all the concepts from earlier in the semester to described the differentiation and organization of some important cell types found in multicellular organisms. Some cell types we discussed were general such as epithelial cells, connective tissue cells, neurons, and muscle cells, and some were specific cell types such as embryonic stem cells, cancer cells, and white blood cells such as B cells.
Different cell types express different genes. Expressing different genes results in different proteins expressed in different abundances. Differences in protein expression and abundance cause cells to carry out different activities, assume different shapes, and exhibit responsiveness to different stimuli.
In Cells and Genes, you have learned enough about the cellular and molecular
mechanisms of life to know
- what are the classes and properties of the macromolecules from which cells
are made
- what are the relative sizes of biomolecules and organelles made from those
macromolecules
- how cells respond to the world around them (through trans-membrane receptor
singling)
- how cells may change their activities (their behaviors) in response to
stimuli from their environments (by changing expression of key genes so a
new behavior is possible, for example).
- how an organism can be influenced by changes in the behavior of its cells
(by activating its white blood cells to fight off an infection, for example).
For any of the general cell types we discussed, be able to describe a hypothetical series of events that *could* feasibly occur to take any of these cell types through a response to an extracellular stimulus.
For example: Describe a signaling pathway that could trigger a pancreatic
Beta cell, stimulated by glucose in the blood, to begin to transcribe and
eventually secrete insulin. What has to happen at the cell surface
to create a response inside the cell? What might that response *be*
in the cytoplasm to cause changes in transcription? What changes in
trascription will occur? What will happen back in the cytoplasm after
transcription change in the nucleus? What will the final result be
back at the cell surface after all these intracellular changes take place?
You should be able to include in your answer, in roughly this order, the
following terms. This is not a complete list. By using these terms however,
you will get an idea of how to tell a story of cell signaling and response
that accurately reflects current understanding in cell and molecular biology.
Phospholipid bilayer, plasma membrane, protein receptors, trans-membrane
signaling, G-proteins, cAMP, kinase cascade, amplification, diffusion, nuclear
pore, transcription, enhancer, repressor, promoter, transcription initiation
machinery, TFIID etc, primary transcript, intron, exon, nuclear pore, ribosome,
translation, codons, genetic code, cytoplasm, rough ER, smooth ER, Golgi,
microtubules, centrioles, motor proteins, mitochondria, respiration, glycolysis,
Krebs cycle, lysosomes, endosomes, endocytosis, cell-cell contacts, exocyosis,
actin cortex, etc.
Quiz each other. Start with a cell type (neuron, muscle cell, epithelial
cell, connective tissue cell) and a stimulus (any relevant ligand) and a
change that cell might undergo (change in transcription, or change in secretion,
or change in cell cycle state, etc) and try to create a series of molecular
events that would connect those ingredients. Dare each other to describe
how any one cell type (you pick the cell or cell type) responds to any stimulus
(you pick the stimulus and the intracellular signaling pathway) and exhibits
a change in activity (you pick the activity). I would be happy to discuss
with you any hypothetical pathway you generate.
Content and design of this site by Dr. Bob Morris. Please direct
comments to him at rmorris@wheatonma.edu.
Last updated 04/30/2004.