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Tutor profile: Alex L.

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Alex L.
STEM science tutor with graduate level teaching experience
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Questions

Subject: Health and Medicine

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Question:

In apoptosis, the cell destroys itself from within and avoids leakage of the cell contents into the extracellular space. What might be the consequences if programmed cell death were not achieved in so neat and orderly a fashion?

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Alex L.
Answer:

There are two main ways in which researchers categorize cell death. These are planned and “organized”, Apoptosis, or due to trauma and “messy”, necrosis. Apoptosis plays a major role in development when balancing out cell division rates and cell death rates. This can keep the concentration of cells at a roughly even homeostasis. There are in fact numerous diseases such as cancers and inflammatory conditions that arise when apoptosis isn’t able to balance these rates. When a cell undergoes apoptosis it performs certain action in preparation so as to not let it’s death affect the longevity of neighboring cells. Some of these preparations include condensation of the cytoplasm and the nucleus, disassembly of the DNA, maintenance of cell membrane and expression of transmembrane proteins which signal to phagocytic cells to engulf the dying cell. These simple tasks a cell does before programmed cell death are used to prevent the contents of the cell from leaking into the ECM. When cell death is not predetermined or signaled for the cell does not have a chance to do any of these things and the ECM is then flooded with inflammatory contents leak out. This could be incredibly dangerous to the health of the neighboring cells as the contents could include viral vectors or proteins that could create harmful signals if bound the correct transmembrane protein. One example of this is necrotizing fasciitis, in which cell necrosis spreads from an origin and damages neighboring cells.

Subject: Biology

TutorMe
Question:

When cells enter mitosis, their existing array of cytoplasmic microtubules has to be rapidly broken down and replaced with the mitotic spindle, which pulls the chromosomes into the daughter cells. The enzyme katanin, named after the Japanese samurai swords, is activated during the onset of mitosis and cleaves microtubules into short pieces. What do you suppose is the fate of the microtubule fragments created by katanin?

Inactive
Alex L.
Answer:

Katanin is a unique enzyme which hydrolyzes ATP to break up the bonds of microtubules in preparation for the later stages of mitosis. By breaking up a larger portion of the cytoskeleton Katanin has not only created room for the new daughter cells to separate but also created resources for the formation of the astral microtubules, kinetochore microtubules, as well as the interpolar microtubules of the mitotic spindle. Along with this all the energy that is freed from the hydrolysis of ATP can be used by the cell in order to pay the immense energetic cost of mitosis. On top of all this the remaining microtubules while much shorter are also much more dynamic which will aid in the formation of the cytoskeleton for the new daughter cells after anaphase.

Subject: Anatomy

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Question:

While putting metal panels on the roof of a barn, one of the panels slips out of the hands of the man on the roof. During an attempt to catch the panel, a worker below is struck by its sharp edge. The panel hits across the anterior surface of his right arm at mid length and the impact severs all of the tissue to the bone. When examined in the emergency room it is noted that the patient can only weakly flex his elbow and the lateral side of his forearm is numb. In addition to the muscles, which nerve is injured? What nerve is affected? What are the roots involved? What other symptoms do you expect to be present?

Inactive
Alex L.
Answer:

The nerve affected is the musculocutaneous nerve. The roots involved with this nerve are C5-C7 into the lateral cord. You would expect weakness in the supinator muscles, the biceps, the brachialis, the coracobrachialis and typical lower motor neuron signs.

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