Question (1) :
ND0922b EGTA chelates Ca2+ with high affinity and
specificity. How would microinjection
Answer :
EGTA, by chelating Ca2+, would be expected to interfere with signaling
pathways that use Ca2+ as a second messenger. Glucagon triggers glycogen
breakdown in liver via a cyclic AMP pathway and thus would not be affected by
EGTA. By contrast, vasopressin signals glycogen breakdown via a Ca2+ pathway and
would be blocked by injection of EGTA.
Question (2) :
ND0904.B: Rb is one example of a category of
anti-proliferative genes in humans
Answer :
b.
Antiproliferative genes such as Rb encode proteins that stop the cell cycle.
During normal cell division, these proteins must be turned off. If they were
overexpressed in all cells, it is likely that the machinery that keeps these
proteins turned off would be overwhelmed, and cell division would stop. Thus,
this cure for cancer might be successful but the patient would be dead.
--------------------please draw the schematic diagram from the text
Question (3) :
ND0910b The 10 reaction steps that make up the
glycolytic pathway are found in most living cells
Answer :
The
extreme conservation of glycolysis is one form of evidence that all present
cells are derived from a common ancestor. In this view the elegant reactions of
glycolysis would have evolved only once, and then they would have been inherited
as cells evolved. The later invention of oxidative phosphorylation allowed 15
times more energy to be captured than is possible by glycolysis alone. This
remarkable efficiency is close to the theoretical limit and hence virtually
eliminates the opportunity for further improvements. The generation of
alternative pathways would result in no obvious growth advantage that could have
been selected in evolution.
Question (4) :
ND0911b How do you suppose that a molecule of hemoglobin
is able to
Answer :
At the simplest level, hemoglobin binds oxygen efficiently in the lungs
because the concentration (partial pressure) of oxygen is highest there. In the
tissues the concentration of oxygen is lower because it is constantly being
consumed in metabolism. Thus, hemoglobin will tend to release (bind less) oxygen
in the tissues. This natural tendency—an effect on the binding equilibrium—is
enhanced by allosteric interactions among the four subunits of the hemoglobin
molecule. As a consequence, much more oxygen is released in the tissues than
would be predicted by a simple binding equilibrium.
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