25 Jun What type of control mechanism is described here
Question
SAMPLE QUESTIONS- EXAM 1
1.- As plasma Ca2+ concentration goes below 2.1 mM, decreased activation of calcium-sensing plasma
membrane receptors (CaSR) induces cells at the parathyroid gland to secrete parathyroid hormone (PTH).
In response to PTH, the kidneys decrease the amount of Ca 2+ excreted into urine, and osteoclast cells in
bone begin to release Ca2+ into plasma.
What type of control mechanism is described here? Be precise!
Draw a diagram identifying all elements involved (i.e., control center, etc.)
During early stages of acute hypomagnesemia PTH levels in plasma increase, but in later stages,
PTH end-organ resistance ensues. Using your diagram, predict what will be the effect of such
PTH resistance on Calcium metabolism.
2.- High plasma glucose triggers beta cells in the pancreas to secrete insulin. Liver cells respond to insulin
by taking glucose and storing it as glycogen, restoring normal glucose levels.
What type of control mechanism is this?
Draw a diagram identifying all elements taking part in this mechanism.
Use your diagram to explain the differences between type 1 and type 2 diabetes.
3.- Which type of bond holds atoms together in baking soda? Now you place baking soda in water and
stir it. As baking soda dissolves, what chemical bonds are breaking down? Which ones stay unchanged?
What chemical bonds are being created? What chemical bonds exist the final solution? Consider both
solute-solvent and solvent-solvent interactions, in addition to chemical bonds holding polyatomic ions
together.
4.- A 1 L saline solution is maintained inside an incubator containing 5% CO2 / 95% air, so CO 2 goes into
solution until an equilibrium is achieved. Write the equilibrium equation for the reaction of CO 2 with
water. Will the pH of this solution be acidic, basic, or neutral?
Next, you add 1 g of NaHCO3 and stir it. What will happen to the NaHCO 3 in solution? Does the pH of the
solution increase, decrease or stay the same? Use your equation to justify your response.
5.- Draw a diagram of a phospholipid and indicate what areas of the molecule are polar, non-polar,
hydrophilic or hydrophobic.
6.- Do all proteins have a primary, secondary, tertiary and quaternary structure? Justify your response.
7.- An average human has 3 L of plasma, 12 L of interstitial fluid and 40 L of intracellular fluid. Which
compartment contains more ionic calcium, the intracellular or the extracellular compartment? Consider
that ionic calcium is 50% of total plasma calcium. Show your numbers to justify your response.
8.- Outline the biosynthetic and degradation pathways followed by a membrane protein that a) folds
correctly, or b) fails to attain its correct final structure. Make sure of specifying all organelles involved in
both biosynthetic pathways.
9.- Draw a diagram showing all different types of intercellular junctions that you may find in an
epithelium and describe their functions. In your diagram, show the different membrane domains that
can be distinguish in epithelial cells.
10.- What is the difference between an endocrine and an exocrine gland? How can such diverse
structures develop from a common precursor epithelium?
11.- Produce a graphic representing free energy vs. time in an endergonic reaction, in the presence and
absence of a catalyzer. In your graphic, show how would the presence of an enzyme affect this reaction?
12.- Muscle tissue uses both aerobic and anaerobic pathways. Produce an outline of the metabolism of
muscle tissue during moderate (aerobic) and intense (anaerobic) exercise, and discuss the advantages
and disadvantages of switching to a predominantly anaerobic metabolism.
13.- Write the reaction catalyzed by a kinase. How does it differ from that catalyzed by a phosphatase?
14.- Indicate all ways in which a cell could regulate a metabolic pathway.
15.- Explain the different transport mechanisms that mediate distribution of water across the body, from
the moment you drink a glass of water, to the moment water enters cells located in different organs.
16.- What properties do all protein-mediated transport mechanisms share? Does osmosis share these
properties?
17.- Produce a diagram of the Na,K-ATPase in a cell membrane. Indicate how many ions move in each
direction. What is the source of energy for this transport mechanism?
Using your diagram, explain how the Na,K-ATPase helps create the cell membrane potential. Why are K +
channels also required in order to create and maintain the cell membrane potential?
18.- Explain the differences between active transport and secondary active transport in terms of
gradients. Produce a diagram illustrating these differences.
19.- Using the diagram below, explain how this epithelium could transport glucose and sodium from the
lumen to the interstitial fluid bathing the basolateral membrane. Make sure to insert all membrane
proteins required for this function. Consider that luminal [glucose] is lower than intracellular [glucose].
Finally, low temperature is known to inhibit the Na,K-ATPase. Use your diagram in order to predict how
incubation at 20oC would affect glucose transport during a 15 minutes lapse of time.
20.- In a 1 ml sample of human saliva you found 0.87 mg of NaCl (F.W= 58 g/mol) and 1.5 mg of KCl (F.W=
75 g/mol). Is saliva hypotonic, isotonic or hypertonic? What would happen to human cells if exposed to
saliva? Show your work and justify all your responses.
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