Download Fall 2011 Prelim 1 BioG 1440 Introduction to Comparative

Fall 2011 Prelim 1
BioG 1440 Introduction to Comparative Physiology
Instructions:
1) Please use a #2 pencil only for the optical-scan answer sheets. Fill in each circle completely
2) Fill in your last name and first name on the BLUE op-scan sheet as in the following example.
Leave a space between last and first names. Blacken the corresponding letters below in
pencil as shown below.
3) Under BIRTH DATE, enter your 4-digit study group number (eg. 2031 or 2143); blacken the
appropriate circles below each number.
4) Starting in column A under IDENTIFICATION NUMBER enter your 7-digit Cornell ID number
(dropping off the leading 00). Leave no blanks between numbers; blacken the appropriate
circles below each number as in the example.
5) Leave the SPECIAL CODES COLUMNS blank.
6) After you have completed these steps, wait until instructed by your TA to begin the exam
Scoring: Correct answers will receive one point. “Don’t Know” answers will receive 0 points.
Incorrect or blank answers will receive a penalty of -0.25 point. Thus it is to your advantage
to indicate when you really do not know the answer rather than guessing.
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The diagram below shows the effects of blood glucose levels on insulin secretion. When blood glucose
is above 110 mg/100 ml, insulin is secreted. Blood glucose is increased by eating.
1) As a result of eating a meal,
increasing blood glucose causes
the insulin level in the blood to rise
because of positive feedback.
(True/False/ Don’t Know)
2) As glucose is taken up by the liver
and body cells, the production of
insulin by the pancreas declines.
(True/False/Don't Know)
3) As the glucose returns to 110
mg/100 ml, the concentration of
insulin in the blood declines.
(True/False/Don’t Know)
Consider the two containers shown to
the right. Each container is separated by
a semi-permeable membrane (dashed
line). Container 1 is filled with 1 M each
of the ions X+ and A- on the left, and 1M
each of Y+ and A- on the right. Container
2 is filled with a 1 M solution of glucose
(gluc) on the left and pure water on the
right. Recall that water potential is the
free energy of water.
The membrane in container 1 is only
permeable to X+ and the membrane in
container 2 is only permeable to glucose.
4) At equilibrium, the concentration of X+ on the right side of container 1 will be equal to the
concentration of glucose on the right side of container 2. (True/False/Don’t Know)
Now suppose that the membranes in both containers are permeable to water only.
5) The left side of container 2 has a lower free water concentration than the right side.
(True/False/Don’t Know)
6) There is a water potential gradient across the membrane of container 1. (True/False/Don’t Know)
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7) A plant cell is dropped into the left side of container 2. The cell swells to a certain volume and then
stops swelling. At this point, no molecules are being exchanged between the cell and the liquid in
the container. (True/False/Don’t Know)
Cellular respiration consists of three groups of reactions: glycolysis, the citric acid cycle, and oxidative
phosphorylation. These three groups of reactions are not independent of each other but are coupled
together by several different compounds. As a consequence of this coupling,
8) under anaerobic (no O2) conditions, glycolysis will stop unless NADH produced by glycolysis can be
oxidized by some process other than oxidative phosphorylation. (True/False/Don’t Know)
9) ATP produced by all three groups of reactions feedback inhibits reactions in the early steps of
glycolysis, thus regulating the cell’s production of ATP. (True/False/Don’t Know)
10) some of the energy for chemiosmotic ATP synthesis is carried from glycolysis to oxidative
phosphorylation in the form of NADH. (True/False/Don’t Know)
The outer surface of most cells contains many glycoproteins, membrane proteins with attached
carbohydrates that face the exterior of the cell. These carbohydrates are attached to the proteins
when the proteins are located in the membrane of the Golgi apparatus. The proteins are then
transported to the plasma membrane in small vesicles that bud off the Golgi membrane and fuse with
the plasma membrane.
11) When these proteins are in the Golgi membrane, the carbohydrates are attached to the protein on
the side of the membrane facing the cytoplasm. (True/False/Don’t Know)
The lipid composition of membranes from fish that live in cold
water is different from the same fish that live in warmer
water. Fish in cold environments have a higher amount of
unsaturated fats when compared to fish in warmer
environments. Recall that unsaturated fatty acids contain one
or more double bonds in either the cis or trans configurations
(see examples to right).
12) If the composition of membranes does not change, lower
temperature results in lower fluidity of membranes.
(True/False/Don’t Know)
13) Shorter hydrophobic tails on the fatty acids will keep membranes more fluid at lower temperature.
(True/False/Don’t Know)
14) Increased number of unsaturated fatty acids will keep membranes more fluid at lower
temperatures. (True/False/Don’t Know)
15) Trans fatty acids are more common in the membranes of cold water fish than cis fatty acids.
(True/False/Don’t Know)
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Fish living in cold waters produce a diverse group of glycoproteins called antifreeze proteins (AFPs).
These proteins bind to the surfaces of tiny ice crystals forming in fish’s blood, preventing the crystals
from growing and causing damage to the blood and body tissues. Binding of the AFPs to these ice
crystals has been shown to be a quickly reversible process. Studies have also shown that some types
of AFPs are rich in the amino acids alanine and threonine (structures below), but scientists are still
unsure of the mechanism of AFP binding to ice crystals.
16) The binding of AFPs to ice crystals could be decreased by decreasing the AFP concentration in the
blood. (True, False, Don’t Know)
17) The site at which ice crystals bind to AFP is lined with alanine residues (True/False/Don’t Know)
18) Hydrophobic interactions contribute significantly to determining AFP tertiary structure. (True, False,
Don’t Know)
19) Another protein that competes with ice crystals for the binding site on AFPs would have a surface
covered in nonpolar amino acids. (True, False, Don’t Know)
Consider a biological reaction that has a positive G. The energy required for this reaction to occur (to
convert reactants into products) is supplied by the hydrolysis of ATP to ADP and Pi.
20) One role of the enzyme that catalyzes this reaction is to couple the energy release by ATP hydrolysis
at one site on the enzyme to the energy requiring reaction at a different site on the same enzyme.
(True, False, Don’t Know)
21) Another role of the enzyme is to use the energy of ATP hydrolysis to provide the activation energy
for the reaction, eliminating the need for thermal energy to drive the reaction. (True, False, Don’t
Know)
While animal cells have the sodium/potassium pump as their main electrogenic pump in the plasma
membrane, bacteria and plant cells have an electrogenic proton pump which pumps protons (H+) out
of the cell. Because of this,
22) the membrane potential of animal cells is negative and the membrane potential of plants and
bacteria is positive. (True, False, Don’t Know)
23) there would be no driving force for the movement of K+ ions through open K+ channels in the
plasma membrane of plants or bacteria. (True, False, Don’t Know)
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24) the presence of non-permeable negative charges inside cells would oppose the H+ pump in plants
and bacteria, but facilitate the sodium-potassium pump in animal cells. (True, False, Don’t Know)
Lysine and arginine are amino acids whose R groups both have a positive charge at physiological pH
and are nearly identical in size and shape. Consider an enzyme where a lysine is located in the active
site of the enzyme and plays a role in binding of the substrate to the enzyme. The enzyme also
contains a single alpha helix, which is located 50 amino acids away from the lysine. A mutation causes
a lysine residue to change to an arginine. The mutation of the lysine to an arginine will
25) probably render the enzyme non-functional. (True, False, Don’t Know)
26) alter the proteins' primary, secondary, and tertiary structure. (True, False, Don’t Know)
27) change the pH optimum of the enzyme by several pH units. (True, False, Don’t Know)
Most of the ATP produced by cellular respiration is made by oxidative phosphorylation, a three step
process in which electron transport from NADH to O2 is coupled to pumping of protons across the
inner mitochondrial membrane, which in turn is coupled to the synthesis of ATP.
28) If an artificial proton channel is inserted into the inner mitochondrial membrane, ATP synthesis will
stop but electron transport between NADH and O2 will continue. (True/False/Don't Know)
29) Changes in the structure of the ATP synthase complex (the enzyme that makes ATP) couple the
energy released by electron transport to the energy requirement of ATP synthesis. (True, False,
Don’t Know)
30) The G for electron transport in oxidative phosphorylation is negative because the free energy for
the loss of electrons from NADH is greater than the free energy for the gain of electrons by O2.
(True, False, Don’t Know)
Secondary structural elements (alpha helices and beta sheets) are stabilized by a regular pattern of
hydrogen bonds between atoms that are part of the peptide backbone. Because of this,
31) R groups play no role in determining where alpha helices and beta sheets from in the overall protein
structure. (True, False, Don’t Know)
Using the Michaelis-Menton plot (right), which shows
the reaction rate of the same enzyme measured under
two different conditions (A and B), determine the
validity of the following statements.
32) Curve B shows a higher affinity for the substrate than
curve A. (True, False, Don’t Know)
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33) The difference in the curves is most likely due to a conformational change caused by the differences
in the environment of the enzyme under the two conditions. (True, False, Don’t Know)
34) The differences in the maximum rate under each condition must be due to differences in the
concentration of the enzyme. (True, False, Don’t Know)
35) The conditions represented by curve B are most likely to be closest to those found in the cell where
this enzyme normally functions. (True, False, Don’t Know)
A negative allosteric regulator is a molecule that stabilizes the inactive (or less active) form of an
enzyme. Many drugs mimic the effect of negative allosteric regulators. To do this, the drugs must
36) bind to the active site of the enzyme. (True, False, Don’t Know)
37) induce a conformational change in the enzyme. (True, False, Don’t Know)
The plasma membranes of animal cells contain an electrogenic sodium-potassium pump which pumps
3 Na+ out and 2 K+ into the cell per ATP hydrolyzed. If there were no other transport proteins for ions
in the plasma membrane,
38) the energy available from moving on Na+ into the cell would be the same as the energy available
from moving one K+ out of the cell. (True, False, Don’t Know)
39) the membrane potential of the cell would be closer to the equilibrium (Nernst) potential of K+ and
farther from the equilibrium potential of Na+. (True, False, Don’t Know)
The following statements refer the graph to the right,
which shows how the rate of passive diffusion of a
substance across a membrane is influenced by X. Note
that the meaning of X changes among the statements.
40) If X is the size of the concentration gradient of the
substance across a membrane, curve A could represent
the rate of diffusion measured at a higher temperature
than curve B. (True, False, Don’t Know)
41) The data plotted in curves A and B are consistent with
what one would expect if X was membrane thickness. (True, False, Don’t Know)
42) The curves A and B represent the diffusion of two different substances across a membrane. X is the
number of transport proteins for each substance in the membrane. These data are consistent with
the substance in curve A having a greater lipid solubility than the substance in curve B. (True, False,
Don’t Know)
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